Guabonito Times

Pluto Relegated to Second-class citizen

2006-08-24T13:26:00.000-07:00

My name is Jason Perry, and I'm here to tell you the truth.

Today, the International Astronomical Union made a mistake by demoting Pluto from a planet to a "dwarf" planet, a second-class citizen of the Solar System. Rather than basing their decision on the nature of the object in question, they included a discriminatory stipulation that a planet "must clear the neighborhood around its orbit". And rather than stick with this abomimation of a definition, they further go on to stipulate that 8 objects apparently fit this definition. This elitist attitude to our icy brothers and sisters is gross and tragic error that must be corrected. This defintion would not only prevent Pluto from being a planet, but would prevent currently undiscovered objects beyond Neptune larger than the current smallest, so-called "planet", Mercury, from being a planet.

I say that it is none of the IAU's business what a planet commingles with. Whether it is a gas planet with trojan asteroids, terrestrial "planets" with smaller "asteroids", or an icy "planet" with other icy objects. I say we stand up with our icy breathern and fight this embarrasing definition.

Viva las lunas rojas!

The Return/The Olympics/Lucilla

2006-02-13T12:46:00.000-07:00

It's nice to be back here after a 5 month absence. This blog will no longer be on the Cassini mission and news on various satellites of Saturn, but will be about me. Basically, I am replacing "Ionian Journal", a second blog I had but never updated, with this one. I changed the name of this blog to reflect this change, though Guabonito is still a Titan related name. Guabonito is a broken ring of bright material in eastern Shangri-la on Titan.

So, it is good to be back. This weekend, I officially started my Olympics addiction. Every 2 years, I become glued to the TV to watch arcane sports like nordic combined (wow, jumping 100 meters on skis, then racing 9 miles on skis), water polo (like basketball in a pool), and short-track speed skating (roller derby on ice). What is it about the Olympics that compels people to watch sports that they wouldn't watch at another time but the Olympics. I'm sorry, but if there was a nordic combined competition on, I would watch it unless I had a gun pointed at me. Granted I still won't watch figure skating (prancing around on ice, no matter how many times you can spin around, is NOT a sport), but yet now I want to watch luge (but not two-man luge, that just seems wrong for some reason), snowboarding, downhill alpine skiing, etc. Maybe NBC Universal puts something in the water supply...

Lucilla, my 9-month old Bell albino leopard gecko, is finally eating again after taking a month off. She ate a few times over the last month, but usually it wasn't sustained, maybe eating one or two crickets here and there. I finally figured that it was partly my fault. See, I would put the dusted crickets in a food dish, sans there back legs and their front legs to keep them from escaping the disk. However, this often ilmobilized them more than I wanted, and by the time Lucilla was interested in hunting, the crickets barely moved. Geckos hunt using the movement of their prey to key on them before striking (think T-rex in Jurassic Park) so this lack of movement caused Lucilla to not be interested in them. So last night, I waited for Lucilla to go into hunt mode (her eyes become dilated, she stares out her hide, focusing on my movements), threw four unmolested (except for the dusting) crickets into her cage, and she went after them. She ended up bagging three of the four. Good for her. She certainly looked happy after getting some hunting in.

That's all I have for now.

The End Part II

2005-09-17T08:17:00.000-07:00

Okay this really is the last post. I just want to nip in the bud, right here, right now, shutting down this site was my idea. No one, and I mean no one, asked me to shut it down. I received some comments regarding some top level manager's opinion on my recent posts on the T7 issues (which I should point were temporary and have been fixed). It was a mistake for me to even discuss them here, even in the vague manner I tried to convey, and their disapproval was brought to my attention. This issue scared me. It was fun when this site was just a small group of people who wanted to hear the latest from Cassini. But if I need to be concerned about what I write, then it becomes less fun. I love what I do, I can't imagine myself doing any better at this point in my life, and I will not jeopardize it for a blog. I'm sorry, but I won't. And rather than look over my shoulder and wonder if what I just sent is kosher with everyone who are higher up than me, I'd rather just end this page. I apologize to all those who have come to rely on this page. I really do. Don't stop caring about the Cassini mission just because I'm not here to blog about it.

Now, that's not to say I am completely going away. Last night, I decided rather than give up here and do nothing with volcanopele.blogspot.com, I will just change the format. I have had this novel, essentially in my head for 5 years now, waiting for me to actually commit it to paper. I've decided to write it here on this blog. I'm not sure how this will work but I think it will be an interesting experiment. Based on similar projects on Blogger, I will post a segment of the novel every few days, once a week or so, on a post. It could be a chapter, it could be more, it could be less. I personally like that concept. So I am going to give it a try. So on September 24, this blog will be replaced by "Afterword". I hope some of you come back for that.

The End

2005-09-16T16:16:00.000-07:00

This will be the last post of this blog. I know a lot of you have come to rely on this site for information on the Cassini mission, but it appears that I will no longer be able to continue posting here. Ironically, this site was killed by its success. This site was read not only by people in the public, but by those in the Cassini project as well. I knew full well of this, but apparently I crossed a line with one of my posts last week, and they called me (litterally) on it. This site was only going to stay up as long as I got something out of it and you did too. Now, this site has become a lot less fun. So, effective immediately, I will no longer be posting on this blog. I will probably post occasionally on the Unmanned Spaceflight.com forum, but will likely become a lurker. I will keep the site up for the next week, when I will then shut it down for good :-(

New Titan Image: Canyonlands on Titan

2005-09-16T15:00:00.000-07:00

The Cassini RADAR team released this view of Titan taken last week during the T7 flyby. This cutout from their SAR noodle is located near 55 degrees South, 7.5 degrees West and is approximately 300 km long. Unlike the previous image, the channels in this region consist of long valleys (up to 200 km long and 200 meters deep) that have only a few tributaries. These channels are more akin to river systems on earth rather than the arroyos seen in the T3 swath and in the previous image.

New Titan Image: Titan's Rain Drains to the Plains

2005-09-16T14:45:00.000-07:00

This is the second of three views released by the Cassini RADAR team showing portions of the RADAR SAR swath returned last week. This portion is from south central Tsegihi near 48 degrees South, 14 degrees West. This view extends 240 kilometers from left to right. At top, you can see a deeply incised channel flowing from a region of bright, rough terrain down to darker, smoother material. This fits with the view that methane rains wash material from the bright highlands down to darker plains. Near the bottom of the image, there is a branching network of channels, with the widths of the channels varying. These properties are suggestive of rainfall run-off channels rather than river networks.

Still, note how well this liquid has eroded these channels. These are quite deeply incised, suggesting either that the liquid efficiently erodes the bedrock, or these channels have been active for a good percentage of geologic time.

New Titan Image: Shoreline on Titan?

2005-09-16T14:33:00.000-07:00

The RADAR team on Cassini has released some of their SAR swath taken on September 7. I will post my comments on all three cut outs. This portion is near the very end of the part the were able to get back. The second half was lost. This portion shows a possible shoreline in the central part of the dark albedo feature known as Mezzoramia. On the left, you can see terrain that is suggestive of erosion by liquids, with alcoves and scarps. At right, the surface is quite dark suggesting that the area is much smoother than any other place so far looked on Titan by Cassini RADAR. Many of the bright features that bound this terrain are similar to shoreline terrain on Earth.

This portion of the swath is from 66 South, 356 West in central Mezzoramia. This portion is 330 km wide and 175 km tall.

Cassini Significant Events for 09/08/05 - 09/14/05

2005-09-16T11:06:00.000-07:00

Haven't mentioned one of these in a while, but this week's Cassini Status update is now online. Regarding the mishap during last week's Titan flyby:

A significant amount of science data was lost during the recent Titan flyby as a result of an operational problem at the DSN tracking station, and a software error on the spacecraft. The software error was the larger contributor of the two causes, and the data loss resulted from an improperly set flag preventing the spacecraft from writing to or reading from the A side of the solid state recorder, so the result was performing the encounter with only half of the expected data storage volume. Commands will be sent on September 15 to reset the flag to its proper value, and normal operation is expected after this. The nature of the code error is now fully understood and has been reproduced in the spacecraft test bed. A decision will be made in the near future whether to correct the flight code or to implement workarounds to prevent the conditions that led to execution of the faulty code.

These problems led to the loss of all data after 1 minute prior to closest approach (because the "B" recorder was full at that point) as well as our high resolution mosaic, VIMS' medium resolution mosaic, and the RADAR inbound altimetry data. We did, however, obtain our global mosaic (a portion was released publically earlier this week) and RADAR received a portion of their SAR swath over central Tsegihi, Mezzoramia, and some features a little farther to the east.

New Telesto Image: Squinting at Telesto

2005-09-14T10:32:00.000-07:00

CICLOPS has released this processed view of Telesto, taken on August 1 from a distance of 768,000 km. From that distance, the 24-km wide Telesto appears as nothing more than a blog of light with no discernable features or shape. Believe it or not, this qualifies it as one of the best images of Telesto thus far (Voyager's best image was ~ 5km/pixel) But, fear not, better images of Telesto are coming. Cassini comes within 9800 km of this small, trojan satellite on October 11, 2005. This will be one of the closest flybys of a small satellite during the tour. At closest approaches, images with a resolution of 56 m/pixel are possible (~425 pixels across Telesto's disk).

Off-topic: Cassini finally sees spokes in Saturn's B-ring

2005-09-13T14:45:00.000-07:00

Not exactly satellite-related, but as has been alluded to on a few discussion sites in the past week, the Cassini Imaging team announced today that they had finally observed the spokes, first seen by Voyager but had not been seen by Cassini. The spokes appear to be bright wispy features on the B-ring in the above image and in the images released today. These images are of the unlit side of the ring, so the B-ring appears dark due to its opacity and the C-ring, at lower left, appears bright. Saturn's limb can be seen toward the upper left corner. Pretty neat stuff.

New Titan Image: Monitoring Fensal-Aztlan

2005-09-13T11:13:00.000-07:00

CICLOPS has released this mosaic of the Fensal-Aztlan (formerly known as the "H") region on Titan. Fensal is the northern branch of the "H". Fensal has some subtle brightness variations and has quite a few bright spots, or "islands", dotting the region. Their distribution appears to be more scattered than similar sized bright spots in Shangri-la, west of Xanadu. There, the spots were clustered into several "archipelagoes" and aligned in a similar fashion, usually east-west. The spots in Fensal don't seem to have a prefered orientation. A few larger bright spots can be seen in Fensal, including Bazaruto Facula on its eastern end.

Aztlan, the southern branch of the H plus the dark region surrounding Elba Facula to the east (not in this particular crop), has far fewer smaller islands, but does have several large islands, including Sotra Facula, a 240 by 120 km sized bright feature just right of center in the lower left frame, and Coats Facula, a smaller island to the east of Sotra.

This mosaic is just 4 frames within a larger, 20-frame mosaic to be released later. This mosaic was taken during last week's T7 encounter.

DPS Titan News

2005-09-12T12:03:00.000-07:00

Emily Lakdawalla at the Planetary Society has posted on her blog quite a few notes from the Titan DPS talks. Unfortunately, not much is news to me so it is rather difficult for me to remember what has been publically mentioned and what is new. It is a great read and and I definitely recommend checking it out.

New Rhea Image: Frame-Filling Rhea

2005-09-09T13:40:00.000-07:00

CICLOPS today released this processed image of Rhea taken on August 1, 2005. This image was taken from a distance of 255,000 km and has a resolution of 1.5 km/pixel. As the title suggestion, this image was taken when Rhea nearly filed the entire narrow-angle camera field-of-view. Nothing shocking from Rhea, just lots and lots of craters (with a few fractures up at the top toward Rhea's wispy terrain). This image primarily shows the southern trailing hemisphere of Rhea. Two prominent impact basins, ~300 km across can be seen along the terminator. The top basin is unnamed but the second basin is Izanagi. This basin was the site of one of the pre-launch artwork done for the Cassini mission. No sign of the fractures shown in that rendition.

T7 Coverage Map

2005-09-07T19:06:00.000-07:00

CICLOPS has released the coverage map for today's flyby of Titan. Cassini ISS will examine the sub-Saturnian hemisphere of Titan, particularly around the Fensal-Aztlan region (formerly known as the "H"). The coverage for this encounter will primarily come from two mosaics. The first, MONITORNA001 outlined in green, is a 2 km/pixel mosaic over the entire visible disk. This is similar to other full-disk mosaics from Ta and T3. The second mosaic, COMBINED001 outlined in red and yellow, is a higher resolution mosaic consisting of many images near the center of the visible disk. Key targets for this mosaic include features within Fensal, Aztlan, Quivira, and northern Tsegihi regions, such as Bazaruto Facula (with its 80-km central crater), Omacatl Macula, and the debris deposit in northeast Aztlan that bisects Quivira.

A map showing RADAR SAR coverage is also available.

New Dione Image: Older Southern Fractures?

2005-09-07T17:39:00.000-07:00

CICLOPS released today this processed view of Dione on August 1. This image was taken from a distance of 269,000 km and has a resolution of 2 km/pixel. The wispy terrain of Dione can be seen toward the top with Padua Linea running from top center to right and Palantine Linea running along the terminator at left. In contrast to these relatively sharp fractures, the fracture systems near the south pole, just to the left of the large impact basin, have relatively subdued topography and are probably older than the fractures that make up the wispy terrrain. The radial feature near the center of the disk, Cassandra, was thought to be caused by a ray crater, but analysis of the topography associated with the feature now shows that Cassandra likely has a tectonic origin.

Note the two craters just to the left of Cassandra. These craters have a similar shape to Ali Baba and Aladdin craters on Enceladus, perhaps indicating local heating in that region of Dione, in order to produce the viscous relaxation we observe.

New Look

2005-09-07T09:46:00.000-07:00

The formatting and column issues have bothered me (and others) for the last time. I have switched to a different template within Blogger to see if that helps, but a few features from the old template, like recent posts, are now gone :( I will try to fix that soon enough.

Titan-7 Flyby Info

2005-09-06T14:59:00.000-07:00

View of Titan from Cassini 2 hours into ISS' high resolution observation, about 3 hours prior to closest approach (sub-spacecraft point=4.4N, 26.2W). The plot was generated in GISS' Titan 24 software. The map is derived from ISS map released in March (ask for full version used here, just adds blank space north of 34N). The full version of above plot is available as well as one with feature labels. The data for plot was obtained from Mission description document.

T7 Quick-facts:

Closest approach occurs on September 7 at 1:33 am PDT
Closest Approach Distance = 1075 km (bumped up from 950 km)
Relative speed WRT Titan = 5.9 km/sec
Closest Approach Lat and lon = 67 South, 308.1 West
South Polar Pass with sub-Saturnian hemisphere visible inbound
Outbound flyby (sunlit inbound)
Phase angle at -3hours = 51.5 deg.

RADAR SAR and ISS imaging highlight the science plans for tonight's T7 flyby of Titan. This is the 8th flyby of Titan out of 45 planned for the nominal mission. The 7th flyby, T6, took place on August 22, and yielded plenty of data for CIRS and MAPS, but not much for the other remote sensing instruments. However, during T7, RADAR, ISS, and VIMS make up for lost time.

This flyby is lower than the August flyby, with Cassini coming within 1075 km of the surface of Titan. This is higher than the originally planned 950 kilometers. Many of the 950 km flybys may have to be similarly raised due to higher atmospheric densities at higher altitudes than expected. As you can see in the above plot, Cassini will once again look at the sub-Saturnian hemisphere of Titan on its inbound leg. This hemisphere has been in view of the last 3 flybys, but have no fear, Cassini will return to the anti-Saturnian hemisphere and the Shangri-la region during T8 in late October.

ISS controls the spacecraft for much of the period prior to closest approach. Two large mosaics are planned. The first is a mosaic at about 10 hours out. This should have similar coverage and resolution to the global mosaics taken during Ta and T3, global with a resolution of about 2 km/pixel. The second is a higher resolution mosaic taken from 5 hours out to about 1 hour out. The coverage map for this mosaic should be out soon, but this mosaic would have enough time to build up a large mosaic with similar coverage and resolution to those taken on Ta and Tb. Overall this is shaping up to be one of the better flybys for ISS in some time. Phase angles are similar to those from the past few orbits, higher than those from Ta-Tb-T3. Lots of interesting features at the center of the disk including Bazaruto Facula (with an 80-km wide crater at its center), Quivira with its possible channels and a debris deposit bisecting the feature and flowing into Northeast Aztlan, and Omacatl Macula.

RADAR is back for T7. So far, RADAR has acquired two SAR (synthetic aperature radar) swaths, first on Ta and again on T3. Both swaths covered portions of the northern leading hemisphere. On this encounter, RADAR SAR will acquire a swath over the southern sub-Saturnian hemisphere. I have produced a coverage plot for this swath, though I would ask that it not be reproduced on other sites. The swath starts out in north central Tsegihi, an area of bright terrain, which appears to be similar to Xanadu but slightly darker in albedo. Like Xanadu, Tsegihi is a region of mottled terrain, though with less contrast than Xanadu. Continuing along, RADAR will run into Mezzoramia, a "dinosaur-shaped" dark region that maybe a temporary reservoir of seasonal rainfall run-off from the south polar region. Images of Mezzoramia from July of last year indicated a possible difference in how sharp the southern and eastern boundary is compared to the western and northern boundary. It will be interesting to see if such a difference is detected in the RADAR coverage of the region. The SAR swath continues to as far south as 77 degrees south Latitude, even farther south than Ontario Lacus, a 235-km wide dark feature that maybe a lake. Many of the lake-like features near the south pole appear to concentrated on the leading hemisphere side of the pole, though this could be an emission angle effect (surface contrast improves as you approach the sub-spacecraft point). So RADAR SAR may miss most of the larger "lakes", but smaller features, like those seen on Ta, are possible. T0 images reveal a possible dark feature that maybe similar to Ontario Lacus to the southeast of Mezzoramia, near 70 South, 330 West, so that might be something to look out for. The eastern half of the SAR swath is in a region not seen very well by Cassini ISS (best pixel scale ~ 35 km). This region could be very similar to the area seen by RADAR on Ta, with a lot bland terrain puntuated by the occasional volcanic center.

RADAR also has altimetry and radiometry on this pass. Altimetry will cover the bright-dark southern boundary of Chang-tu at the far eastern end of the RADAR SAR swath. There should be altimetry at the far western end as well, checking for topography associated with Shiwanni Virgae and north-central Tsegihi. Hopefully, the altimetry won't show a slope to the east this time ;-) RADAR Radiometry will look at the thermophysical properties of the northern anti-Saturnian hemisphere, to compare with results from Ta, which looked at the northern sub-Saturnian hemisphere. This data, taken after closest approach, will cover the region that will be seen by RADAR SAR in late October during T8, an east-west swath that will cover central Belet and central Adiri. This region will also be see quite a bit by the remote sensing instruments, like ISS, later in the mission.

Of course, other instruments will gather data during this encounter. UVIS has their second star occultation of Titan's atmosphere, this time using alpha Pegasus (Markab). UVIS will be using the occultation to look for N, N₂, and hydrocarbons at various latitudes. This is a "glancing" occultation since the star will not pass behind the limb of Titan, only the upper atmosphere. The December 2004 occultation of lambda Sco allowed UVIS scientists to detect various hydrocarbons like methane, acetylene, diacetylene, ethane, ethylene, as well as Hydrogen cyanide in Titan's atmosphere as well as measure the abundances of those species. VIMS is prime for almost 4 hours on approach to Titan, starting around 8 hours and 45 minutes before closest approach. This will allow VIMS to create a full-disk mosaic similar, but at lower resolution, to our MONITOR mosaic taken shortly before VIMS' MEDRES observation. VIMS will also take a few snapshots near closest approach northeast of Shiwanni Virgae. CIRS and the Fields-and-Particles instruments will also be active on this encounter. CIRS will be continuing to look for variations in the distribution of hydrocarbon species both temporally and spatially. The MAPS instruments, like MAG and MIMI, will continue to examine the interaction between Titan and Saturn's magnetosphere.

Playback of T7 data takes place during two playback periods. The ISS images of the surface will be returned tomorrow night and Thursday morning and should show up on the JPL raw images page Thursday afternoon, PDT. The rest of the data will be played back starting at around 5:30 am Friday morning, PDT and will continue until around 2 pm PDT. Images from this period, mostly from after Closest approach, should be on the raw images page Friday evening. RADAR SAR data will be played back during this playback period, so don't expect any data from them to show up until at least Monday, and even that is pushing it. Given the weekend and the fact that a number of RADAR team members are in transit from the DPS conference that takes place this week, I wouldn't expect any images from the RADAR team until at least Wednesday. I know that's a long time, but we should have patience with the RADAR team in getting their data assembled.

DPS News and Notes

2005-09-06T09:14:00.000-07:00

The AAS' Division of Planetary Sciences Conferences is taking place as I type in Cambridge, England. No, I am not there. But the Planetary Society's Emily Lakdawalla is and she has a great blog post with some of the results from yesterday's Cassini talks. Among the highlights include Larry Soderblom's confession that the DISR mosaics may have north off by as much as 15 degrees counter-clockwise, which is a major relief for me given my work to try to find the landing site in ISS images. Given their current understanding of "north", I could not find any site that matched orientation of the islands seen in the DISR images. Now with this revelation, there is a solution (easternmost tip of Adiri). Larry also mentioned the planned coverage by RADAR SAR of the landing site in T8. This swath is an east-west pass across central Belet and Adiri. The RADAR team extended the Beam Three path (at the expense of altimetry) to try to cover the landing site, but the signal/noise ratio maybe a bit low, I'm afraid. Hopefully, something good will come out of it and we can start making sense of all our data. FYI, RADAR SAR swaths are composed of five beams (you may have noticed the seams in early RADAR products). Beam three is the center beam and has the best signal to noise ratio. The Principal Investigator of the HASI instrument on Huygens reported that his instrument found a number of inversion layers in the Titan thermosphere. This confirms the INMS result that showed a number of waves in the methane and temperature profiles in the upper atmosphere. Apparently this wave structure continues down to at least 510 km. Now why is this so important... The SSP and the Permittivity Sensor on HASI both detected slight changes in conditions at the surface after landing. The increase in permittivity and changes in the speed of sound and spacecraft tilt maybe related to the vaporization of methane by Huygens as it sat on the surface, but that is just one possibility.

There were a number of results from the instrument teams from onboard Cassini. Many of the major results announced today were related to the rings and Saturn, and rightly so since admittedly they have gotten very little press coverage compared to the satellites so it is good they have their day in the sun. But this is a blog about the satellites, so who cares about those results ;-) Most of the Enceladus results were announced earlier at a press conference but some instrument teams did clarify them. VIMS last week announced they had found crystalline ice (absorption band at 1.65 microns) and simple organics (absorption band at 3.44 microns). During his talk, Bob Brown mentioned that the aborption band is attributed to a C-H stretch. In other words, it is some kind of organic compound, but VIMS can't tell what it is with just this one absorption band. Brown also announced that VIMS had not found any ammonia on Enceladus, shutting the door on ammonia-water volcanism. I'm not sure I agree with him there, but we may want to look at models that don't include ammonia. This also fails to explain how INMS saw N₂. The CIRS principal investigator, Mike Flasar reported on results from Enceladus. In addition to the hotspot in the south polar region, CIRS found a relatively low thermal inertia, indicating that Enceladus is covered in unconsolidated material. Perhaps due to infalling E-ring material.

Finally, the RADAR team presented their results from T3. The most interesting features in that swath were the numerous linear to sublinear dark streaks, nicknamed cat scratches. These features have been interpreted as linear or longitudinal dunes, similar to those found in Saudi Arabia and Australia (near "Lake" Eyre). However, the RADAR team has been comparing the scratches to icy dunes in Antartica, which are visible in RADAR images of the continent, but not so much from the ground. The dunes take the form of changes in grain size rather than topographic features that one could see from the ground. Such an interpretation would jive with ISS' inability to resolve the scratches if both the dunes and the material that fills in between them are dark at 938 nanometers.

RADAR also released an image yesterday showing these dunes and a couple of drainage channels west of the "Circus Maximus" impact basin.

New Janus Image: The Two Faces of Janus

2005-09-06T09:03:00.000-07:00

CICLOPS has released this view of Saturn's moon Janus taken on August 2. This view shows only a slim crescent of Janus lit by sunlight, highlighting a couple of craters near the terminator. On the left side, however, Janus is dimly lit by Saturn, to the left of this image. Several large impact craters are visible in the Saturn-shine.

Janus is a small, irregular satellite of Saturn, only 181 km across. Cassini's closest encounter with Janus won't come until the very last day of the nominal mission, June 30, 2008, when Cassini is scheduled to come within 45,000 km of the surface of this satellite. Cassini flew within 50,000 km of another small satellite of Saturn, Pandora, yesterday for Cassini's closest encounter with that satellite during the nominal mission.

Pandora Rev14 Non-Targeted Encounter

2005-09-05T18:33:00.000-07:00

Today, Cassini will come within 52,000 km of the surface on one of Saturn's small, inner moons, Pandora. Pandora acts as one of the shephards of the thin F ring, orbit just outside of the ring. Pandora is a small, irregular, with a diameter of 114x82x62 km. Voyager views of Pandora's surface showed a ancient, heavily cratered world, but Cassini views, like the one above, suggest that, though heavily crater, small-scale topography may be subdued, perhaps due to F ring material mantling the surface.

This encounter with Pandora, while not a targeted flyby, will provide our best views of the satellite thus far and at 52,000 km, this will be the closest Cassini will come to this satellite. The best possible images from Cassini at closest approach would have a resolution of 300 m/pixel over the satellite's trailing hemisphere (assuming that it rotates synchronously which I believe it does).

Images and other data from this non-targeted encounter should be returned tonight or tomorrow.

More New Titan Names

2005-09-02T10:51:00.000-07:00

The IAU's Working Group for Planetary System Nomenclature (WGPSN) has approved 12 additional names for features on the surface of Titan. These include names for various albedo features on the surface of Titan, including the northern H region. Two additional types of features are included in this round of names, like Arcus (arc-shaped features) and large ringed features, ring-shaped albedo features that are currently thought to be craters. Some of the highlights in this round of naming include:

The feature previously nicknamed "Pelopennesos" is now known as Oahu Facula. This feature is similar to the other bright "islands" in Shangri-la, but appears to be connected by a narrow isthmus to Dilmun.
The bright, Arc-shaped bright feature, associated with a very bright spot at 5-microns, has been named Hotei Arcus.
The feature previously nicknamed "Manhattan" (because it is shaped like a big apple) is now known as Texel Facula. This feature is located at the far eastern end of Antilla Faculae in western Shangri-la.
The VIMS "snail", interpreted by the VIMS team as a possible volcano (or cat feces, depending on who you ask), is now Tortola Facula.
Several ring-shaped features have been named, including two in eastern Shangri-la near its boundary with Xanadu (Guabonito and Veles) and in north-central Tsegihi (Nath).
The northern H region is now named Fensal. A possible name now for the H region as a whole could then be "Fensal-Aztlan"

The USGS site now has a map with names.

Enceladus Animation

2005-09-01T10:39:00.000-07:00

The Photojournal has an animation with a wrap-up of the results from the July flyby, showing both the effects of Enceladus on Saturn's magnetic field as well as showing the great images and fantastic mosaic produced during the encounter. Definitely worth checking out.

Arcus on Titan

2005-09-01T10:33:00.000-07:00

The IAU's Working Group for Planetary System Nomenclature (WGPSN) has approved the feature type, Arcus. This term will be used for arc-shaped albedo (possibly topographic as well) features. This feature type would applicable to such features as the "smile", found to be very bright at 5 microns by VIMS.

No word yet on additional names for Titan and this "arcus".

New Tethys Image: Tethys in the Dark

2005-09-01T10:23:00.000-07:00

CICLOPS has released this processed view of Tethys taken on August 3, when Cassini was 842,000 km from the satellite. Only a thin crescent was visible of Tethys at the time this image was taken, when the phase angle was 144 degrees. Images like these can be used to study the photometric properties of the surface material on Tethys, particularly with how backward scattering it is. Two good sized craters can be seen along the terminator, or the dividing "line" between night and day. The one at about the 3:30 position is Penelope. The smaller crater near 5:30 is Antinous. While it hasn't been stretched to make it visible, much of the left part of Tethys' disk viewed here is lit dimly by Saturn-shine. This technique, however, requires longer exposure times than those used here to be useful for geologic analysis.

This image has a resolution of 5 km/pixel.

Enceladus' Tiger Stripes

2005-08-30T15:10:00.000-07:00

A lot of big news today about Enceladus as all the major instruments on Cassini reported their results. Most of the results revolve around the four prominent fractures in the south polar region known collectively as the "tiger stripes". These "stripes" are actually tectonic fractures, 140-170 km long and a couple of hundred meters deep. In the IR3 filter on the Cassini Narrow Angle Camera, sensitive to infrared light around 920 nanometers in wavelength, the fractures are surrounded by dark material lying between 2-5 km on either side of the fractures. When combined with the green and UV3 filters for stretched color images, the stripes appear blue to blue-green. On one of the stripes, a darkish spot, 3 km in diameter can be seen.

To sum up what we have learned today from VIMS, we know that the coarse-grained ice along the edges of the tiger stripes consists of crystalline ice (based on an absorption at 1.65 microns, not seen elsewhere on the satellite), which only forms at temperatures above 110 K. These crystals will degrade over time after cooling below 110 K thanks to the radiation environment, in a few decades up to a thousand years. This is what led to the VIMS teams claim that the fractures are young, less than 1000 years old, maybe even 10 years or younger. However, they are basing this on compositional evidence of the crystallinity of the ice. The crystalline ice could be ice brought up to the surface after the most recent eruption, not necessarily signalling that the fractures themselves are 10-1000 years old (though we couldn't rule it out, no craters larger than 400 meters or so have been found south of 70 degrees south latitude). VIMS also found simple organics along the fractures with a similar distribution of crystalline ice, based on an absorption at 3.44 microns.

So how did that material, crystalline ice which requires relatively warm temperatures (> 110 K), which appear to have coarse grains based on other VIMS measurements and ISS color spectra, and simple organics get there? INMS, as mentioned below, measured mostly water vapor above the south pole, along with N₂, CO₂, Hydrogen, and 1-2% CH₄ and C₂H₂. So one could envision the plume scenario powered by a water-ammonia diapir almost directly below the south pole, where water vapor escapes from fresh fractures in the crust. The material with the lowest energy will be deposited just adjacent to the fractures and the material with higher energies will form a plume and then a transient, patchy atmosphere. So far, no nitrogen-bearing compounds in spectra of Enceladus and only hints of CO₂have been observed. But still, depsosition from a plume, rather than sublimation of fine-grained, amorphous ice seems reasonable. It is possible, though, that surface ices bordering the warmer fractures were transformed into crystalline, coarse-grained ice from the heat coming from the fractures. However, the simple organics, found no where else on the satellite (in fact the spectra of the rest of the satellite mirrors laboratory-quality water ice), would still need to be explained.

Even More Enceladus from the BBC and New Scientist

2005-08-30T12:24:00.000-07:00

New Scientist and BBC News both have fantastic articles on the press conference today in London on Enceladus. Both cover similar results from the two press releases, but both do mention that VIMS found simple organic compounds along the tiger stripes (shown above) in addition to crystalline ices. This may confirm the marginal detection of methane in the INMS mass spectra. No word yet what the simple organics are. I'm trying to find out as I type this. The New Scientist articles does go into speculation that the boulders seen by ISS at very high resolution may be lava bombs, but such a mechanism may not be necessary given the intense tectonic reworking of the region. Torrence Johnson is quoted as saying, "They are awfully large, but Enceladus' gravity is weak, so it doesn't take much to lift stuff off the surface".

Major Eruption at Enceladus?

2005-08-30T11:19:00.000-07:00

In the first half of 2004, as Cassini approach Saturn prior to SOI, UVIS detected a dramatic increase in the amount of atomic oxygen in the Saturnian system, centered near the orbit of Enceladus. At the time of the announcement, the increase in mass in the region, roughly equivalent to the total mass of the E ring, was attributed to the collision of two km-sized particles in the E ring. However, the UVIS principle investigator, Larry Esposito, stated at the CHARM telecon today that "the water vapor escaping from Enceladus is adequate to supply the atomic oxygen in the Saturn system detected by UVIS, and to re-supply Saturn's E ring." So, what do we make of these two pieces of data, the likelihood that Enceladus supplies the atomic oxygen in the Saturn system and this dramatic increase in atomic oxygen last year. The obvious mechanism would be a major eruption on Enceladus. During this eruption, tremendous amounts of dust and water vapor was pumped into the E ring and the Saturn system. Certainly a very interesting idea that hopefully the UVIS team is examining.

"Enceladus Eruptions" CHARM presentation

2005-08-30T10:41:00.000-07:00

Today's CHARM talk covered the UVIS results at Enceladus from the flyby last month. I've linked to the PDF file with the slides from the talk above. This talk fit nicely with the press briefing today since it perfectly covered many of the discoveries announced at the talk plus providing more in-depth analysis of the data as well as...more graphs. UVIS detected an atmosphere on ingress of the gamma Orionis occultation in July but failed to detect an atmosphere during the occultation in February. The path of the occultation allowed for measurements at a far southern latitude on ingress, allowing UVIS to measure the patchy atmosphere measured by MAG and INMS. UVIS was able to detect the atmosphere starting at an altitude of 155 km above the surface of Enceladus using the High Speed Photometer (HSP) on UVIS. Compositionally, UVIS found that the atmosphere/plume was made primarily of water vapor with no detection of CO (thus placing an upper limit on CO at 2x10¹⁴ cm^-2. This is important because INMS detected a species at mass 28 which can either be CO or N₂. N₂ could be a disassociative product of ammonia in Enceladus' patchy, slushy interior.

In addition to the UVIS data, the talk, by Larry Esposito the UVIS Principle Investigator, also has data from INMS, with a plot of their data from below 500 km. The plot shows a high number of counts from H2O and less amounts from a species at mass 28 as well as hydrogen and maybe methane. The detection at mass 44 is a mix of background noise and CO₂. The presentation also has plot from the simulation the CDA team ran to show that their data was consistent with a spread out source near the south pole.

Esposito concludes by stating that the composition of the atmosphere is mostly water vapor with a near surface abundance of 1.5 x 10¹⁶ cm^-2 with an upper limit on CO at 2% the water vapor density. The atmosphere is not global and has only been found near the south pole. Finally, and here is the kicker as I will go into with more detail later today, "The water vapor escaping from Enceladus is adequate to supply the atomic oxygen in the Saturn system detected by UVIS, and to re-supply Saturn's E ring."

Update 12:45 pm: The detection at mass 44 is a mix of background noise and CO2. Not sure what the mix is, but is less than the detection at mass 28...

More on Today's Enceladus News

2005-08-30T09:44:00.000-07:00

As mentioned in the last post, the ISS, CIRS, INMS, and CDA teams worked together to produce a plot showing the locations of peaks in temperature, water vapor, and dust on a polar projection map of the surface of Encleladus. At first glance, the peaks for INMS and CDA would seem to suggest that the circumpolar ring of folded, tectonic terrain may be the source of the vapor and dust. However, neither peak is located within the region of warm ice seen by CIRS, an area that would be more likely to see significant activity. Numerical simulations by the CDA team, combining the timings of the CDA and INMS peaks, suggest that both the vapor and the dust are connected, have the same source, and are distributed across a small region on the surface near the south pole. The source is not impact-generated dust which would be uniform across the surface, as originally thought.

So what does this say about how the vapor and dust form? Three possible scenarios were presented at the press conference. The first scenario sugggests that sublimation of ice within warm, 140 Kelvin fractures, could produce the vapor. This would fit with the lack of a visible plume by ISS but may not fit with the dust detections. The dust could possibly be produced by condensing vapor, but this may not be supported by the CDA data. The second scenario suggests that vapor and dust are generated by a plume that eruptions along the tiger stripe fractures. This would easily allow both vapor and dust to be ejected to the altitudes seen by INMS and CDA but thus far, no plume has been observed by ISS. The third scenario suggests that vapor and dust could be produced by sublimation along cryolava flow fronts. While some of the terrain between the tiger stripes looks like a lava flow, the distribution of crystalline ice seen by VIMS and the blue-green course-grained ice seen by ISS have been observed along the fractures, not within the flows, so it seems that this scenario may not fit the current conditions. My only complaint about the graphic is that it assumes that the interior is made of only water, not water mixed with ammonia, which would lower the melting point of water. I don't see why you can't have the plume scenario with a sub-surface layer of water mixed with ammonia (just to answer Jerry's comment about the required temperatures).

So which scenario are scientists leaning toward? Considering current conditions and what we have observed geologically, I would definitely lean toward the second scenario for a few reasons. While we have not observed a plume, there are some indications that activity at Enceladus may be quite variable. UVIS detected a large increase in the amount of oxygen in the E ring early last year. Considering that the primary source of the E ring is now found to be the south polar vents, it seems reasonable that such a mass increase could have been due to a major eruption on Enceladus. Such variability with time may be difficult to achieve with the first scenario. Plus, one has to consider how you get dust particles along with the vapor in a purely sublimation scenario. You can do it, but I find it hard to believe you can do it with this much dust. The third scenario could partially fit, the terrain between the tiger stripes does look an awful lot like a lava flow. However, the distribution of course-grained ice, the sublimation problem mentioned in the first scenario, and the lack of ammonia detected on the surface seems to suggest that the cyroflow sublimation model is not the best fit. So I would consider the second model, the plume model, as the best fit to the data.

The ISS team also released preliminary tectonic maps showing the distribution of longitudinal and latitudinal fractures on the surface. These maps show that many of the fractures on Enceladus follow longitude and latitude lines, perhaps caused by the changing shape of Enceladus as the tidal stresses on Enceladus wax and wane. In addition these maps outline a wavy, circumpolar ring of fractures at around 55 degrees South latitude, marked by Y-shaped discontinuities that lead into fracture systems that lie along lines of longitude. Such fractures could be caused by "hoop stresses", formed during periods when the equator expanded, perhaps as Enceladus was sped up. Unmarked versions of these maps of the north and south polar region show the marked difference between the two polar terrains. The north polar region is heavily cratered and is the oldest region on the surface of Enceladus. The south polar region is very young with very few craters south of 55 degrees south, and none (larger than 200 meters) south of 70 degrees south. Note the hooks at the end of the tiger stripe fractures.

More Enceladus to come.

Tiger Stripes on Enceladus found to very young and active

2005-08-30T09:00:00.000-07:00

At a press conference in the UK at the Cassini PSG (Project Science Group) meeting, additional details from the July flyby of Enceladus were revealed. The briefing focused on the cryovolcanic activity observed in the south polar region observed by a number of Cassini's instruments, including ISS, VIMS, CIRS, INMS, UVIS, and CDA. There is a lot of ground to cover on this and I will be posting several times today on this story.

First, INMS and CDA observed asymmetries in their data that have been plotted on a graph as well as shown on a polar projection map of Enceladus with the ground-track and the locations of the CDA and INMS peaks, and the CIRS hotspot, indicated. Previously, CDA reported that their data was consistent with impact-generated dust, not from endogenic activity. If you look at the graph, it is pretty close to a bell-shape curve, which is what you would see in an impact-generated dust scenario. However, the curve is shifted in time from closest approach, with the peak occuring 70 seconds before C/A. In the impact-generated dust scenario, the peak would be right at closest approach, so this shift would not be consistent with that scenario, but with one where dust is ejected up to a certain height from a volcanic vent. So it now appears that the south polar region of Enceladus is the source of the very small particles in the south polar region. UVIS data from two star occultations in February and July also seem to suggest that the "atmosphere" produced by the venting of water vapor and micron-sized dust is not global and localized to the south polar region.

VIMS was also at the press conference, showing a view of the surface of Enceladus taken by their instrument. This image shows the distribution of crystalline ice on the surface, which under Enceladus conditions quickly degrades to amorphous ice. VIMS found that there was quite a bit of crystalline ice in the area surrounding each fracture collectively known as the tiger stripes (because of their appearance and the way they standout in the normally very bright south polar region). Considering the conditions at Enceladus, crystalline ice is expected to convert to amorphous ice over a period of several decades so geologic activity along the stripes must have occured between 10 and 1000 years ago (though more recent episodes are certainly possible, and likely, as I will discuss in a post later today).

In my next post, I will discuss the ISS releases as well as the possible models for activity.

New Rhea Image: Tirawa at Twilight

2005-08-30T08:00:00.000-07:00

CICLOPS released this processed view of Saturn's moon Rhea today. This image was taken on August 13 from a distance of 2 million kilometers and has a resolution of 12 km/pixel (though the processed view has been magnified by two times to aid visibility). This view of Rhea is centered just west of a prominent ray crater on the surface of Rhea. Near the terminator, to the northwest, is a 360-km wide impact basin known as Tirawa. Based on Voyager measurements, Tirawa is 5 km deep.

Off-topic: Hurricane Katrina

2005-08-29T13:59:00.000-07:00

A bit off topic but I have just been mezmorized by the coverage today of this hurricane. Thankfully, New Orleans was spared the worst, but still there is going to be a lot of cleanup related to this storm, particularly in eastern New Orleans, Biloxi, and Gulfport. My prayers go out to those in that area and hopefully all those in the effected areas will be safe. Now for some links:

Eye of the Storm blog. This is a blog created by a couple of reporters for a local paper in Biloxi, Mississippi, covering their coverage of the storm and its aftermath. An interesting recent post covers how one of the reporters ran outside and "mooned" the hurricane. His mooning made it on the wires because a Reuters' photographer was taking shelter in their newsroom.
Dr. Jeff Masters' Tropical Weather Blog. One of the major blogs on wunderground.com. Great info.
Steve Gregory's Tropical Weather Blog. Another great blog on wunderground.com. A little bit short on analysis but he does post great pics, like the one above.
Weather Underground's Tropical Weather page. Definitely a better resource than the Weather Channel site.
National Hurricane Center. Well, duh.

Update: 09/02/2005 11:40 am: Obviously, since I wrote this post, the situation in New Orleans has deteriorated. Those in Katrina's desperately need your help. I urge those reading this blog to donate to the American Red Cross. You can easily donate using Yahoo's Red Cross page.

New Mimas Image: First Quarter Mimas

2005-08-26T09:30:00.000-07:00

CICLOPS today released this view of Mimas taken on July 18. In this image, Mimas was at half-phase, allowing Cassini scientists to view craters along the terminator even from this distance. In the background is a portion of Saturn's northern hemisphere, shaded by the shadows of its ring system. This image was taken from a distance of 1.6 million kilometers from Mimas and has a scale of 10 km/pixel.

T6 Released Images

2005-08-25T11:00:00.000-07:00

CICLOPS has released two processed views of Titan's surface from images taken during Monday's T6 flyby. Not many useful surface images were taken during this encounter, but the above wide-angle image does show the surface as it looked on Monday. Shortly before, Cassini took at visible color view of Titan, showing Titan to be nothing but a bland ball of light orange.

The surface image shows the "H" region of Titan. The southern branch is now named Aztlan, after the Aztec homeland. Aztlan also includes the large, roughly circular region to the east with a bright "island" named Elba Facula in the middle. North of Aztlan is a couple of bright islands collectively known as Quivira. Finally, norh of Quivira, is a bright "island" with a dark spot in the middle (known to be an 80-km wide crater) known as Bazaruto Facula.

New Rhea Image: Above Rhea's South Pole

2005-08-25T10:03:00.000-07:00

This global view of Rhea, taken on July 14, was released today by CICLOPS. This image, with a resolution of 2 km/pixel, shows the south polar region of Rhea, an area not seen at decent resolution before this non-targeted encounter. Very few non-impact related features are seen in this view, indicating that Rhea has a very ancient surface. A fairly young crater with bright ejecta extending for hundreds of kilometers can be seen at upper right. This impact crater has been seen on numerous occasions, and higher resolution images show that the crater has an irregular margin, perhaps indicating that while young, the impact has undergone alteration since formation. The fact that nearly all craters on Rhea show irregular outlines may also be an indication that something about Rhea's surface leads to the formation of irregular shaped craters.

New Tethys Image: With the Band

2005-08-24T10:37:00.000-07:00

CICLOPS has released this view of Tethys taken on July 10 from a distance of 1.8 million kilometers (for a resolution of 11 km/pixel). This image shows Odysseus crater near the terminator at upper left as well as the crater Melanthus at lower left. One striking feature noted numerous times here is the dark band on Tethys that runs from west to east from southwestern Odysseus basin to Ithaca Chasma. The origin of this feature is currently unknown. Overall, the albedo of this region of Tethys looks stratified, with brighter material in the southern hemisphere, the dark stripe, and then intermediate albedo material in the north, though this could just be a lighting effect.

New Pandora Image: Pandora Glides Along

2005-08-23T10:35:00.000-07:00

This image, released today, shows Pandora transiting Saturn as seen from Cassini. In this view, both Saturn and Pandora are at moderate phase angles (you can even see the night side of Pandora against the dawn sky of Saturn.

This image was taken on July 16 from a distance of 1.3 million km. The resolution for this image is 6 km/pixel (for Pandora).

New Cassini Image: Supreme Beauty

2005-08-22T10:33:00.000-07:00

CICLOPS released view of Tethys in front of a beautiful shot of Saturn. Nice catch!

T6 Coverage Plot

2005-08-19T09:31:00.000-07:00

CICLOPS has released a coverage plot showing the regions that will be imaged by ISS during Monday's flyby of Titan. This is the same region that was covered during the last two Titan flybys in March and April. Since ISS doesn't have prime coverage on this flyby, there are no complex mosaics for this encounter because higher resolution images would be smeared by spacecraft motion during CIRS slews. ISS will be taking advantage of that by taking flat-field images (images that show no discernable surface features, but clearly show camera artifacts). The best images taken by Cassini during T6 will be of a newly named feature called Bazaruto Facula, a bright region thought to consist of icy ejecta from an 80-km crater at the center of the feature. The southernmost portions of the highest resolution images will show the bright region known as Quivira. The areas of larger coverage (2-5 km/pixel), cover much of the "H" (southern portion of the H now known as Aztlan) and northern Tsegihi.

See the T6 post below for more information on this encounter.

Titan-6 Flyby Info

2005-08-18T13:29:00.000-07:00

View of Titan from Cassini 2 hours prior to closest approach (sub-spacecraft point=4.09N, 30.39W). The plot was generated in GISS' Titan 24 software. The map is derived from ISS map released in March (ask for full version used here, just adds blank space north of 34N).

On Monday, August 22, Cassini will preform its seventh close encounter with Saturn's largest moon Titan. Cassini has not flown within 400,000 km of Titan since April 15, when Cassini flew within 1025 km of Titan's surface. This encounter will be a little farther away from Titan, with Cassini coming within 3670 km of the surface. This encounter is an all-CIRS flyby, with the Composite InfraRed Spectrometer instrument controling the spacecraft through the entire encounter period. The goals for the CIRS instrument include:

Surface temperature mapping
Vertical aerosol mapping through limb integrations
Atmospheric temperature profiles at different latitudes
Latitude and altitude compositional variation mapping in the near- to mid-infrared using both nadir and limb mapping
High-resolution integration over the south pole near closest approach

With so many different types of integrations, CIRS will be able to show off its versatility.

Another major highlight is the magnetospheric studies. During the encounter, the magnetometer and other fields-and-particles instruments, like the RPWS, will study the exotic dayside wake/tail region of Saturn's magnetosphere and how it interacts with Titan.

With no prime coverage, ISS will be strickly in ride-along mode. Therefore, unlike the previous encounter of Titan, there will be no complex mosaics on Titan to ooo and ahh over. The ride alongs will show the region above, in the Quivira-Aztlan region. At the center of this view is an 80-km crater first seen by RADAR in February. It is surrounded by an area of bright material known as Bazaruto Facula. ISS will also acquire numerous flat-field images during CIRS slews to improve calibration.

A few facts about this flyby:

Occurs on August 22 at 2:16am PDT
Closest Approach Distance = 3669 km
Relative speed WRT Titan = 6.1 km/sec
Closest Approach Lat and lon = 58.5S, 102.7W
Southern hemisphere pass
Outbound flyby (sunlit inbound)
Phase angle at T-2hours = 48.3 deg.

Data playback begins at 10:05 pm PDT on August 22 and continues until 07:05 am PDT the next day. Based on prior experience, it appears that images start showing up on the JPL raw images page over an hour period about 10 hours after the start of the playback. This would mean that images will show up on the raw images page at around 8 am PDT August 23.

Rev13 Hyperion Images

2005-08-18T09:54:00.000-07:00

New images of Hyperion, taken over the last couple of days, are now posted on the JPL Raw images page. These images were taken from four times the distance of the images taken in June, but are not saturated like those images, allowing for better color information to be derived. Of course, this is but a taste of what is to come, as next month, on September 25, Cassini will fly within 500 km of the surface of Hyperion, allowing for the highest resolution coverage of Hyperion for the Cassini nominal mission. Images taken in June revealed a segregation of bright and dark material, with dark material occupying crater floors. They also revealed a fascinating array of crater morphologies, which maybe related to the effects of Titan on Hyperion's ability to re-accrete material from impacts on its surface. A rather "normal" looking simple crater can be seen in the image above, however, near the lower left.

Many of the images taken during orbit 13 have looked at areas made famous by Voyager. This region is dominated by a tall scarp known as Bond-Lassell Dorsum, which maybe the remnants of a large impact on Hyperion.

UPDATE: 08/18/2005 2:15 pm: Emily Lakdawalla has additional information on these images as well as an animated gif showing the sequence of images taken during this distant encounter on her Planetary Society Blog.

New Epimetheus Image: Looking Down on Epimetheus

2005-08-18T09:15:00.000-07:00

CICLOPS has released this view of Epimetheus taken on July 14, shortly after the Enceladus flyby. This images was taken from a distance of 87,000 km and has a resolution of 520 m/pixel, making this one of the highest resolution views of this small world. Epimetheus is covered in craters with no signs of internal activity. The two named features on Epimetheus, Pollux and Hilairea can be seen in this view at left and toward the lower left, respectively. Hilairea has several craters on its floor, indicating that it is a relatively old feature on the surface.

This view shows a region on Epimetheus slightly north and east of the area seen in March.

New Rhea Image: Polar View

2005-08-17T10:26:00.000-07:00

CICLOPS has released this view of Rhea's south polar region. Unlike Enceladus' polar region, Rhea's is heavily cratered. The largest crater in this view is an 115x90 km wide impact crater toward the upper right. There are very few features in this scene that suggest an endogenic origin. An odd gash can be seen at left.

This image was taken on July 14 and has a resolution of 1 km/pixel.

Titan Features Receive Provisional Names

2005-08-16T11:30:00.000-07:00

Goodbye "Great Britain", hello Shikoku Facula. After more than a year of using nicknames for features on the surface of Titan, features on the surface are now recieving official names. For almost 6 months, the only features that had provisional names were Xanadu, the bright region in the equatorial leading hemisphere, and Ganesa Macula, a possible pancake-dome volcano found by RADAR last October. Now a number of features seen by ISS over the last year have been given provisional names by the IAU. The process began in May when features were selected as important enough to receive names and a proposal was submitted to the IAU, the body that governs astronomical nomenclature. The process was hampered by the same problems that plague scientists, without the support of detailed compositional and topographic information on many of the features that need names, we are left with just albedo markings, which can often be ambiguous at best. So classifying features under many of the existing nomenclature categories was difficult. Such ambiguities led to the creation of several new terrain type, such as virga, which pertains to a streak or stripe of color.

Among the highlights of the new feature names include:

Shangri-la, the dark region west of Xanadu
Shikoku Facula, the "island" shaped like Great Britain in central Shangri-la
Mindango Facula, the "island" shaped like Ireland in central Shangri-la
Adiri, a bright region between Shangri-la and Belet, Huygens landed on the western tip of Adiri, the T8 SAR swath will cover the central portion of Adiri
Belet, dark region west of Adiri, the T8 SAR swath will cover the central portion of this dark region
Ontario Lacus, the "lake" from June
Mezzoramia, jrehling's drainage region
Omacatl Macula, dark streak north of the "H"

The "H" feature itself doesn't appear to have a name though the southern portion appears to be named Aztlan. The large bright feature in the east central portion of the H are known as Quivira. The angular island, highlighted in T5, is now known as Coats Facula.

New Titan Image: Dawn at the Huygens Site

2005-08-16T10:18:00.000-07:00

CICLOPS has posted this view of Titan taken last month from a distance of 1.3 million km. This view shows the boundary between Xanadu and Shangri-la. This region was seen a number of times during the Ta, Tb, and T3 encounters and will next be seen upclose during the T8 encounter in October. However, this region has not been seen at this phase angle, providing an opportunity to examine the terrain in this region and its photometric properties. At the time this image was taken, the sun was rising over the Huygens landing site, off the Adiri "coast". The lake-like feature prominently features in images taken in June, Ontario Lacus, can be seen near the bottom, along with a few clouds.

Raw Images of the Day

2005-08-15T12:26:00.000-07:00

Time now for "Raw images of the day":

Space.com article on Enceladus Activity

2005-08-15T09:54:00.000-07:00

Space.com now has an article up on their website covering the recent discovery of active volcanism on Enceladus. Not a bad article, nothing new, but it is nice to see space.com cover something other than the Space Shuttle and catch up with the rest of the news.

New Epimetheus Image: Epimetheus on the Outside

2005-08-11T13:45:00.000-07:00

CICLOPS released yesterday this view of Epimetheus taken from a distance of 1.8 million km on June 30. In this image, you can't seem much detail on Epimetheus from this distance but faint features within the outer A ring and the F ring are clearly visible.

Icarus (September 2005)

2005-08-11T11:47:00.000-07:00

The index for the September issue of Icarus is now online. Icarus is the journal for the American Astronomical Society's Division of Planetary Science. A number of outer satellite papers are in this issue:

Thermal response of Iapetus to an eclipse by Saturn's rings by G. Neugebauer, K. Matthews, P.D. Nicholson, B.T. Soifer, I. Gatley and S.V.W. Beckwith
The Zamama–Thor region of Io: Insights from a synthesis of mapping, topography, and Galileo spacecraft data by David A. Williams, Laszlo P. Keszthelyi, Paul M. Schenk, Moses P. Milazzo, Rosaly M.C. Lopes, Julie A. Rathbun and Ronald Greeley
Maps of Titan's surface from 1 to 2.5 μm by Athena Coustenis, Mathieu Hirtzig, Eric Gendron, Pierre Drossart, Olivier Lai, Michel Combes and Alberto Negrão
Photochemical processes on Titan: Irradiation of mixtures of gases that simulate Titan's atmosphere by Buu N. Tran, Jeffrey C. Joseph, Michael Force, Robert G. Briggs, Veronique Vuitton and James P. Ferris
Condensed species in Titan's atmosphere: Identification of crystalline propionitrile (C₂H₅CN, CH₃CH₂CN) based on laboratory infrared data by R.K. Khanna

The paper by Williams et al. is a good one. It gives a great description of the 2001 eruption at Thor.

Naming Categories on Titan

2005-08-10T11:10:00.000-07:00

The IAU has approved several changes to the nomenclature of Titan. No names are available (yet), but several changes are encouraging. First, the faculas will be named after islands on Earth (not politically independent). Faculae (groups of bright features) will be named after archipelagoes on Earth. Secondly, a new category has been approved, Flumina. These are channels on Titan that MAY carry liquid. They will be named after mythical or imaginary rivers.

The "categories" page was last updated July 5 so this kinda of old news but this is the first I have seen some of these changes on the web.

Raw Images of the Day

2005-08-10T09:26:00.000-07:00

It's time now for Raw images of the Day:

Mimas map

2005-08-09T11:14:00.000-07:00

Steve Albers has a new version of his Mimas map on his website. The map includes data from Voyager and Cassini, including last week's encounter. Certainly a lot better than the maps available else where on the web. The map includes improved coverage over Herschel as well as in the anti-Saturnian hemisphere.

Also, don't forget to check out the improved Enceladus map, that now includes data from last month's flyby.

Enceladus, plumes, and the CDA

2005-08-09T09:39:00.000-07:00

Bruce Moomaw has a pretty length post over at the Unmanned Spaceflight.com forum covering some confusion regarding the Cosmic Dust Analyzer (CDA) results from the Enceladus flyby last month. The confusion results from whether the particles seen by the CDA instrument were in fact from impact-generated dust, or from a south polar plume. Early analysis suggested that the particles came from impact-generated dust rather than the south polar "plume" since the dust appeared to be uniform over the surface while the atmosphere/plume is not. Emily Lakdawalla, from the Planetary Society, posted an article a week or so ago describing the results, using information from the press release and an interview with Linda Spilker, the Cassini Deputy Project Scientist. In the article, Lakdawalla quoted Spilker as saying that the dust seen by the CDA instrument (the dust near Enceladus and the E-ring) were different from the water vapor seen by UVIS, INMS, and MAG, and that the south polar vents were not the source of the E-ring. However, as Bruce mentioned in a comment here, if the E-ring was generated solely by impacts on Enceladus, wouldn't other moons like Mimas have the same sort of impact-generated ring co-orbiting with the satellite.. So Bruce did a little digging and talked with Spilker. Turns out that Lakdawalla quoted her incorrectly. The difference between the CDA dust and the atmosphere seen by UVIS et al. is that the CDA saw water particles and UVIS et al. saw water vapor, nothing more.

In addition, Bruce dug up a new tidbit. Previously, the CDA team has been reporting that the dust was uniform across the surface (leading to the conclusion that the particles didn't have a localized source). Even if the particles were formed by condensing water vapor from the vent, there would be some sort of asymmetry in the CDA data biased to the south polar region. Turns out that the CDA may have seen an asymmetry in the amount of dust with respect to location over Enceladus. This is a very intriguing development and may indicate that the particles near Enceladus and perhaps the E-ring itself were formed from condensing particles from vents in the south polar region.

Raw Images of the Week

2005-08-08T16:50:00.000-07:00

Quite news day today, Cassini-wise. So here are some raw images:

New Mimas Image: A World of Hurt

2005-08-05T10:47:00.000-07:00

CICLOPS has released this mosaic of Mimas, consisting of three clear filter images taken near closest approach to Mimas. This mosaic is centered near 18.87 North, 238.73 West and has a resolution of 374 m/pixel. This mosaic represents the highest resolution images ever taken of Mimas.

Two prominent features types become apparent in this view. The first are craters. They are everywhere. Clearly, unlike Enceladus, Mimas has had very little internal activity in its history. The surface is so cratered, new craters can only overprint older craters. The craters do show a wide range of morphology due to various states of degradation. While some show signs of internal deformation, or viscous relaxation, which is the dominant form of crater degradation on Enceladus (along with tectonic fracturing), most are degraded by mass wasting. This causes the crater walls to slump down on to the crater floors. This can be seen in most craters larger than 15 km across. The walls on a number of craters are quite tall, up to 6 km in height.

The second prominent feature type are grooves. These features, some over a kilometer deep and 100 km long, maybe caused by the seismic shaking produced by large impacts, like Herschel.

The two largest craters in this view are the 46-km wide Morgan, just above and to the left of center, and the 52-km wide Arthur, near the limb at lower right.

New Mimas Image: Mimas against the Rings

2005-08-05T10:46:00.000-07:00

This amazing shot of Mimas was taken during a ride-along with the CIRS instrument. Here you can see a high-resolution image of Mimas with the outer A ring in the background. This image has a resolution of 400 m/pixel and was taken from a distance of 68,000 km.

New Mimas Movie: Flying Over Mimas

2005-08-05T10:45:00.000-07:00

CICLOPS has also released a movie showing Mimas as it rotates under Cassini. The movie starts out over Herschel crater and ends up over the highest resolution regions near Morgan crater.

Neat stuf'.

New Mimas Image: Mimas showing False Colors

2005-08-05T10:44:00.000-07:00

CICLOPS has released these two processed views of Herschel crater on Mimas. These views were taken from a distance of 228,000 km and have a resolution of 1.4 km/pixel. The view on the left is a clear filter image showing the prominent impact crater Herschel. The appearance of this crater has given Mimas the nickname "The Death Star Moon" (and if I see any more articles or forum thread titles starting with "That's no moon...", so help me...). The clear filter view shows numerous landslides within Herschel, including one on its eastern side, where a part of the crater wall has slid down on to the floor, leaving behind an alcove.

The view on the right is a color ratio image using data from the same time period as the clear filter image on the left. The brightness is the clear filter image while the color comes from a ratio of IR3 - UV3 divided by GRN. We can that there is a color difference between the area near Herschel and the rest of the satellite. This shows up in the clear filter image as a area of brighter terrain surrounded by slightly dark material. This color difference may be due to ejecta from Herschel. But the uneven distribution with respect to Herschel (more bright/"blue" material west of Herschel than north or south) may allude to a different origin. The color differences could be result of changes in composition (if ejecta, material from deeper within Mimas) or due to differences in grain size.

Mimas Rev12 Images

2005-08-04T11:45:00.000-07:00

Just a reminder for posts from the last few days, regarding images taken of Mimas:

Also check out the DEM of Morgan crater (below center in the above images), produced from photoclinometry, or shape-from-shading. These were done by malgar and Bjorn Jonsson over at the unmannedspaceflight.com forum. There is also an anaglyph available.

Present-day oceans on Titan put to rest?

2005-08-04T08:29:00.000-07:00

A paper in today's issue in the journal Nature, puts to rest the idea that large parts of Titan's surface are currently covered in methane/ethane oceans. Several years ago, a paper by Campbell et al. in Science, presented evidence for wide-spread liquids on the surface of Titan from specular reflections seen in radar pulses sent from Arecibo. The paper, West et al., in today's issue of Nature uses near-infrared observations near 2 microns. Like Campbell et al. they used ground-based observations to look for specular reflections along a wide-range of longitudes near 25 South Latitude. They found no evidence of specular reflections in their data. Specular reflections at near-infrared wavelengths would be much more conclusive for liquids on the surface than at RADAR wavelengths. For specular reflections to be seen, a surface must be smooth at the scale of the wavelength used to observe the surface. So for RADAR specular reflections, a surface only needs to be smooth on the order of 13 cm (or 3 cm for Cassini RADAR), which can be achieved by such terrain as a mud flat that contains only small, smooth rocks (think Huygens landing site). For a near-infrared wavelength specular reflection, terrain has to be smooth on the order of 2 microns, which is VERY difficult to achieve with anything but a liquid surface. So the absence of a specular reflection at near-infrared wavelengths would seem to rule out liquids at 25 South latitude. The presence of a RADAR specular reflection may indicate that some of these areas are covered in mud flats (or regions without large boulders or rough terrain), perhaps indicating that liquids were present in the past.

There are some pathological cases where you could have a liquid covered in floating crude, but very few materials can float on liquid methane, except perhaps acetylene, but it still has to overcome the low surface tension of methane. Additionally, this study only looked at liquids at 25 South. This leaves open the possibility that liquids may exist seasonally at the poles as they receive enhanced rainfall.

UPDATE: 08/04/2005 12:45pm: New Scientist has a more in-depth article online for those without subscriptions to Nature.

New Tethys Image: Texture of Tethys

2005-08-04T08:00:00.000-07:00

CICLOPS has released this processed view of Tethys taken on June 27. This view shows the impact basin, Odysseus, near the dawn terminator at the time this image was taken. Being right on the terminator allows for detailed analysis of the structure of the eastern portion of the basin. For example, one can see a number of massifs near the central peak region and look at the complex layered appearance of the eastern basin rim. This image was taken from a distance of 490,000 km and has a resolution of 3 km/pixel.

Next Set of Mimas and Dione images

2005-08-03T15:05:00.000-07:00

The next set of Mimas and Dione images will be linked to here as they come in..

Mimas Images on Ciclops website

2005-08-03T08:49:00.000-07:00

The Cassini Imaging website now has a page of preview images from the Mimas encounter. These are the same images on the JPL raw images page, but without the nasty JPEG artifacts. So be sure to check those out. There is also a map showing intended coverage for the images returned last night and those coming up this afternoon.

Again, the next set of images should start showing up around 1:30pm. Check this site for news and update as they occur throughout the day.

BTW, that's 1:30pm Pacific Daylight Time.

Dione, Rhea, and Mimas raw images

2005-08-02T19:58:00.000-07:00

Raw images from the non-targeted encounters of Dione, Rhea, and Mimas should start showing up this evening with a second batch tomorrow morning.

Watch this space for raw images as they show up on the JPL Raw images page.

That appears to be it for the night! Come back tomorrow afternoon, around 1:30 pm PDT for more Mimas images.

50,000th Hit and Anniversary

2005-08-02T09:09:00.000-07:00

Just noticed that the hit counter went over 50,000 over night, signalling a major milestone for this website. Titan Today has been on the web for only 6 months and has garned more interest than I could have ever expected. I did not design this website for everyone, it was designed for people interested in a little more of the "nitty-gritty" of outer solar system planetary science and the Cassini mission. The fact that so many people visit the site I feel is an indication of the interest in such unmanned missions, missions that continue the human desire to explore, reach out, and see what is beyond that next hill, not necessarily because the valley over might have microbes, but because it is THERE!

Anyways, I also wanted to say Happy Anniversary to my parents! They have been together for 30 years now, absolutely amazing. Congratulations to you both and I hope you have a great anniversary!

First set of images from Mimas Rev12 Encounter

2005-08-01T16:50:00.000-07:00

Raw Images from the Mimas Encounter are starting to come down. These early images are from 840,000 km out so these are pretty low resolution, but cover the terrain we will be seeing at much higher resolution one Mimas day later. The large crater at lower left is a 70-km wide crater named Arthur (named after the legendary King Arthur). The smaller crater at about 3 o'clock is named Morgan (~43 km wide).

More images should come down tomorrow and Wednesday.

Also, don't forget to check out this view of Tethys with Odysseus edge-on :=O In case you couldn't tell from this post, the JPL Raw images page has been updated!

UPDATE: 08/02/2005 09:10am: Just a note that images will not start showing up till later this evening PDT.

Rev12 Mimas Encounter

2005-08-01T11:32:00.000-07:00

This evening PDT, Cassini will make its closest approach to Mimas for the entire nominal mission. At 9:46pm PDT (ERT), or 04:22 UTC SCET, Cassini will fly within 62,074 km of Mimas' battered surface. This will provide Cassini's best look at Mimas for the entire tour and will provide some of our first decent views of this satellite's south polar region. The south pole of a number of satellites have been highlighted for the last few orbits due to Cassini's currently high inclination. Unfortunately, Mimas is the only major satellite that does not get a targeted flyby in the nominal tour, and unless something major is found during this pass, I doubt it would be a target for one in an extended mission. In addition to Mimas, Dione and Rhea non-targeted encounters are highlighted on this orbit.

Mimas is a relatively small satellite, only 400 km across. Its surface is heavily battered, with numerous impacts filling the surface to saturation. Its near twin in the Saturnian system, Enceladus, has some heavily cratered regions, but even those areas on its surface appear younger than Mimas. Some tectonic chasms can be seen criss-crossing its surface, including one east of Herschel, known as Camelot Chasma, and Ossa Chasma shown above. Unlike Enceladus, where tectonic fractures are likely related to internal heat, fractures on Mimas, given its heavily cratered surface, are likely related to stress caused by Herschel and other large impacts.

This encounter of Mimas will highlight the anti-Saturnian hemisphere of Mimas, particularly the southern regions. At the start of the encounter, Herschel will be near the evening terminator and will cross it and start to go beyond the limb as the encounter progresses. As Herschel pulls out of view, another large crater known as Arthur will pull into view. To the southwest of Arthur is another large central peak crater named Merlin. As we approach Mimas, more of the northern hemisphere comes into view, providing a good look at regions not seen by Voyager and toward a crater known as Morgan. As we pass closest approach we are left with a decent look at the northern reaches of the trailing hemisphere.

Mimas isn't the only world to be highlighted during this orbit. Today, Cassini flys within 206,000 km of Rhea and Dione. Rhea's south polar region, like during the last orbit, should be on full display, but this time the trailing hemisphere will be lit. Images of Dione's wispy terrain could be obtained during this encounter.

UPDATE: 12:35pm: some of the links farther down don't work because Blogger likes to reformat my links. I will try to find a correction... links fixed.

UPDATE: 1:05pm: Björn Jónsson has produced an animation showing the geometry of the Mimas encounter that is definitely worth checking out. The file size is 7MB but is worth the download.

New Rhea Image: Rhea's Bright Blemish

2005-08-01T08:50:00.000-07:00

CICLOPS has released this view of Rhea taken on June 25 and was discussed here after it showed up on the JPL Raw images page. This view shows Rhea at a phase angle near zero, meaning the Sun was almost directly behind Cassini's camera when this shot was taken of Rhea. At phase angles that low, little topographic relief can be seen, only albedo variations. This allows such features like the streaks radiating out from a relatively fresh crater seen here to appear so prominently. Craters can be seen despite topographic shading not being visible. Crater walls are often sites of rugged terrain, allowing for more shadowed regions compared to flat areas. So water is preferentially removed from flat, smooth areas, and deposited in areas that are more often than not, in shadow. This process is especially strong on Callisto and Ganymede, where frost from flat areas and slopes that face the equator is removed and is deposited in poleward-facing slopes.

Planetary Society: Enceladus: South Polar Stripes Spew "Warm" Water

2005-07-31T12:14:00.000-07:00

The Planetary Society website has an article by Emily Lakdawalla on the recent discoveries made at Enceladus by the various instruments on Cassini. The article includes information from the three press releases from this past week as well as an interview with deputy project scientist Linda Spilker. The article is a pretty good summary of the results obtained a couple of weeks ago and contains a nice overview of the CDA results that have been discussed here in the comments. Definitely worth reading.

Press Release: Cassini Finds an Active, Watery World at Saturn's Enceladus

2005-07-29T18:20:00.000-07:00

JPL has put out a press release describing the results from July 14 Enceladus flyby. In addition to the CIRS, MAG, and UVIS results mentioned here in other posts from today, INMS and CDA results are described. INMS, which normally looks at Titan in order to measure the composition and density of its upper atmosphere, found that Enceladus' atmosphere is composed of 65% Water vapor and 20% molecular hydrogen, with trace amounts of methane, carbon dioxide, and a combination of nitrogen and Carbon Monoxide (both molecules have the same mass so INMS can't distinguish between the two). The presence of Water vapor in its molecular form and the absense of atomic oxygen (also seen by UVIS), suggests that Enceladus' atmosphere is created from outgassing or evaporation at areas of elevated temperatures, and not from sputtering or impacts, like Europa's atmosphere. INMS also found spatial variations, both between regions near the south polar region and away from, and in layers, suggesting that there is a localized source of the atmosphere in the south pole, results that jive well with the MAG and UVIS data.

The CIRS data is the kicker. CIRS made temperature measurements both in dedicated scans and as ride-along observations with ISS. In both measurements, elevated temperatures were found in the south polar region near the tiger stripes and particularly within the tiger stripes. Color temperatures suggest that some areas in the tiger stripes could be as warm as 140K, indicating that the tiger stripes are regions of escaping internal heat. Such observations are indications that Enceladus is one of only three moons in the outer solar system with active volcanism (though the jury is still out with Titan, no elevated surface temperatures have been found there).

The CDA instrument found that dust kicked off by micrometeorite impacts are the source for the E-ring. Now, I should clear up some confusion brought up when comparing the atmospheric and dust results. Gas particles that make up the atmosphere appear to be generated by evaporation of warm ice or outgassing. The impact-generated cloud that forms the source of the E-ring consists of dust-sized particles, which are different from the atmosphere discussed earlier. The gases produced during a micrometorite must not be generated at a fast enough rate to be a significant contributor to Enceladus' atmosphere.

Off-topic: Tenth Planet Found

2005-07-29T18:00:00.000-07:00

Busy day today, news wise. First we have active venting found on Enceladus announced. And now, a new planet! News reports have been circulating today regarding a newly found Trans-Neptunian object called 2003 EL61. Early reports, from a team of astronomers led by Jose Ortiz, suggested that the object was perhaps as large as Mars. However, a team led by Mike Brown announced that results from Spitzer suggested that 2003 EL61 is much smaller, maybe 1500 km across, smaller than Pluto. In addition, a much smaller moon was found orbiting 2003 EL61. By measuring the orbital period (49 days) and the orbital distance, Brown's team found the mass of the system to be only 30% of Pluto.

But that's not what I am talking about. I am talking about another discovery made by Mike Brown's team, 2003 UB313. A lower limit of the size for this object is a little larger than Pluto, meaning this world is definitely larger than Pluto. Size estimates assuming an albedo of 0.25, or around the albedo of other large bodies in the Kuiper Belt suggest a size around that of Mars.

So definitely an exciting discovery. Again, because this is off-topic from the discussion of outer planet satellites, I will limit discussion of 2003 UB313 to this post, unless of course a moon is found...

UPDATE: 07/29/2005 6:25pm: JPL has a press release now on their site about 2003 UB313. The new planet appears to be 2600 km across with bounds of around 2300 km (assuming it reflects all the light it receives from the sun, an unlikely proposition) and 3000 km (because it failed to be detected by Spitzer). Spectroscopy of 2003 UB313 indicates the presence of methane ice on the surface. In addition, Mike Brown's group has a website about the new planet that might be worth monitoring for the next few days, as well as the Wikipedia page.
UPDATE: 07/29/2005 8:08 pm: Planet not named Lila nor is the proposed name Lila. Please disregard.

New Enceladus Image: Warm Fractures on Enceladus

2005-07-29T15:30:00.000-07:00

CICLOPS and the Composite InfraRed Spectrometer (CIRS) team have released this view of Enceladus in coordination with today's press release. During the flyby on July 14, CIRS took spectral measurements at wavelengths between 9 and 16.5 microns to measure the surface temperature of Enceladus, often coinciding with images taken by ISS. A string of ride-along measurements are shown here, superimposed on a ISS false color image taken at the same time as the measurements. The boxes represent the location of the measurements and the numbers above represent the temperature measured in Kelvin. Most of the surface was found to be in the expected range of 75K, however regions in the south polar ridged terrain showed higher temperatures. A couple of measurements, seen here, were a much higher temperatures, between 87 and 91 Kelvin, which is difficult (but not impossible) to explain by solar heating. When looking at the color temperatures measured, which looks at the shape of the spectrum seen by CIRS to determine the temperatures of several sub-pixel components. A two-temperature fit to the spectrum results in at least 1 percent of the 91 K pixel having a temperature of 140 K, further supporting the hypothesis that the increased temperatures seen over this area of the tiger stripes is caused by heat escaping from Enceladus' interior.

The ISS view is a false color version of the clear filter image released earlier this week and has a resolution of 122 m/pixel. This image uses an ultraviolet filter for blue, the clear filter for green (the normal green filter image was summed), and a near-infrared filter for red. The area surrounding the tiger stripe fracture is thought to be bluer because of coarse-grained water ice that has not been covered by the fine-grained ice that has painted the rest of Enceladus' surface.

UVIS Directly Measures Enceladus' atmosphere

2005-07-29T11:40:00.000-07:00

After not sensing the atmosphere during an occultation in February, UVIS finally observed the atmosphere first observed by the magnetometer instrument. The UVIS detection came during another stellar occultation, this time of gamma Orionis, or Bellatrix. This star turned out to be a much better one to use than the star used in February, Lambda Sco. During the occultation, UVIS measured the intensity of the star as it passed behind Enceladus and its atmosphere, then reappeared following the occultation. Measurements during ingress (or approaching occultation) indicated a UV absorber between Bellatrix and Cassini over Enceladus south polar region, indicating an atmosphere composed of water vapor. Measurements during egress (or following the occultation) over nightside equatorial regions of Enceladus did not show nearly as strong of a UV absorber. This measurements fits well with the MAG models indicating that the atmosphere is not uniform over the surface of Enceladus and is likely concentrated over the south pole. The lack of a detection during egress could also result from the atmosphere "freezing out" at night.

The presence of water vapor in Enceladus' atmosphere and the lack of atomic oxygen indicates that the atmosphere is produced from the venting or evaporation of water ice from the surface rather than from magnetospheric sputtering, as is the case for the rarefied atmospheres of Europa and Ganymede. Instead the atmosphere has more in common with Io.

Hot Spot found on Enceladus

2005-07-29T11:19:00.000-07:00

The CIRS instrument released this view of Enceladus. The image on the left is based on a model assuming a sub-solar temperature of 80 Kelvin, then cooling as you approach the terminator. The view on the left is the brightness temperatures actually measured by CIRS at wavelengths between 9 and 16.5 microns. The equatorial temperatures were as expected, again with temperatures around 75 Kelvin. Surface temperatures then cool to around 65 Kelvin as you approach the south polar region. However, in the south polar region, the temperature dramatically increases, to brightness temperatures of around 85 Kelvin, 15 degrees warmer than expected. The detector footprint at this distance was 25 km. Color temperatures from this data reveal small regions on the surface at well over 110 Kelvin.

The temperatures found in the south polar terrain are too warm to be caused by heating from sunlight alone, though exotic sunlight-trapping processes have not been ruled out. This means that heat from Enceladus' interior is escaping in the south polar region. The temperature would also be warm enough to produce evaporation of water ice at the surface, consistent with UVIS and MAG measurements of a concentration of Enceladus' atmosphere in the region.

This data makes Enceladus only the third body in the solar system (including the Earth and Io) where heat escaping from the body's interior has been found.

Press Release: Magnetometer instrument confirms Enceladus' atmosphere

2005-07-29T11:00:00.000-07:00

The Cassini Magnetometer team, using data from the very close flyby on July 15, have confirmed the atmosphere first seen during the two earlier flybys in February and March. Based largely on the MAG data obtained during those flybys, the altitude of the July flyby was lowered from 1000 km to a scant 175 km. With this new data in hand, and with improved modeling of the earlier data, the MAG team was also better able to constrain the nature of the atmosphere. Rather than a uniform atmosphere across the surface of Enceladus, the Magnetometer results are most consistent with a neutral cloud of gas concentrated over the south polar region of Enceladus. ISS images of the region showed a very young surface with numerous tectonic fractures and strange "chunky peanut butter-like" terrain. Away from the south polar region, the atmosphere is much thinner. These results indicate that Enceladus' atmosphere is similar to that of Io's, where point sources, in Io's case volcanoes, pump gases into space which then spreads out across the surface or escapes the satellite's gravitational pull entirely. This leads to significant differences in atmospheric density across the surface. The press release compared the concentration to that of a cometary jet, though there is no evidence that it needs to be THAT concentrated of a source. Perhaps there are several sources spread out over a similar area (20 degree half-width).

The press release also mentions that other Cassini instruments found an atmosphere at Enceladus, though it didn't go into specifics. UVIS had a stellar occultation at closest approach designed to look for the atmosphere and other fields-and-particles instruments, like INMS, were on during the encounter.

DPS 2005 Abstracts online

2005-07-29T10:14:00.000-07:00

Abstracts for the Division of Planetary Sciences (DPS) meeting in Cambridge, England in early September are now online. DPS abstracts are much shorter than LPSC abstracts (which are practically mini-papers) and are notorious for saying everything and nothing. However, there are some interesting talks and posters described here, that I would view, if I were going... For vanity purposes, the abstracts I am a co-author, and thus will be very disappointed if you don't go to if you are attending the conference (I'm not going, but I'll know, trust me, I'll know).

INMS Titan Observations by Waite et al.
* Geological Features and Terrains on Enceladus as seen by Cassini ISS by Helfenstein et al.
* Mapping and Monitoring the Surface of Titan by McEwen et al.
* The Brightest Spot on Titan by Barnes et al.
Correlating hotspots on Io with surface features using Galileo eclipse images by Radebaugh et al.
Gravity Science In The Saturnian System: The Masses of Phoebe, Iapetus, Dione, and Enceladus by Rappaport et al.
Cassini VIMS compositional mapping of Surfaces in the Saturn System and the role of water, cyanide compounds and carbon dioxide by Clark et al.
Aromatic Hydrocarbons on Iapetus and Phoebe: Cassini-VIMS Detections by Cruikshank et al.
Unusual Spectral Behavior of the Saturnian Satellites at Long Thermal Wavelengths by Pearl et al.
A Geophysical Study Of Iapetus: The Need For And Consequences Of Al26 by Castillo et al.
The geology of Saturn's satellite Dione observed by Cassini's ISS camera by Wagner et al.
Full-disk observations of the Saturn's icy moons by Cassini/VIMS by Filacchione et al.

New Enceladus Image: Zooming in on Enceladus

2005-07-26T06:56:00.000-07:00

CICLOPS has released this huge mosaic of the surface of Saturn's moon Enceladus. This mosaic was produced using 21 "footprints" of images taken during last week's encounter. Each footprint consists of images taken in a filter sensitive to ultraviolet light at 338 nanometers, a filter sensitive to infrared light at 930 nanometers, and either a filter sensitive to green light at 568 nanometers or a clear filter. This image contains much of the higher resolution images taken by Cassini during this encounter. The mosaic resolution is 134 meters/pixel, but it contains images that have original resolutions of up to 67 m/pixel.

In addition to the large mosaic, produced over the weekend by yours truly, is a fantastic movie zooming in on the mosaic, onto the highest resolution images taken during the UVIS occultation. The highest resolution images were taken below (in the large mosaic) the left most tiger stripe in a belt of tectonic grooves. You can see the location in the movie.

Press Release: Close Cassini Flyby Hints at Unusual Tectonic Activity on Enceladus

2005-07-26T06:55:00.000-07:00

CICLOPS has now posted some initial results from images taken during last week's flyby of Saturn's strange icy moon Enceladus. Whereas the previous two encounters highlighted features seen in the equatorial regions of Enceladus, this encounter focused on terrain near the south pole of Enceladus. Previous images of the region taken by Cassini showed some interesting features, but it wasn't until now that these features were seen at geologically useful resolutions.

From the press release:

New detailed images taken by NASA's Cassini spacecraft of the south polar region of Saturn's moon Enceladus reveal distinctive geological features, and the most youthful terrains of any seen on Enceladus. These findings point to a very complex evolutionary history for Saturn's brightest, whitest world.

Cassini's flyby on July 14 brought it within 175 kilometers (109 miles) of the surface of the icy moon. The close encounter revealed a landscape near the south pole littered with house-sized ice boulders, carved by tectonic patterns unique to Enceladus, and almost entirely free of impact craters. These features set the southerly region apart from the rest of the moon.

Several lines of evidence are discussed that point toward a youthful age for Enceladus. While absolute ages have yet to be determined due to a lack of understanding of the cratering function for the Saturnian system, circumstantial evidence such as the lack of craters larger than 1 km and the paucity of craters smaller than that and the rough appearance at very high resolution, including building-sized boulders, the lack of fine grained material. Enceladus should be an interesting but challenging world to geologically map, but Enceladus has thrown us a bone. Many of the geologic regions are topographically and morphologically distinct, such as the south polar region with its wavy boundary with several y-shaped features filled with folded terrain. Dr. Paul Helfenstein suggests that suggest that such a boundary, located at around 60 degrees South latitude, could be the result of changes in the global stress pattern due to despinning. Such geologic features he contends "may tell us a very interesting story about the way Enceladus has evolved over time and what might have provided the energy to power the geologic activity that has wracked this moon".

UPDATE 12:30 pm: Usually I post links to news articles of news organizations covering releases like this. Unfortunately, I have found that only spaceref.com even has a copy of the press release, let alone did a story of their own. Everything today is about the Shuttle launch.

New Enceladus Image: Boulder Strewn Surface

2005-07-26T06:53:00.000-07:00

CICLOPS has released several processed views using the highest resolution images taken thus far of Saturn's moon Enceladus. In the combined view above, the image at lower left is an expanded view of the wide-angle image and the inset image is the narrow angle view taken at the same time. Both images were taken when Cassini was at an altitude of 208 km above Enceladus' icy surface, but because Cassini was looking at the limb at the time, the actual distance to this area on the surface was 319 km. Thus the resolution of the narrow angle view was 3.7 m/pixel while the wide angle view has a resolution of 37 m/pixel.

The images themselves show a tectonically tortured region near the south pole of Enceladus. The lack of craters here, and the paucity of craters elsewhere in the region suggests that this area is geolgically young. In the narrow angle view, numerous boulders, 10-100 meters across, can be seen. How such boulders were produced in a relatively crater-free region will be a focus for study. The fact they have not been eroded by space weathering is another indication that this region is very young.

New Enceladus Image: Tiger Stripes Up Close

2005-07-26T06:52:00.000-07:00

CICLOPS has released this high resolution frame showing the "tiger stripes" near Enceladus' south pole. These stripes were first seen as albedo features in images taken in May (though their northern ends could be seen in images taken in March). This image has a resolution of 122 meters/pixel and was taken from a distance of 20,720 km from Enceladus. It shows the tiger stripes to be fractures cutting across the Enceladean south polar region with ridges on each side of the fractures in many cases. The tiger stripes are distinctive in color observations as blue-green stripes. Blue-green terrain, thought to be coarse-grained water ice, has been observed in other region within bed-ice outcrops and canyon walls. Here, the blue ice appears to be a mattling, not just in fractures, but in relatively flat terrain as well. The cause for the difference in distribution is still under investigation.

New Enceladus Image: Enceladus In False Color

2005-07-26T06:50:00.000-07:00

CICLOPS has released this processed, lower resolution color image of the full disk of Enceladus, as seen during last Thursday's flyby. This image was taken from a distance of 112,100 km and has a resolution of 670 m/pixel. It is centered at 42 degrees South, 167 degrees West, showing mostly the southern anti-Saturnian hemisphere of Enceladus. This image shows the south polar region in all its glory. Unlike the cratered region in the northern part of the disk, the south polar region has very few craters that can be resolved at this resolution. Instead the area is covered in fractures of all sizes. The south polar region is even seperated from the surrounding terrain by a wavy boundary characterized by tectonic gashes and by "'Y-shaped' tectonic patterns that appear to engulf folded regions of ridges and troughs.

This is a false color view created using image taken in an ultraviolet filter centered at 338 nm, a green filter at 568 nm, and an infrared filter centered at 752 nm (most other false color views use one centered at 930 nm).

New Enceladus Image: Craters and Cracks

2005-07-26T06:49:00.000-07:00

CICLOPS has released this view of Enceladus show heavily modified craters and fractures along the northern edge of the South Polar tectonic region. This is the highest resolution image taken before the UVIS occultation ride-along image. Near the top of the image, numerous craters can be observed, most covered in tectonic fractures and cracks. Such morphology has been observed throughout this region of Enceladus, suggesting intense stresses following the initial formation of the south polar terrain. Also note the relative lack of rough terrain in the cratered region (outside of the thin fractures), quite different from the region of large boulders seen in the highest resolution images, also released today. In the lower part of the image, relatively few craters are seen and all are much less than a kilometer across.

This image has a resolution of 67 meters per pixel and was taken from a distance of 11,500 km.

New Scientist: Has Huygens found life on Titan?

2005-07-25T09:09:00.000-07:00

Now, for the crank story of the day. New Scientist has a story online regarding the possible existence of hydrogen-breathing microbes on the surface of Titan. The story is based on a preprint of an article to be published in Icarus by Chris McKay and Heather Smith. They discuss the possibility that microbes on the surface of Titan could derive their energy from breathing hydrogen and "eating" acetylene that falls from the upper atmosphere on to the surface. They further suggest that depletions in both hydrogen and acetylene near the surface may betray the presence of such organisms. These types of measurements were made by the GCMS instrument on Huygens in January. Hasso Niemann, the PI for the GCMS instrument, stated that the hydrogen abundance is still being worked out and that an upper limit should be arrived at soon.

Of course this article fails to explain how you get around a 94 K surface temperature at the landing site....

New Prometheus Image: Lumpy Prometheus

2005-07-25T08:47:00.000-07:00

CICLOPS has released this view of Saturn's small inner moon Prometheus. Prometheus orbits on the inner edge of the F ring. In this view, you can clearly see Prometheus' irregular and oblong shape. Prometheus is only 102 km across and is too small for its gravity to pull itself into a spherical shape. Several craters are visible in this view of Prometheus' southern anti-Saturnian hemisphere. This image has a resolution of 3 km/pixel (though it has been magnified 2x to aid visibility) and was taken from a distance of 438,000 km on June 7, 2005.

Raw Images of the Day

2005-07-21T11:26:00.000-07:00

Like the turning of the hourglass.. here are the raw images of the day:

New Helene Image: Helene from Afar

2005-07-21T08:30:00.000-07:00

CICLOPS' daily release today is this processed view of Saturn's moon Helene. Helene is another small trojan moon, like yesterday's daily release Telesto, but instead of being a trojan of Tethys, Helene is a trojan moon of Dione. Helene orbits at the same distance from Saturn as Dione, but 60 degrees ahead in the orbit, at the L4 Lagrange Point. This image has still too low of resolution to show surface features, but the overall shape of the moon can be seen. This image has a resolution of 5 km/pixel but has been magnified by three times to aid visibility.

Press Release: MIT-Williams team catches rare light show with Charon

2005-07-20T16:27:00.000-07:00

A group of astronomers from MIT are reporting the successful acquition of data during a stellar occulatation by Pluto's moon Charon on the night of July 10-11. The data was taken using four different telescopes in Chile, as well as one in Brazil. The data from occultation should help to constrain the size of Charon, as well determine if the satellite has an atmosphere.

More information can be found on the MIT website.

T7 flyby altitude raised

2005-07-20T15:28:00.000-07:00

I haven't mentioned this before on this page, but last week's Cassini Significant events update reported that the altitude of the T7 flyby, set to take place on September 7, has been raised from 1025 km to 1075 km, based on the recommendation of the Titan Atmospheric Modeling Working Group. There is concern that the haze layer over the summer hemisphere may be inflated compared to the winter hemisphere. All close approaches of Titan thus far have been over the northern hemisphere, the current winter hemisphere. The Cassini data that has gone into the atmospheric model has thus been mostly from the northern hemisphere. So to prevent a safing event caused by a loss in attitude control, the flyby altitude has been raised. Such an increase could lead to issues with mosaic and swath designs for ISS, VIMS, and RADAR as they make observations during the flyby.

New Scientist: Bizarre boulders litter Saturn moon's icy surface

2005-07-20T10:12:00.000-07:00

New Scientist has an article now posted regarding the highest resolution ISS image of Enceladus. Some interesting comments, though one needs to very careful about making assumptions that this kind of surface is common on Enceladus until you see where the frame is on the surface, for context. And in terms of making interpretations this early, I think Zibi Turtle said it best:

But Elizabeth Turtle, a Cassini imaging team member at the University of Arizona in Tucson, US, warns there will be no quick answers. “Trying to figure out what is going on is going to take a lot longer than a weekend of swapped emails,” she says.

My bloated inbox certainly understands...not that I am complaining :D

New Telesto Image: Trojan Telesto

2005-07-20T09:43:00.000-07:00

CICLOPS has released this highest resolution view of the Tethys trojan Telesto. This moon, only 24 kilometers across, has not yet been seen at high enough resolution to resolve surface features, but images such as this one do allow for the beginning of shape modeling. Higher resolution images should come later this year during encounters that bring Cassini within 20,000 km of this moon.

New Cassini Image: F Ring Shepherds

2005-07-20T08:56:00.000-07:00

This view of the F-ring was released by CICLOPS on Monday. This image shows both F-ring shepherds, Pandora on the left and Prometheus on the right, in the same view. While this view has too low of resolution, the serealistic view highlights their relationship to the F-ring.

Enceladus thoughts and more

2005-07-17T15:18:00.000-07:00

Just giving everyone a heads up: I will be out of town starting tonight and will be in Flagstaff for a Titan Surfaces Meeting until Tuesday evening. While I am at it, yes Dad, I got the package. Thanks for the cookies! Anyways, my connection to the internet maybe spotty so don't expect too many updates here over the next couple of days.

On to Enceladus. This little moon continues to amaze. The views of this moon's south polar region were spectacular, including one very high resolution shot taken from a distance of only a few hundred km. Immediately one thinks of Europa, but one has to be careful comparing two very differently sized worlds. I can't count out the possibility of a liquid ocean, but the small size of Enceladus and the prevalence of cratered terrain makes me think that is not what we are see here. I think a more apt analogy is Miranda, with its own dichonomy between concentric ridged corona and heavily cratered terrain. In the case of Miranda, it is thought that upwellings of warm ice produced the coronae. A similar formation mechanism could be invisioned for Enceladus.

Highest Resolution images of Enceladus

2005-07-15T21:30:00.000-07:00

The JPL Cassini site has this image on their front page. This is a wide-angle image from the UVIS occultation ride-along. I felt this deserves its own topic if only because this is the wide-angle image, imagine what the narrow angle image will look like.

This wide-angle image has a resolution of approximately 20 meters/pixel.

Update: the NAC view is now available. this image has a resolution of 2 m/pixel. You can clearly see several large boulders in a region of high tectonic deformation. The WAC image that was above can still be seen on the JPL Cassini Front Page.

Enceladus-2 Raw Images

2005-07-15T21:25:00.000-07:00

I'll post the best raw Enceladus images when they become available.

The Cassini website has the following posted as of 2:12pm PDT:

The Cassini spacecraft conducted its closest flyby yet, coming within 175 kilometers (109 miles) from the surface of Enceladus. Data collected is currently being downloaded. Raw images are expected to appear on this web site at around 10 p.m. PDT.

UPDATE: 4:30 pm: The last of the Rhea images are showing up on the JPL raw images page now. Next up, Enceladus...
UPDATE: 4:50 pm: It has begun...
UPDATE: 5:00 pm: CICLOPS has begun post some select raw images from yesterday's flyby. So check out 10 of these at the CICLOPS website. I have put my favorite above. Trust me, it gets better....
UPDATE: 8:40 pm: Most of the NACs should be up soon. here is a list of interesting images thus far:

Obviously, feel free to post your favorites in the comments for this post!
UPDATE: 09:30 pm: Here are a few more (and Epimetheus):

Enceladus-2 Coverage Map

2005-07-15T11:40:00.000-07:00

CICLOPS has released a coverage map for yesterday's encounter with Enceladus. The colored outlines represent regions on the surface of Enceladus that will be imaged by Cassini's narrow angle camera. This map does not include images taken during a "ride-along" sequence with UVIS' Gamma Orionis occultation at close approach. As you can see from this map, most of the images planned are of the southern trailing hemisphere of Enceladus, with some distant imaging of the leading hemisphere ridged plains. The highest resolution prime observations (prime observations mean that the imaging team will be controlling the orientation of the spacecraft during a block of time) will be of a region of heavily tectonically deformed terrain near 60 South, 190 West.

Note, due to unplanned changes in the orientations of the camera, the region that will be imaged could shift slightly from the outlines shown above. This mainly effects regions where the frames are much smaller than the disk, not so much the region outlined in red.

On a related subject, the JPL Cassini Website has a flyby page for this encounter. Check back here or on that page for the latest from other Cassini instruments, if and when they release products.

Rhea images starting to show up

2005-07-15T08:49:00.000-07:00

The first of the Rhea images taken before yesterday's Enceladus flyby are starting to show up. Above is an example of one of the early images showing the full disk of Rhea. At its peak, images with resolutions up to 1 km/pixel should show up. The region seen here is the southern leading and anti-Saturnian hemisphere. South is to the right. More images to come.

UPDATE: most of the Rhea images downlinked this morning are now down, suggesting a 8 hour lag between when the images are downlinked and when they are posted on the JPL raw images page. The available images show a largely cratered landscape with several large impacts, one with a nice central peak.

Enceladus Flyby Today

2005-07-14T15:03:00.000-07:00

The Enceladus flyby took place 3 hours ago so most of the data from the flyby should now be onboard the spacecraft :D We will have to wait till tomorrow for the data so make sure to come back here tomorrow afternoon and Saturday for the latest on the Enceladus-2 flyby.

New Titan Image: Clues in the Bright and Dark

2005-07-14T08:58:00.000-07:00

CICLOPS has released this view of Titan taken by Cassini on June 4, 2005 from a distance of 1.2 million km (for a resolution of 7 km/pixel). This view was taken shortly before the "lake" image, and was discussed here last month. This image shows surface features in and around the large bright region known as Xanadu. Xanadu here is fairly mottled with small dark spots along with regions of brighter terrain, like the "smile"-shaped surface feature. The "Smile" was also seen by VIMS during T4 and T5 and was found to be the bright feature on the surface of Titan at 5 microns. The bright area at 4 o'clock is actually a patch of clouds, perhaps the same area of clouds seen a day later in the lake image released earlier.

Raw Images of the Day

2005-07-13T10:42:00.004-07:00

Only a few more days till the Enceladus encounter and orbit 11 periapsis so the moons are starting to get larger in the window...

Leading hemisphere of Rhea (north is to the upper right)
Leading hemisphere of Tethys (between Odysseus and Ithaca Chasma, you can just see the eastern rim of Odysseus near the terminator, north is to the upper right)
Leading hemisphere of Enceladus (terra incognita, north is to the upper right)
Leading hemisphere of Dione (south polar impact basin at 9 o'clock, north is to the right)
Tethys' Odysseus impact basin near terminator (excellent topography seen)
Sub-Saturnian hemisphere of Enceladus
East of Ithaca Chasma on Tethys
Leading hemisphere of Mimas (Herschel near terminator, north to right)
Sub-Saturnian hemisphere of Mimas (Herschel just beyond the terminator)
Wispy terrain on Dione
Trailing hemisphere of Enceladus (bright region is the leading hemisphere ridged plains)

Concession Speech

2005-07-13T10:36:00.000-07:00

The votes have been tallied and the results are in: the colorized surface photo of Titan taken by Huygens is the winner of the Photo Contest held on the Cassini-Huygens website. While I never expected my two enterants, Encountering Iapetus and Titan Mosaic to win, I was shocked at the low poll results, I mean, I lost to a moon smaller than the city I live in :o No worries, I will be working on an image product over the weekend, that, if successful, will surely win a year 2 contest...