Friday, January 28, 2005

How Europe's Media Landed On Titan - Another Observation has another article on the media coverage of the Huygens landing by Daniel Fischer. While the TV coverage on ESA TV (simulcast on NASA TV) left much to be desired (this post by the way is brought to you by Alcatel), the up-close and personal coverage at ESOC during the landing was apparently much better according to this op-ed piece.

Thursday, January 27, 2005

Discussion on the Dark Terrain: Part II

Here is the second part on my discussion on Titan's dark terrain. This part will cover the Huygens insitu observation of this terrain.

With ISS and Keck having already shown that widespread liquids in the dark terrain was unlikely and Arecibo and Cassini RADAR perhaps finding a few isolated areas of surface liquid, it was up to Huygens to perhaps resolve the mystery of the dark material. Luckily, Huygens landed near a boundary between dark and bright material so that both types of terrain can be seen up close for easy and unambiguous comparison. Even better, Huygens landed in a dry patch of dark terrain. Features seen in the dark material from altitude such as dark streams between small patches of bright terrain and streamlined shapes to the larger bright patches within the dark terrain suggest that although the dark material at the landing site was dry, fluid had at one time flowed in the area. This is supported by the observation of channels in the bright terrain terminating at the boundary between dark and bright regions and by the eroded shapes of ice rocks in the vicinity of the Huygens. Images from the surface using the medium-resolution imager were affected by the lamp but suggest that the close up texture of the surface is akin to gravel or sand.

In addition to imaging, the GCMS instrument, the penetrometer on the SSP instrument, and the spectrometer on the DISR instrument examined the composition and texture of the dark material. Spectra from altitude by DISR shows that the terrain is mostly made of water ice with some kind of darkening agent. The data from the penetrometer on the Surface Science Package has been interpreted as showing that that dark material at the landing site was covered in a thin crust of material with icy sand below. This is consistent with the DISR-MRI view of the surface. Finally, the GCMS instrument, with its heated inlet, found methane percolated into the instrument after being heated up to boiling.

Putting together these data, it appears that the area where Hugyens landed as modified by fluids, possibly from rainfall during a rainy season but that's still an early hypothesis, especially since we have yet to see clouds at that latitude, perhaps since clouds have only been observed for a few years (though a large cloud may have been see at northern mid-latitudes by HST in 1995). However, the views from above and from the surface both suggest that the terrain has been modified by fluid flow and erosion. The GCMS, SSP penetrometer, and MRI images seem to indicate a dry initial surface layer of ice sand with liquid methane 15-30 cm below the surface mixed in with the ice sand in a kind of methane slushee.

Followup: Outer Planet Data Analysis Funding

I've just been told by a colleague and now see it confirmed on (link in title) that the Outer Planet Data Analysis funding was not cut to make room for other priorities in the budget, but instead those funds have been moved to another line in the budget for "administrative reasons." Whatever the cause, either bureaucratic or community uproar, those who already have grants in place from this program will still recieve them this fiscal year.

Mimas, Enceladus, and Rhea images

On the Gregg Williams' link I gave below, not only does he have a color version of today's press released image, but he also has false color images of Mimas and Enceladus, as well as a clear filter mosaic of Rhea, all taken the weekend after the Huygens landing. Not to put down Rhea, but the Mimas and Enceladus images really steal the show here. The Mimas image shows the comparatively large crater Herschel near the terminator, allowing just the rim and the central peak to catch sunlight. A great image of this "Death Star" moon. The Enceladus image are also great, revealing a grooved landscape almost completely devoid of craters (though there are some craters elsewhere on the satellite). Certainly a key question for the two Enceladus flybys over the next two months is why Enceladus can have such geologically modified areas as we see here and in images taken by Voyager 2, yet have relatively ancient terrain elsewhere on the satellite. I suspect the answer will be a bit more complicated than Ganymede, Mars, and the Moon, three other places with relatively ancient and relatively young regions on the same world. The Rhea mosaic is nice but unfortunately Rhea suffers from "Boring Sibling Syndrome". Rhea has a similar size and mass to Iapetus, yet the former lacks the giant equatorial ridge, the multiple impact basins, and most importantly, the prominent hemispheric albedo asymmetry the latter possesses.

DISR Ask an Expert with Mike Bushroe

There is a new page with answers to questions posed to DISR team members on the DISR website. These questions are answered by Mike Bushroe, a Senior Staff Engineer on the DISR team. While many of the questions and answers were related to the remote possibility of life on Titan, some of the Q and A's were actually useful ;) One question in particular was pretty important to myself and to those enthusiasts working on Huygens images in their spare time. The question related to whether the DISR team would be able to subtract out the haze in their images to produce a clear view of the surface. In Mike's response, he mentioned that DISR images are 12-bit lossy compressed images, as opposed to the 8-bit jpegs "raw" images posted on the net thus far. This is similar to the ISS raw images situation. The actual raw data is 12-bit but the images posted on the JPL raw images page is 8-bit (and a jpeg). Another response by Bushroe showed that Huygens did not seem to detect seismic activity (using the accelerometers in the SSP) on the surface of Titan. Anyways, despite all the questions about life, this turned out to be a good Q and A.

Followup: Spotlight on Mimas

Gregg Williams has a color version of the image post earlier today showing Mimas and Saturn's rings at the link posted above at the bottom of that page. These are very nice compositions, one taken at the same time as the image below and another one Mimas orbit later with the small satellite Pandora in the field of view. The captions for these images on the page also show that these images were taken this month, not last month.


I've realized in the last few posts that I tend to use a lot of acronyms that maybe not everyone is aware of. So here is a brief glossary of acronyms that have or may show up on this page:

ISS - Imaging Sub-System (Cassini's camera)
VIMS - Visual and Infrared Mapping Spectrometer (Cassini's remote spectrometer)
INMS - Ion and Neutral Mass Spectrometer (Cassini's insitu spectrometer)
DISR - Descent Imager and Spectral Radiometer (the camera on Huygens)
GCMS - Gas Chromatograph and Mass Spectrometer (the insitu spectrometer on Huygens)
ACP - Aerosol Collector and Pyrolyzer (instrument on Huygens)
SSP - Surface Science Package (on Huygens)
DWE - Doppler Wind Experiment
OPNAV - OPtical NAVigation images used by Cassini to determine position by looking at known targets

And this is why we use special filters....

There is a new opnav image of Titan taken yesterday up on the JPL Raw images page. The image was taken in the two clear filters on the Cassini Narrow Angle Camera and really doesn't show much thanks to the ubiquitous haze in the shorter wavelength filters. Occassionally these images can be stretched to tease out some bright/dark boundaries, but it is still pretty useless. Still, it's nice to know it's still there.

New Cassini Image: Spotlight on Mimas

This image is a great new view of Mimas with the rings in the same field of view has just be published in the Ciclops website and on the Cassini JPL website. The caption says that this image was taken on December 18, but I think it is much closer to January 18 since I remember seeing this image come down just after the Huygens landing. I will check and make sure.

Wednesday, January 26, 2005

Discussion on the dark terrain: Part I

Over the next three days, I'd like to present my thoughts on Titan's dark terrain, both in the views prior to Huygens and with Huygens data now in hand. In Part I, this post, I will present the pre-Huygens view and what data was used to form those hypotheses. In Part II, I will present the new Huygens data in context with what we knew before. In Part III, I will present a few models to explain the dark terrain as seen by Huygens (think post-Voyager Io with methane instead of sulfur, ammonia-water cryovolcanism instead of basaltic volcanism, and water volcanism instead of komatite volcanism (okay that may be going too far...)

On January 14, the Huygens probe landed on the surface of Titan within the large equatorial belt of dark material in anti-Saturnian hemisphere. The nature of the dark material on Titan has been important question for geologists ever since the first disk-resolved images of surface taken by HST were released in the mid-1990s. One of the more popular explainations prior to the Cassini mission was that the dark material consisted of seas of liquid methane and ethane. This hypothesis was supported by speckle imaging in the late 1990s by a group out of the Lawrence Livermore Lab using the Keck I telescope showing that the dark material had an albedo at 2 microns of around 2%.

A more conclusive remote test for liquids is to search for specular
reflections. A specular reflection can be seen when looking at the sun's reflection on a body of water while on a day at the beach. All that is required is that the surface be smooth at the wavelength of the light source. In this case, five seperate data sets can be brought to bear on this problem, four of which are known to this blogger. First, Campbell et al. used the Arecibo Radio Telecope in Puerto Rico to look for a specular reflection at a wavelength of 13 cm. They found specular reflections in some places, but not everywhere. Finding a specular reflection at 13 cm is not necessarily diagnostic of liquids, but it does mean that the surface in the areas where a specular reflection was seen had to be smooth at the scales of 13 cm. The RADAR experiment on Cassini also observed Titan at a different wavelength in late October. While this is not aware of any specular reflection seen by that experiment, it did see a region of very low radar reflectivity (nicknamed Cici's Halloween Cat) that might be a lake of liquid methane but the jury is still out on that. More diagnostic is the Keck and Cassini ISS data sets. ISS does have higher resolution, but Keck has better longitudinal coverage at the present time. In neither data set has a specular reflection been found, including in the dark terrain.

Does Titan Rain Methane?

Rainfall on Titan seems to be a popular topic for interviews these days and Astrobiology Magazine has yet another one, this time with Sushil Atreya, a member of the GCMS and ACP instrument teams from the University of Michigan. This one is actually more on why there is methane, where it came from, and how is it destroyed. An interesting read nevertheless.

Search for life signal on Titan

The BBC News Website published an article yesterday on the possibility that the methane on Titan has a biological origin, as has been offered as a possibility for Mars' atmospheric methane. Of course, Titan's surface is too cold for life as we know it since water would be as hard as rock at 94 K, but the sub-surface ocean mentioned in the post below (between 300 and 400 kilometers below Titan's surface) might be a possible abode for life that manufactures Titan's methane. While I don't think there is life there, the article does put forth a test by the GCMS experiment on Huygens that can resolve this: the ratio between Carbon-12 and Carbon-13.

Jonathan Lunine talks Titan, Huygens

Jonathan Lunine, a Cassini Interdisciplinary scientist from the University of Arizona, recently gave a webcast lecture, giving an overview of Titan and putting the early Huygens results into context. Many of the comments he gave were his personal views of the data returned so far. I took some notes during the webcast so here are some of the comments I thought were significant.
  • DISR images showed that the haze layer extended down to at least 20 kilometers, well within the troposphere. Before Huygens, the haze was expected to extend down to around 50-60 kilometers and that the atmosphere should be clear below the tropopause at an altitude of 40 kilometers, assuming a well-mixed troposphere.
  • The Gas Chromatograph and Mass Spectrometer (GCMS) instrument on Huygens failed to find ethane in the atmosphere or on the surface to within the sensitivity of the instruments. For the surface, this can be explained two ways. First, the ethane could simply not be there, either by draining away from the area where Huygens landed or the photochemical models for Titan's atmosphere overestimated the amount of ethane that would be produced in Titan's lower haze layers, and instead other simple products like acetylene were produced. The other possibility is that liquid ethane was there along with the liquid methane. Ethane's vapor pressure was 3 orders of magnitude less than methane given the instrument setup (GCMS had a inlet heated to 90 degrees Celsius while on the surface). So the inlet may not have been hot enough to vaporize enough ethane for GCMS to sense it. In the atmosphere, the thicker haze layer may mean that ethane is locked up in the lower haze layers rather than precipitating out of the haze.
  • Given the the thicker haze, the optical depth of the haze layer may be more than previously thought. The DISR team estimates that the haze may have an optical depth of 3-4 at 1 micron, compared to a value of 1 predicted before the mission. However, with such an optically thick haze, how can we see the surface in ISS images? I would certainly like to see how they arrived at that number. My first guess would be using the solar aureole imager.
  • Lunine offered an alternative hypothesis to explain the sharp spike in the SSP penetrometer data. Instead of a thin crust, as posited by the SSP team, Lunine thinks Huygens first came down on a grouping of ice pebbles seen in the surface images, then slid down and settled on the surface. However, the question I have is whether the accelerometer data, which shows a 15 G deceleration in 40 ms, supports that hypothesis.
  • In the last post, I mentioned that doppler data recieved on Earth directly from Huygens indicated that Huygens had a fairly rough ride above the tropopause. Lunine mentioned in his talk that DISR saw the solar aureole with the side looking imager, which in a normal orientation looks about 10 degrees above the horizon. This means that at higher altitudes, Huygens was swinging by as much as 60 degrees from normal, nearly at the collapse point for the parachute.
  • Finally, Jonathan Lunine discussed the developing ammonia story on Titan. A water-ammonia mixture has a lower melting point than pure water, so it takes less energy to maintain a interior liquid layer than if the layer was composed of pure H2O. This may help explain the non-zero orbital eccentricity of Titan, which would dissipate if the liquid layer, between the Ice-I surface layer and the higher pressure ice below, froze. A conformation of an interior liquid layer could come on four flybys of Titan (two at periapsis and two at apoapsis) by Cassini designed to look at Titan's interior through the Doppler shift in Cassini's signal as it flys by. The non-detection of non-radiogenic Argon (mass=38) suggests that Titan did not get its nitrogen from molecular nitrogen locked into Titan's ices since Argon-38, which has about the same volatility as molecular nitrogen, would condense at a rate proportional to the relative abundance of Nitrogen and Argon in the solar nebular (~10x). Since, the abundance is much less than the 1-10% this condensation should give, nitrogen could not have come to Titan as N2. Instead, ammonia likely condensed with the water ice, and was later brought to the surface. Once ammonia was in an atmosphere, sunlight broke up the nitrogen and the hydrogen, with the nitrogen remaining and the hydrogen escaping into space. RADAR SAR data from October showed evidence for cryovolcanic flows and Venusian-style pancake domes, indicating recent volcanic activity. This would be supported by the possibility of a present liquid layer and would likely be composed of Water and Ammonia, since the ammonia would give the water the bouyancy it needs to reach the surface and would give the right mobility to match the RADAR observations, so that it resembles basalt. Cryovolcanism (or venting at least) is supported by the INMS (an instrument on Cassini) and GCMS measurements of Argon-40, a by-product of the radioisotope Potassium-40.
That's it for now from that talk. A lot of information given. The link above goes to the Real Player stream of the lecture so that you can watch it for yourself.

UPDATE 03/25/05: The talk now appears to be offline. You can find edited transcripts of the talk on the Astrobiology Magazine website.

Wind Speeds on Titan

The Cosmic Mirror is reporting that the Doppler Wind Experiment team for Huygens has already begun to analyze the doppler data retrieved by ground-based radio telescopes like Green Bank to make up for the loss of Channel A. From a talk Mike Bird gave at the University of Bonn on Monday, the winds at 50 km in altitude, or 10 km above the tropopause, were blowing out of the west 40-50 meters/second. Winds decreased with altitude until it was only a few meters per second at the surface. This is consistent with the DISR view of the winds. Marty Tomasko reported in a press conference the day after landing that the winds between 10 and 20 kilometers altitude were out of the west at 7 m/s.

Doppler data also showed the ride higher up in Titan's atmosphere was quite bumpy (more on this in a post later today).

New Tethys Image: Dawn for Odysseus

This new view of Tethys was taken last month and has a resolution of 10 km/pixel (as opposed to imaging from October at 2.5 km/pixel). This view clearly shows the albedo asymmetry on Tethys.

Tuesday, January 25, 2005

Tonight Show Titan Joke

Though of poor quality, Jay Leno during his monologue tonight made a joke about the recent Huygens landing on Titan:

A probe recently landed on the surface of Saturn's moon Titan, finding rivers and clouds made of liquid methane...or it landed in New Jersey.

The Titanese Times

Now that I am hoping to regularly update this blog, I have changed the title and the layout to look a bit more professional. Obviously the title is meant to convey a newspaper-style format, though being participant in some of the news will make it a bit difficult to publish scoops or information not posted elsewhere but perhaps I can add my own perspective to the satellite news of the day.

On the use of Titanese: it has been rather difficult to come up with a suitable adjectival form for Titan. Titanian would be the obvious first choice, but that could become easily confused with the adjectival form for the Uranian moon Titania. Titanic has become a favored form for some ISS team members, but it is unsuitable for me since it just brings to mind a very BAD movie. Titanese is also a possibility, though the -ese suffix is usually limited to nationalities from east Asia (Vietnamese, Chinese, Japanese, etc.). However, given the unsuitability of the first two, I am forced to concede to Titanese. If anyone has any other suggestions, don't hesitate to send me an email.

As stated in the intro, I will strive to continue to post on this blog for news primarily for Titan and Io, though I can't ignore the other satellites, except Europa, that moon will get no press here. Why? Because I feel like it. This blog will also not cover Mars, because it is not an outer planetary satellite and it gets enough press elsewhere. I will also post on the other Saturnian satellites as new results come in and are published. I may occasionally sway to other topics, like politics, but given the current political climate, I may try to avoid that. We'll see.

In terms of contributions, I will obviously look at them and post them as I see fit. Since this blog has a fairly small audience, I don't think an additional author is needed, but if you want to offer your services, I'll look into a dual author or team authorship arrangement, however I'd rather not have a site run by committee.

I'm going to sign off for now though later today, I hope to publish my thoughts on the recent Huygens images. Titan certainly looks like a very interesting place that continues to astound, amaze, and confuse.

Five Questions for Carolyn Porco

The folks at the IRC channel #space on have been given an opportunity to ask five questions of ISS team leader, Carolyn Porco. They are currently taking suggestions for questions and the five best questions will be sent to Carolyn to be answered in the next few months. The DISR team on Huygens has a bit more formal setup on their team homepage, allowing readers to ask questions of team members. I can only think the ability to ask questions of those working on space missions is a good thing, given that reporters at press conferences might not always ask the right questions or the answers given are directed to a more general audience than the average space enthusiast.

NASA To Use Outer Planets Data Analysis Funds for Other Purposes

Keith Cowing over at has a disturbing article indicating that funds previously allocated for Outer Planets Data Analysis have been diverted to other priorities within the agency. This will be a severe detriment to those working on Galileo data analysis which is particularly important for Io since its data came late in the mission. Hopefully the funding will be restored for Fiscal Year 2006.

Titan Rainmaker

Here is the other part of Astrobiology Magazine's interview with Anthony DelGenio regarding rainfall on Titan. So far these interviews have been very nice, given additional perspectives to the Huygens probe findings.

MoonLander: Let it rain

Anthony DelGenio, an ISS team member, talks with Astrobiology Magazine about his thoughts on the recent Huygens landing on

More Spacedaily articles

The Astrobiology Magazine interview with Toby Owens linked below was the final part of a three part interview published last week. Here are the links to the first two parts.

Part 1: Targeting Titan
Part 2: Methane World

Monday, January 24, 2005

Keck observations of Titan

Keck image of Titan from last Thursday, January 20 showing a relatively cloud-free day over the trailing hemisphere of Titan. The filter used for this image cover the methane window at 2.05 microns.

Unbeknownst to me until last week, the Keck telescope in Hawaii has been making regular obervations of Titan this observing season like they did last year. New this year is the emergence of mid-summer southern mid-latitude clouds, also seen by Cassini and Roe et al. starting late 2003. Polar clouds are still seen this observing season, though seamingly larger and more sporatic than last year. Only time will tell whether clouds will be seen at lower latitudes, like near the Huygens landing site as Titan approaches Equinox in 2009.

Huygens lands on Titan

Last Friday, ESA's Huygens spacecraft landed on the surface of Titan around 10.5 South, 192 West, revealing a landscape modified by the flow of methane on the surface, though at the time of landing, liquid methane was at least 15 cm below the surface, as well as tectonism. I will be posting more comments on the Huygens images tomorrow. In the meantime, here are some good links:

ESA Cassini-Huygens Homepage
Descent Imager and Spectral Radiometer Homepage
Amateur Huygens Image Processing

Titan: A Living World? posted an article on Friday of an Astrobiology Magazine interview with the University of Hawaii's Toby Owens, an atmospheric interdisciplinary scientist for the Huygens Team. The interview covers the remote possibility of life on Titan.

New Test of Vagablog

I hope to start editing my blog again now that Huygens has landed.