Friday, April 22, 2005

INMS Results from T5

At an altitude of 1025 km, last week's Titan flyby was the closest yet. The prime instrument at closest approach was the Ion and Neutral Mass Spectrometer (INMS) instrument, which studies the chemical makeup of Titan's upper atmosphere. Despite expectations of find a relatively simple chemistry at those high altitudes, INMS found a plethora of ion species in Titan's upper atmosphere, as far up as the detection limit of 100 daltons (~amu). The periodic nature seen in the ionospheric mass spectra plot above shows that much of the chemistry is dominated by Carbon and nitrogen molecules with multiple carbon atoms. For example, the peak at mass 91 is likely C7H7 or Benzyl and the peak at mass 79 is C6H6 or benzene.
Confused by the graph? Here's a primer on the dalton and its close cousin, the Unified Atomic mass unit (u or amu). Don't become too fixated on the absolute number provided by the vertical scale. Those maybe off, but the relative abundances between masses should be accurate.

New Titan Image: Cassini's Views of Titan

CICLOPS has released three global views of Titan taken during last week's flyby. Each view shows views of Titan taken through various filters. The first view shows Titan in nearly true color, using the Red, Green, and Violet filters on the wide angle camera. Light returned in these wavelengths is dominated by scattered light from the high-altitude haze layers in Titan's stratosphere. The hydrocarbons in these haze layers gives Titan its orange cast at visible wavelengths. The second view use a sum of several CB3 filter (938 nanometer) images. This is the best filter for observing Titan's surface. Brightness variations in this filter are due solely to albedo variations on the surface, with little to no contribution from topographic shading, thanks to the effectiveness of the haze layer to scatter light, even if it allows light at that wavelength to pass through. The final view, also shown above, combines a violet filter image (shown as blue, shows high-altitude hazes), a CB3 filter image (shown as green, shows surface), and an MT3 filter image (shown as red, shows the strong methane absorbtion of Titan's stratosphere).

These images were taken from a distance of 170,000 km from Titan and have a pixel scale of around 10 kilometers per pixel.

More processed images from the T5 flyby will be available next week.

Titan Resurfacing through Biothermal Energy?

Linked above is a paper brought to my attention yesterday. In this paper by Dirk Schulze-Makuch and David H. Grinspoon, the authors suggest that heating produced by organisms near Titan's surface could explain the relatively youthful surface of Titan. Their contention is that organisms could have evolved in hot springs and in temporary crater H2O lakes, and later may have evolved to survive on Titan's surface, metabolizing photochemically produced acetylene. The heat from chemical reactions produced by the organisms, the authors posit, could then be enough to produce the energy needed for the cryovolcanism observed by RADAR.

Personally, I feel there are a number of problems with the arguments in this paper. First, the environments suggested for the development of life are fairly limited in extent but yet the authors require life to be fairly widespread for their heating mechanism to work. They get around this by suggesting the life could have evolved to survive the surrounding terrain, but I would think that much of the energy it produced would go toward not just running the reactions that keep it going, but to also keep the water in its body from freezing. I can buy the alternative metabolic pathways argument just based on the diversity seen on Earth, but the requirement to keep its body from freezing, let alone have enough excess heat to power volcanoes, seems to be a brick wall for life to overcome.

Cassini Significant Events for 04/14/05 - 04/20/05

JPL has posted online their weekly status update for the last week. Nothing really news worthy. The post T5 burn, OTM-23 was cancelled as it was seen as unneeded. The update also provides a pretty good review of activities preformed during the T5 flyby, though I have no idea where they got "Eighteen hours before closest approach there is an outreach image opportunity of Saturn rise/set over Dione" and "this will be first good look ISS has had at the quasi-circular ~1000 km diameter feature, perhaps associated with an impact structure".

This update has started to show up on some email lists though apparently not yet on the JPL website. So if you get an error page, try again later in the day.

New Tethys Image: North and South on Tethys

CICLOPS has released this great, medium resolution view of Tethys taken a few hours after closest approach during the Tethys non-targeted encounter last month. The view shows a region of Tethys south and east of Odysseus basin. What is noticable geologically is the dichonomy between the heavily crater northern terrain and the less cratered plains to the south. In addition, the craters in this more sparcely crater region appear to be filled in and subdued, suggesting increased viscous relaxation in this area, perhaps due to a higher heat flow in this region.

The image was taken from a distance of 200,000 km and has a resolution of about 1 km/pixel, making it one of the better images taken so far of this satellite.

Names for Jovian Moons Discovered in 2002 and 2003

Don't often report on non-Cassini related news, but this is after all, a blog that is just Saturn-centric. Anyways, small discovered around Jupiter in 2002 and 2003 now have names to go with those small, faint dots. The IAU Working Group for Planetary Satellite Nomenclature (WGPSN), in an announcement published in IAU Circular #8502 and now on the discoverers' website on Jovian Satellites, have released these new names:

Jupiter XXXIX Hegemone = S/2003 J 8
Jupiter XL Mneme = S/2003 J 21
Jupiter XLI Aoede = S/2003 J 7
Jupiter XLII Thelxinoe = S/2003 J 22
Jupiter XLIII Arche = S/2002 J 1
Jupiter XLIV Kallichore = S/2003 J 11
Jupiter XLV Helike = S/2003 J 6
Jupiter XLVI Carpo = S/2003 J 20
Jupiter XLVII Eukelade = S/2003 J 1
Jupiter XLVIII Cyllene = S/2003 J 13

The website also contains a list of all currently known Jovian satellites, including those moons discovered in 2003 that do not yet have a name (likely due to insufficient knowledge of their orbits).

The links for each moon take you to their respective Wikipedia article. The standard fare really since not much is known about these tiny satellites, though the discussion of the Kozai Effect and Carpo is pretty interesting.

Thursday, April 21, 2005

New Tethys Image: Banded Moon

CICLOPS has released this low resolution view of Tethys. This image highlights albedo variations seen on the surface of this satellite particularly seen at infrared wavelengths. This image was taken last month a few days after the first non-targeted encounter of Tethys and has a resolution of 8 km/pixel.

Update 04/22/2005 12:00pm - Found a great Voyager 1 image showing this dark band. According to the caption for that image:
The exact cause for the dark band is unknown, but a possible interpretation comes from recent Galileo images of Jupiter's moons Ganymede and Callisto. Both satellites exhibit light polar caps that are made from bright ice deposits on pole-facing slopes of craters. From a distance the caps appear brighter due to a haze caused by thousands of unresolved patches of ice in small craters. The dark band on Tethys may have been formed in a similar manner, consisting of hazy polar caps of unresolved bright ice patches with a dark zone in-between.

Wednesday, April 20, 2005

Planetary Society: The Titan "H" Up Close

The Planetary Society posted an article last Friday summing up our imaging results from T4. Again , a nice article all around.

JPL Moons Page

JPL now has a page on their Cassini website dedicated to the science related to the 34 moons of Saturn. Basically you can click on a moon, see a list of science goals, flybys, and images taken so far for that moon. Still a work in progress, like no individual goals for each moon, no inclusion of non-targeted flybys in the list of encounters, etc. But still might be worth a visit for those who would like a primer on the Saturnian system.

Tuesday, April 19, 2005

New Rhea Image: Dark Patch

CICLOPS has released this view of Rhea's sub-Saturnian hemisphere taken last month. This low resolution view taken in the UV3 filter reveals a darkish patch on the trailing hemisphere (eastern part of this view) first seen by Voyager and was shown in a higher resolution color view a few months ago.

Monday, April 18, 2005

T5 Raw Images

T05 Raw images have started to trickle into the JPL Raw images page. Still waiting for more, but here are the early highlights:
UPDATE 04/18/2005 10:30am: CICLOPS has posted some additional raw images on their website:

New Cassini Image: Sister Moons

Today's Daily release from CICLOPS shows both Dione and Tethys in the same narrow angle field of view. From the caption:
Extensive systems of bright fractures carve the surface of Dione (1,118 kilometers, 695 miles across). The double-pronged feature Carthage Linea points toward the crater Turnus at the 9 o’clock position near the terminator, and Palatine Linea runs toward the moon’s bottom limb near the 5 o’clock position.

In contrast, the surface of Tethys (1,071 kilometers, 665 miles across) appears brighter and more heavily cratered. The large crater Penelope is near the eastern limb. The huge rift zone Ithaca Chasma, which is 3 to 5 kilometers (2 to 3 miles) deep and extends for about 2,000 kilometers (1,200 miles) from north to south across Tethys, is hidden in shadow just beyond the terminator. For comparison, the Grand Canyon in Arizona is about 1.5 kilometers (1 mile) deep, and about 450 kilometers (280 miles) long.
This image was taken last month and the resolution on these two moons varies from 9-10 km/pixel.

Large Surface Coverage Huygens Mosaic

Rene Pascal has updated his Large scale Huygens mosaic created using the raw images posted on the web. What makes his contribution unique are the photometric corrections he applies to each image to remove the effects of camera artifacts as well as including images from higher altitude. Certainly worth a look.