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Posted by: AlexBlackwell Sep 14 2006, 01:09 AM

Caitlin Griffith et al. have a real interesting http://www.abstractsonline.com/viewer/viewAbstract.asp?CKey={CA030768-323C-47DD-A852-E2F04DEF93FC}&MKey={66F0352A-30DC-4B9F-B0CC-E851495B78DC}&AKey={AAF9AABA-B0FF-4235-8AEC-74F22FC76386}&SKey={AAAA5F48-F7FC-4FEC-9BDF-5E651C22B122} for the upcoming DPS meeting.

Posted by: ngunn Sep 14 2006, 10:34 AM

This abstract appears quoted in full along with a comment from Bruce Moomaw in John Sheff's post no. 3 of the 'Interesting Titan stuff . . ' thread below. It seems we are in for a feast of new Titan insights and new Titan mysteries soon.

Posted by: AlexBlackwell Sep 14 2006, 04:20 PM

Well, well. Whaddya know

From the http://www.sciencemag.org/content/vol313/issue5793/index.dtl:

Evidence for a Polar Ethane Cloud on Titan
C. A. Griffith et al.
Science 313, 1620-1622 (2006)
http://www.sciencemag.org/cgi/content/abstract/313/5793/1620

See also the accompanying Perspectives piece in the same issue:

Titan's Polar Weather
F. M. Flasar
Science 313, 1582-1583 (2006)
http://www.sciencemag.org/cgi/content/summary/313/5793/1582

Note that the specific links to the Griffith et al. paper and the Flasar article will not go active until the embargo is lifted in a few hours.

Posted by: volcanopele Sep 14 2006, 05:04 PM

The paper (and abstract) won't be available until around 1pm PDT.

Posted by: volcanopele Sep 14 2006, 06:44 PM

The VIMS team had an image release today showing some processed views of the ethane cloud:

http://photojournal.jpl.nasa.gov/catalog/PIA08739

This releases shows various views taken in late 2004 and 2005 and show the cloud at a wavelength of 2.8 microns.

Posted by: AlexBlackwell Sep 14 2006, 06:46 PM

http://uanews.org/cgi-bin/WebObjects/UANews.woa/7/wa/SRStoryDetails?ArticleID=13053
Lori Stiles
University of Arizona
September 14, 2006

Posted by: WindyT Sep 14 2006, 07:08 PM

When the articles come back after embargo, can someone answer:

is this just a way of proving the liquid at the poles is primarily ethane

or are the cloud accumulations of ethane within that specific region going to be quantified?

Edit to answer
Cassini's VIMS Detects Vast Polar Ethane Cloud on Titan (link above)
Does answer some of my questions, so I guess I'll have to see the article in Science.

Posted by: volcanopele Sep 14 2006, 07:15 PM

VIMS claims to be able to spectrally detect liquid ethane (and liquid methane) IIRC. Of course they would need a good look at a suspected lake first There were able to resolve Ontario Lacus last June, but I don't know what came of that, and that was only a couple of pixels. There is talk of giving VIMS a chance at having a great look at Ontario Lacus in T38 (or T39) when we basically fly right over it, but that would require trading with RADAR. And, obviously, the north polar lakes found by RADAR are out of the question until 2008, 2009 at the earliest due to the current illumination situation.

For the second question, are you asking if they can tell how much ethane is in the clouds?

Posted by: AlexBlackwell Sep 14 2006, 08:50 PM

The links are active now.

Posted by: volcanopele Sep 14 2006, 09:11 PM

Interesting article. They explain why ISS doesn't see the cloud (the optical is low enough enough that you can't distinguish it from lower opacity due to haze). They also say that one couldn't confirm ethane ice at the poles from spectra alone, since methane and ethane ice spectra are indistinguishable from each using VIMS; analysis of geomorphology would be needed.

Posted by: WindyT Sep 15 2006, 04:44 AM

Yes.
However, I can wait on that -- as from what I understand, there's a mystery as to why there's not more ethane than there is. So, I'm guessing that all the volumetrics of cloud content will have to be run. I'll sit back and wait for more info.

Posted by: mars loon Sep 16 2006, 11:45 PM

A report from Spaceflightnow.com

http://www.spaceflightnow.com/cassini/060914titancloud.html

Vast polar ethane cloud detected on Saturn moon
UNIVERSITY OF ARIZONA NEWS RELEASE
Posted: September 14, 2006

Cassini's Visual and Infrared Mapping Spectrometer (VIMS) has detected what appears to be a massive ethane cloud surrounding Titan's north pole. The cloud might be snowing ethane snowflakes into methane lakes below.

The cloud may be the clue needed in solving a puzzle that has confounded scientists who so far have seen little evidence of a veil of ethane clouds and surface liquids originally thought extensive enough to cover the entire surface of Titan with a 300-meter-deep ocean.

Posted by: Julius Sep 17 2006, 02:57 PM

Could someone kindly explain the relations between supersaturation of Titan atmosphere,cloud formation and precipitation.

Posted by: remcook Sep 18 2006, 11:49 AM

OK, this is how I understand it:

In general, condensation occurs when a certain gas has a higher concentration than its saturation level. This saturation level is dependent on temperature and pressure and the gas properties. Besides this, there should be consensation nuclei on which the gas can condense. In Titan's case these are mostly the aerosols.

The idea of methane supersaturation in the troposphere comes from the fact that large concentrations of methane (above its saturation level) are required to fit far-infrared Voyager data. If this is true, a lack of condensation sites or something more complicated is make condensation impossible there. Huygens also found methane values close to saturation.

There seem to be a range of different clouds on Titan. Firstly there are the mid-latitude clouds. Complex computer models of Titan's atmosphere show that there is rising 'air' in the troposphere at these latitudes, which brings enriched air higher up. There, it is colder and the methane will pass its condensation level and condense if there are condensation nuclei. Because the methane in the high troposphere are close to condensation anyway, once condensation starts droplets grow very quickly and fall quickly downwards, making the clouds changing rapidly. Whether this is the real process behind the mid-latitude clouds is not sure. These clouds tend to form preferably at specific longitudes, making some people believe cryovolcanism is bringing extra methane there, causing the clouds.

Then there is the big South Polar cloud. The same Titan model predicts these as caused by a circulation cell there.

Then a range of gases condense in the North Polar stratosphere. The mean circulation on Titan right now goes from pole to pole: air is brought up from the south and descends at the north. On Titan, most gases are produced high in the atmosphere, and so there is more of it the higher you go. Now, the downward motion brings air from high altitudes, which thus is enriched in gases, down to colder levels lower down. This causes condensation as well. It's absurdly ocld in the north anyway, which makes things even worse. The ethane cloud discussed in this topic is one of this category.

Hope this is clear. Sorry for the long post.