Huygens News Thread, News as and when we find it Options

[Juramike]

Thermodynamically at least, exposed pure water ice should be "attacked" by the atmosphere to form a methane hydrate clathrate rind.

BUT, this clathrate should be spectroscopically identical* to water ice and methane.
* in theory at least, VERY VERY precise IR measurements could detect the teensy IR absorption shifts due to the vibrational constraints of the clathrate cage.

There could be an absorption-desorption/concentration of the surface clathrate rind that causes a concentration of a lag deposit, then a chemical reaction (with atmosphere, or just itself?) - the clathrate beign the agent transferring and concentrating stuff (from down deep?, subsurface flow?, or atmospheric products selectively absorbed/desorbed?).

The low temperature will be a kinetic barrier for any chemical reactions.

-Mike

[ngunn]

Ah! There you are Mike. Any thoughts on the VIMS image itself? To me it looks as though it's displaced the SAR as Cassini's best view of the landing site so far. Is it, and the interpretation in the abstract, in line with your expectations?

[Juramike]

Ah! There you are Mike. Any thoughts on the VIMS image itself? To me it looks as though it's displaced the SAR as Cassini's best view of the landing site so far. Is it, and the interpretation in the abstract, in line with your expectations?

I think the DISR still has the best resolution of the landing site. Hard to beat 30 cm/pixel!

(The T8 and T41 SAR RADAR have resolutions of about 170 m/pixel; according to the abstract, VIMS is about 500 m/pixel.)

Everything seems to sorta fit, the pleasant surprise to me is that the western DISR bright spot (under the Western "R2") and the bright spot just S of the "Spooky Dude" formation (just under the Eastern "R2") are both VIMS Bright unit.

[The bright spot S of the "Spooky Dude" which I'm calling "DISR Bright Mass" is my new favorite feature.]

The Dark Spot of the S Island is just visible at the extreme SE edge of the VIMS image. It is VIMS dark blue unit.

-Mike

[Juramike]

Here's how to make a blink with the VIMS from the abstract and the Huygens Channel combined T8+T41+DISR+ISS mosaic:

1) Download the original version of Huygens Channel Redux w vortex-modified PIA08114 DISR mosaic (256 pix per degree) at the original size (963x1450):
http://www.flickr.com/photos/31678681@N07/...117943/sizes/o/

2) Load into your favorite image processor (I use Photoshop, but Powerpoint should also work)

3) Select and Clip VIMS Figure 1b from the abstract and paste into a new layer in your favorite image processor.

4) Increase size of VIMS Figure 1b 480%, rotate counterclockwise 1 degree.

5) Line 'em up in xy and blink away to your hearts delight!

-Mike

[ngunn]

I think the DISR still has the best resolution of the landing site.

Yeah, but it isn't on Cassini.

[DFortes]

Mike's right about the formation of clathrate by interaction of atmospheric gases with surface ice. It would indeed be very slow, but there are several billions years to do the job. There are a couple of papers which talk about this, some more recent ones by Caroline Thomas, plus the one by John Osegovic, and even a tatty old LPSC abstract by me!

Mike's also right that clathrates and ice are utterly indistinguishable from one another in the near IR. Well, at least on Titan, no thanks to that pesky atmosphere. The enclathrated methane adds absorption features, but they are in the exact same position as the gas phase. Annoyingly, one would be looking through a column of gas containing methane to make such a measurement.
This is a really important first-order question; what is Titan's crust made of? If only there was some way we could find out....

*cough*
http://dx.doi.org/10.1016/j.asr.2008.11.024

[ngunn]

Thanks for that!

I take it from Mike's reply and yours that there is no conceivable way (at least on Titan) to 'de-ice' the surface of a mass of clathrate, or to disguise its spectral signature. We see no ice signature in the spectrum of the bright highlands, yet the assumption persists that that is what they're made of - such a strong assumption that even the design of future instruments is based on it. What's to stop there being a kilometre or two of various types of organic material covering almost all of Titan? What's to stop the highlands being piles of wax? or soap?

[Juramike]

What's to stop the highlands being piles of wax? or soap?

(The real giggle is that Swiss Cheese is consistent with properties of Titans surface: dielectric constant, volume scattering from a porous surface, IR absorbance similarities [some H2O, some organics], and that yellow color, too....)

[ngunn]

Right, so definitely not lemon sorbet then?

[titanicrivers]

VIMS of the landing site here:
http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1599.pdf

In view of the intense interest of a number of us here may I appeal to the authors to post a larger version of the image in Fig.1 of that abstract?

The abstract of and R. Jaumann et. al. and the cogent discussion the above posts are fascinating and educational indeed. Here I Utilized the non-anotated image (Fig 1c) and have layered a slightly enhanced VIMS image to the previous animation of post #560. VIMS is layered in 20% gradient steps in this case. As discussed by juramike and ngunn in post #588, the arrowhead portion of Spooky Dude is apparent as a VIMS bright unit, dunes appear in the brownish VIMS shade and the S 'island'-DISR dark spot in (SE corner) is a VIMS deep blue unit.

[ngunn]

Here I Utilized the non-anotated image (Fig 1c)

Problem is, Fig 1c includes details finer than the VIMS resolution which must therefore come from the underlying DISR image. So unless you've done some fancy subtraction of 1a from 1c I don't think we're looking at that spooky dude in VIMS independently (except through the hole in the 'R' in 1b).

[titanicrivers]

Problem is, Fig 1c includes details finer than the VIMS resolution which must therefore come from the underlying DISR image. So unless you've done some fancy subtraction of 1a from 1c I don't think we're looking at that spooky dude in VIMS independently (except through the hole in the 'R' in 1b).

Agreed. I didn't read the caption closely enough for Fig1c. Have the authors released a Fig1b without the annotation?

[ngunn]

I did ask in post 585 for an un-annotated version. Nothing's been volunteered so far. Maybe it's not reasonable to expect anything more before the conference itself. It's good to know the data exist, though, and someone here could always try that subtraction I mentioned.

[Juramike]

More descent images, based on Keller et al. alignment:

Seconds before Landing (3 m/pixel): http://www.flickr.com/photos/31678681@N07/3262209024/
Huygens Touchdown (3 m/pixel): http://www.flickr.com/photos/31678681@N07/3261385063/

-Mike

[Juramike]

Zoom of the extreme center of the PIA08114 mosaic. This has been cropped, flattened, and enlarged 2.3x and warped slightly.


The image scale is 20 cm/pixel. The entire structure at the center of the image is the size of a modest house (110 m).

Based on Karkoschka et al., Planetary and Space Sci. 55 (2007) 1896-1935. "DISR imaging and the geometry of the descent of the Huygens probe within Titan's atmosphere." (doi: 10.1016/j.psss.2007.04.019) I'm placing the touchdown point of the probe about 3/4 of the way to the north edge from the center of the image.

A full resolution TIFF is available here: http://www.flickr.com/photos/31678681@N07/3274864563/

-Mike