[X] My Assistant

[jmknapp]

Tried a "true color" version of the trench, using L2, L3, L4, L5, L6, L7:



Full Res version

[djellison]

Good stuff. Looks like they did a third image of that set - if you can do that one as well, I'll put them thru PTGui and whack a properly stitched pan out of it if you like

Doug

[jmknapp]

Will do Doug, but just checked & it looks like there are still quite a few drop-outs on the third images? So I'll wait for that to be rectified.

[Gray]

Fantastic image. Space.com reports that Gilbert Levin, a Viking Lander investigator, claims that the reflective material at the bottom of the trench is ice.

[lars_J]

Space.com reports that Gilbert Levin, a Viking Lander investigator, claims that the reflective material at the bottom of the trench is ice.

Uh-huh. Sure.

[jmknapp]

The brilliant white does appear to be just a reflective veneer. Note the wheel cleats punch right through it to the red areas below, so it's not just coincidentally the start of a thick layer of whitish material.

So if not ice, what? CO2 ice?

[tdemko]

gypsum? anhydrite? bizarre Martian chlorides or sulfates?

[jmknapp]

Maybe so.

However, this paper on life in an acidic martian "snowbank" was written by Benton C. Clark, an astrobiologist who is one of the selected panelists for the press conference in DC tomorrow!

http://www.lpi.usra.edu/meetings/sixthmars2003/pdf/3106.pdf

[tdemko]

Joe:

That paper came out as a possible explanation for the "active" gullies seen on some steep slopes in Martian craters and along some cliffs. Both Spirit and Opportunity have landed in flat places, and I wouldn't think that these snowbanks could last as long as they might in a partially shaded crater wall/cliff area. In fact, I read in other sources that the "snowbank theory" supporters think they might form during times in the 10-100K year Martian orbital cycles when the atmosphere may be denser and contain more moisture (polar caps melted/sublimated away) and may survive into times of dryer/less dense conditions by mixing and mantling with dust.

However, it is interesting that the author calls upon some sulfate soil chemistry to explain things in non-ice areas. This may be what is going on in places like 'Laguna Hollow".

[jmknapp]

Just to clarify, he uses the term "snowbank" as a catch-all for "atmospheric precipitation (snow); surface adsorption; clathrate formation; upward percolation of H2O vapor or wicking of liquid created by subsurface heat sources; or deflation
of overburden to expose buried ice or ice-rich permafrost (for purposes of expediency, such surfaceexposed deposits will be referred to in this paper as
'snowbanks,' regardless of the source or mechanism of transport of H2O to the surface)."

If there is water at the surface at Meridiani, then presumably it is coming from a subterranean source, rather than atmospheric frost, etc., and so would be continually replenished in that way.