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New Marsis News
Guest_BruceMoomaw_*
post Dec 19 2005, 01:32 AM
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You wanted it, you got it. Here's the additional stuff revealed by Jeffrey Plaut in his AGU talk:

(1) The team is seeing tentative evidence of several more buried, ice-filled craters beneath the northern plains -- which, as he said, are starting to look like a major reservoir of Martian water. (It's fairly easy, I think, to see how these things were created: they started as water-filled crater lakes, built up an insulating lag deposit on top as they sublimated -- as well as having more dust blown in on top of them -- and then, having had their ice supplies thus sealed off from further sublimation, simply got covered up later by whatever processes filled in the northern plains.)

(2) There is still no evidence as yet (although they're still looking) of a meltwater layer underneath that portion of the northern layered deposit that MARSIS examined. The biggest indicator is that the reflectivity of the surface underneath the layered deposit does not rise at any point in the profile above that of the bare ground beyond the edge of the layered deposit -- whereas, if there was meltwater tucked in under the layered deposit, one would expect the reflectivity of that underlying layer to rise sharply at some point when you get in some distance underneath the main body of the layered deposit.

(3) The lack of visible crustal sagging underneath the weight of the layered deposit indicates that Mars' rigid lithosphere is at least 150 km thick at that spot.

(4) Unfortunately, due to the delay in getting MARSIS started, this will be the only profile it does of the northern layered deposits unless there's a very long-term extended mission. However, it has now begun acquiring fully 200 profiles of the southern layered deposits over the next few months -- and Plaut presented the first few of those. They show the southern LD to be considerably thicker -- 3 km -- and while again there is no obvious sign yet of a meltwater layer, there are at least two very clearly distinguishable thick sublayers within the southern LD. (And, again, no sign of crustal sagging under the LD.)

(5) In spring 2006, MARSIS will view the first places -- other than beneath the polar caps -- where it's thought likely that there might be a liquid water layer within its depth range. These are the warmer areas at lower latitudes, particularly the Hellas and Argyre Basins.

(6) The single most important discovery, as Plaut says, is simply that "the thing works" -- our fears that Mars' iron-rich crust might block the signal have been totally disproven. I wonder how well SHARAD's shorter-wavelength profiling will go?

(7) In that connection, and to answer a question asked by "Harder": the confusion produced by echoes off the rough surface prevents MARSIS from getting a meaningful profile of the top 200 meters or so beneath the surface. Over to SHARAD for that.
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JonClarke
post Dec 19 2005, 03:10 AM
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QUOTE (BruceMoomaw @ Dec 19 2005, 01:32 AM)
You wanted it, you got it.  Here's the additional stuff revealed by Jeffrey Plaut in his AGU talk:
*


Thank you!!!!!!! Any idea when and where this will be published?

Jon
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Guest_BruceMoomaw_*
post Dec 19 2005, 03:28 AM
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Nope. I imagine the ESA site will be the first one out with it.
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edstrick
post Dec 19 2005, 07:06 AM
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It is possible that if there is slow melting at the base of the polar ice deposits, as Steve Clifford suggested back in the 80's, it could percolate down to the water table kilometers down. Detection of damp soil at the base of the deposits, especially if it's had salts progressively washed out down to deeper layers, might be much more problematic than detecting a water table or saturated zone below the cap. Dunno the quantative numbers that might back up the above arm-wave, though.
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lyford
post Dec 19 2005, 09:17 PM
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thank you thank you thank you thank you [break]


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Lyford Rome
"Zis is not nuts, zis is super-nuts!" Mathematician Richard Courant on viewing an Orion test
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edstrick
post Dec 20 2005, 09:13 AM
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Note: The fact that the layered polar ice and dust deposits are so non-absorbing -- implying they're 98% ice and maybe 2% dust -- suggests that the short wavelength instrument on Mars Recon Orbiter may be able to sound the entire ice cap depth, rather than a few hundred meters.
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peter59
post Dec 13 2010, 03:51 PM
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I found a directory with many hundrets MARSIS radiograms.
ftp://psa.esac.esa.int/pub/mirror/MARS-EX...-TEC-EXT1-V1.0/
Typical radiogram looks like this:
Attached Image

or this:
Attached Image

Does anyone know how to interpret them?


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Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html
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