Massive Subsurface Ice Deposits in Southern Hemisphere, MARSIS results - LPSC 2006 Options

[Guest_paulanderson_*]

Thanks to Doug for pointing out this LPSC update:

Mars Express: Probing the Depths
ftp://ftp.lpi.usra.edu/pub/outgoing/lpsc2006/full102.pdf

Another good article:

Martian Ice: Wide and Deep
http://skyandtelescope.com/news/article_1695_1.asp

"More recently, a shift in Mars Express's orbit has allowed MARSIS to probe the planet's south pole. There the buried ice extends down to 3½ kilometers (2 miles) under the cap in some places. Water ice appears quite transparent at radar wavelengths, and the ease with which MARSIS's signal penetrates the polar terrain suggests that the ice is relatively pure. "There's at most only a few percent of impurities," team coleader Jeffrey Plaut (Jet Propulsion Laboratory) told planetary scientists meeting in Houston this week.

Potentially more exciting is MARSIS's discovery that huge quantities of ice may underlie a large plain beyond the southern cap called Dorsa Argentea, which covers 3 million square kilometers, about 2% of the planet's surface. Geologists originally thought Dorsa Argentea was a volcanic plain, but James W. Head III (Brown University) and others recently realized that a broad ice sheet must lie beneath its dusty surface. Plaut reported that MARSIS has found multiple layers stacked beneath Dorsa Argentea to depths of up to 500 meters — and if they’re all ice, they represent a reservoir large enough to cover the entire planet with water to a depth of about 10 meters (30 feet)."

[edstrick]

Water that's essentially frozen, or combined as hydrate in rocks like the Meridiani and Gusev evaporite and salt deposits is probably widely distributed on Mars, but harder than <deleted> to detect directly. One of the things that Marsis is looking for but I suspect is not seeing is a transition between the cryo-lithosphere <frozen megaregolith> and a mid-crustal water-table, kept warm by geo-<aero->thermal heat flow. I think the overall suspician pre-mission is that it wouild be too deep and too attenuated by iron-rich rock absorption of the radiowaves to be detected.

Future missions might carry a super-Marsis payload... more complex antennas giving a more directional vertical beam, much more radiated power.. more antenna/receiver sensitivity.... Not trivial. Longer wavelengths might help probe deeper., but at the expense of horiffically long antenna, difficulty with even the nighttime atmosphere, and lower vertical resolution.