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[Guest_AlexBlackwell_*]

APL-Built Mineral-Mapping Imager Begins Mission at Mars
JHU/APL
For Immediate Release
September 27, 2006

See also A.J.S. Rayl's story at TPS.

EDIT: I changed the topic title because, as I understand it from the press release, the cover was opened, not jettisoned.

This post has been edited by AlexBlackwell: Sep 28 2006, 04:48 PM

[jamescanvin]

Quite a good article from the BBC about this today.

[dburt]

Quite a good article from the BBC about this today.

Well, Richard Kerr has a "damp, but not wet" Mars quote at the end of that BBC article anyway. A bit of a change from his "giant vanished lake or sea" remarks for Meridiani made when Science chose a super-wet Mars as its 2004 "Discovery of the Year". So maybe the pendulum is indeed swinging back towards dryness. Still, I find it curious that the boulders covering the northern plains (and earlier found in abundance at every landing site save Meridiani) have not yet been attributed to impacts, but rather to some sort of floods or glaciers or volcanism. Nevertheless, I see no conceptual problem with northern ocean deposits that later was covered with lava flows and/or impact debris (including boulders), any more than with the putative lake beds in Gusev covered with the possible impact debris we now see there (breccias, plus fines at Home Plate). Who knows, there may even be lake beds deep under Meridiani (although they'd have to be deeper than the bottom of Victoria Crater, apparently). Finally, as Emily noted out last June, there seem to be boulder beds interspersed with some finely layered Meridiani-like beds in MRO images, at least consistent with an impact origin for everything. Orbiters image only the surface, and landers and rovers visit only the surface, so speculation will continue about the subsurface, despite new radar data showing a heavily cratered basement to the smooth Northern Plains.

Regarding the mysterious gullies, the apparent lack of restriction to particular insolation angles indeed suggests they may not be caused by simple melting of surficial snow or ice, but it probably doesn't rule out escape of deep chloride brines, which carry their own antifreeze (also antivapor). The newly reported high slope angle of gullies with light-toned deposits seems difficult to reconcile with a brine flow origin though, or at least the control is not obvious. In contrast, the strict absence of gullies from near the equator suggests some sort of strong climate and ice/melting effect (even if ice is only the rock cement) - it doesn't seem consistent with simple debris flow. At the very least, I imagine it will turn out that not all gullies form by the same mechanism, any more than they do on Earth. The upcoming Martian Gullies workshop being organized by LPI's Allan Treiman (the first person foolish or courageous enough to suggest a dry debris flow or landslide origin for the Mars young gullies, athough he didn't get a citation in the latest MRO Science article) should be of interest to devotees.
http://www.lpi.usra.edu/meetings/gullies20...s2008.1st.shtml

I'll probably end up going, although it's only a month before LPSC.

--HDP Don