[X] My Assistant

[Guest_BruceMoomaw_*]

(1) The Jan. 2005 "Geochemical News" ( http://geochemsoc.org/archives/gn/gn122.pdf , pg. 9-16) contains an interview with David Des Marais full of intriguing statements of his views on both Mars exploration in particular, and the difficulties of interpreting possible Precambrian fossil evidence in general.

(2) MEPAG's Mars Human Precursor Science Steering group -- which issued its report in mid-2005 -- had a subgroup devoted to determining the necessary measurements to allow safe landings and surface exploration by both unmanned and manned craft, and its report is at http://sirius.bu.edu/withers/pppp/original...resentation.ppt . It's particularly interesting for two reasons. First it summarizes the kinds of measurements that must be made by the atmosphere-oriented 2013 Mars Science and Telecom Orbiter for such purposes -- the biggest problem is wind measurements at various altitudes, which may require development of a Doppler lidar. Second, page 8 indicates that the MER landings were even a nearer thing than we thought:

"Spirit designed with range of atmospheric states for during EDL

• A week before entry TES observation of dust storm changed anticipated
atmosphere

• Based on TES, a new density vs altitude profile was created

• However, the reconstructed atmosphere, done post-flight, indicated a
significantly different density (reduced by 15% between 20-30 km) from TES
calculation, and was very close to the limit of system performance

• Also, steadily increasing oscillations of both Spirit and Opportunity before
parachute deployment nearly exceeded safe range (could get tangled chute).

• Oscillations due to either unexpected atmospheric turbulence (some unknown
aerodynamic instability) or mechanical instability of vehicle in fluid.

• Lesson: The atmospheric state is not well quantified, with both models and
NRT calculations yielding weather predictions with large intrinsic errors

• Lack of atmosphere information may affect vehicle design, possibly creating
unstable descent system

• There are still unexpected turbulent layers, and unexpected affects from large
atmospheric dust storms"
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Obviously, we cannot keep running these risks as our landers get bigger and more expensive -- a better understanding of Martian atmospheric behavior and changes is crucial for the immediate future, not just the moderate future.

[djellison]

One of the squillion little projects I'm trying to do is to put together an animation of the MER entry up to the lander seperation event which would hopefully demonstrate the sort of occilation that talks about. Thanks for the headsup on the PPT - interesting reading. Mars really is a nasty planet to land on. Not Titan, not the Moon, just a nasty middle ground.

Doug