In response to Marcia's post at
http://www.habitablezone.com/space/messages/22444.html

where she wrote:
Aside: Hellas is the general area where MOLA found the 'echoes' or leftover traces of the Martian magnetosphere.

Alex writes:
A couple of points: (1) MAG/ER (not MOLA) returns magnetic data; and (2) MAG/ER results actually indicate that the Hellas impact basin shows no signs of remanent magnetism, though adjacent terrains do. Presumably, under current accretionary theory Hellas was formed by an impactor in the very, very early stages of proto-Mars' formation (early or pre-Noachian). Calculations show that the impact shock forces probably melted the crust at that locale above the Curie point and destroyed any fossil magnetism. If so, it is certainly plausible to reason that Hellas postdates the formation of the magnetic striping. To be sure, it is true that our knowledge of absolute dates in Mars' history (especially the early Noachian) is poorly constrained; however, positing that Mars' global magnetic dynamo ceased operation with 500 Myr of core accretion is a sound hypothesis.

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In response to the thread below named "MGS management," a couple of observations. As has been pointed out by others, including myself earlier at:

http://www.habitablezone.com/space/messages/22094.html

MOC, specifically the Wide Angle system, is only capable of mapping the Martian surface (~1 km resolution) in two colors, which was the goal of Science Campaign B in August 1999. As for data return, AFAIK there are no "foreign" antennas that provide more capability than the DSN 34m net. Undoubtedly, more 70m time would be an improvement, but according to MGS people with whom I spoke yesterday, the returned volumes would be increased "only by a factor of 3-4." To be sure, this is nothing to sneeze at; however, IMO it is not really a revolutionary leap.

Alex R. Blackwell
University of Hawaii