[X] My Assistant

[Gray]

Take a look at the rock in the lower right corner of this image:



There appear to be two concentric rings on the face, but they only show up with filters 5 and 6. Any thoughts as to what they might be?

[Marcel]

From my physical geographers point of view, I think there's no reason why spirit should NOT be on the bottom of a former lake. Morphology on a larger scale (from orbital data) suggests it actually does. I can't think of something else but a fluid with sediment when I look at the flatness of this crater floor and the meandering valley towards it. The only other possibility could be instantaneous filling with lava directly after impact (like mare).

However, meteor impacts, wind and mass-movement after chemical and/or physical weathering (to my opinion the major morphological processes that are actually taking place on mars at the rover sites right now) most probable wiped out and/or burried direct evidence of water at the Spirit site. A couple of 100 million years will do.

On the other hand, Meridiani plains seems like a MUCH younger landscape regarding the interaction with water (less craters ?, flatness, berries, cavities and strata (layers) within a meter depth !)

Did Gusev dried up earlier than Meridiani did, so dry processes formed the majority of visible features near Spirit at the moment ? And where did the ejecta at opportunity's site go from the nearby crater(s) ?

How about this: Bonneville is formed after freeze drying of Mars, ejecta lies relatively unchanged (eccept weathering and cavitation by airborn particles). The landingcrater of Opp. however must have formed while Mars was still in a wet period because ejecta simply dissolved, weathered and washed away.......
Could statistical analyses of crater distribution, long term impact frequency (they know al lot about this from craters on the moon, mercury and asteroids) and ejecta appearance add to a more complete reconstruction of happenings ? Or is it allready done ?


Marcel from Holland.