XPost: sci.astro, alt.sci.planetary, sci.geo.geology   
   From: g_d_pusch_remove_underscores@xnet.com   
      
   mlm  writes:   
      
   > In 1 of the 3 DIMES images taken by Opportunity on its approach to the   
   > surface (at 1404m), there is a brightly ringed crater and a distinct,   
   > slightly diffuse dark circular shadow about half a crater width to its   
   > left.  Is this the shadow of the spacecraft?   
      
   Highly unlikely, since this photo is almost certainly being taken from a   
   quite high altitude, and your alleged "shadow" is a substantial fraction   
   of the large crater's diameter --- whereas even the lander's parachute   
   is quite small compared to the diameter of a typical aregraphical feature !!!   
      
   Downloading the image and tweaking the image's intensity curve using the   
   image editing tool 'xv' clearly brings out an ejecta blanket surrounding   
   your dark spot, and gradations in intensity within said spot, that strongly   
   suggest to me that your "shadow" is merely a deep, relatively "fresh" crater,   
   and that the limited contrast range of a typical color monitor simply can't   
   easily display the full dynamic contrast range in this image.   
      
   Once this image has been processed a bit to "dodge out" the "over-exposed"   
   crater rim and "burn in" the darker regions away from the main crater   
   and within the dark, deep crater you've noticed, this picture will become   
   MUCH more photogenic, and the nature of its various features quite obvious.   
      
      
   -- Gordon D. Pusch   
      
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