Hmmm, I'm looking at the first HiRise image at:

http://photojournal.jpl.nasa.gov/jpeg/PIA08061.jpg


Does anyone else notice the unusual distribution of what appear to be
craters?

I haven't looked at this statistically, but it appears that the
"craters" are clustered very close together in some cases -- more so
that an a random distribution would indicate. Could be that I see
color differences as well.

Here's my wild explaination: These crater clusters are volcanic or
thermal vents -- not impact craters.

Comments?