But one of the issues on Mars is the scale. Everything of the sort is an order of magnitude (or more) larger on Mars than on the Earth. How come?

Also, have you seen the appearance of polar areas "defrosting?" Look at this example:

http://ida.wr.usgs.gov/fullres/divided/m10014/m1001405a.jpg

from: http://ida.wr.usgs.gov/html/m10014/m1001405.html

The pattern of tiny ridges between the black spots is nearly identical to the cracking on the Nilosyrtis surface. Maybe a similar process is involved... Doesn't necessarily involve mud. But I can't figure out what would be going on instead. Maybe Nick can come up with something.

The rubbly surface in Nilosyrtis reminds me of lava erupted in cold water or ice. If that's what happened, then the cracked surface in Nilosyrtis (but not the similar appearing surface near the south pole) could well be the remnant of a now evaporated sea...

And since all the surfaces in Nilosyrtis look darned fresh, I'd bet whatever caused the rubbly region, the "shoreline," and the "cracked mud" did not occur billions and billions of years ago.

Cheers, B R Felix