In regards to the channels cut in this crater that might suggest infill, see the second image on this page that shows the same thing can happen in maars:

Coliseum Maar, Hopi Buttes, Arizona
http://volcano.und.nodak.edu/vwdocs/volc_images/north_america/coliseum_maar.html

This image also shows that maars can have raised rims, as can impact craters. So this feature alone can not be used to identify the craters seen on Mars as impact craters.

This page is nice in that it gives both the gas release and water interaction explanations for the origin of maars.

You can find alot by searching the net. Try google.com under "maars" and "Mars." Google is nice in that it also searches and presents PDF files such as those presented at recent LPSC conferences.

Bob Clark