[ispom]

do you remember ?

a deep hole was found on Mars

http://www.space.com/scienceastronomy/070605_mars_hole.html

now there is a new view of the Dark Pit on Arsia Mons !

http://www.2-0.scienceticker.info/wp-content/uploads/2007/08/mars-hirise-loch.jpghttp://hirise.lpl.arizona.edu/PSP_004847_1745

From the shadow of the rim cast onto the wall of the pit we can calculate that the pit is at least 78 meters deep,
presumably an “einsturzkrater”
(can’t translate, sorry) perhaps: a crater originated by collapsing of the surface

and now:
more entrances to caves along the slope of a Martian volcano discovered,
now we know 7 such holes

http://www.jpl.nasa.gov/news/news.cfm?release=2007-106