Deep Hole Found on Mars

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

The geological oddity measures some 330 feet (100 meters) across and is located on an otherwise bright dusty lava plain to the northeast of Arsia Mons, one of the four giant Tharsis volcanoes on the red planet.

The hole might be the sort of place that could support life or serve as a habitat for future astronauts, researchers speculated.

HiRISE image specialists said the pit must be very deep to prevent detection of the floor from natural daylight, which is quite bright on Mars.