New images of deep Martian caves

untree writes: The Astronomy Picture of the Day today is an image recently taken by the HiRISE instrument on the Mars Reconnaissance Orbiter. More information is available on the Planetary Society blog, including a description of the paper (pdf) that describes this series of caves.

From the image description:

"Black spots have been discovered on Mars that are so dark that nothing inside can be seen. Quite possibly, the spots are entrances to deep underground caves capable of protecting Martian life, were it to exist."

And for fans of traditional units of measure, this cave entrance is about the size of a football field.