Maybe the Martians are tired of their eavesdropping neighbors? Seriously though, this has gaming possibilities. What if an alien race was using Mars as a secret observation post or some such? They might be using these to conceal their monitoring equipment.
clipped from antwrp.gsfc.nasa.gov

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.

See Explanation. Clicking on the picture will download<br /> the highest resolution version available.
The unusual hole pictured above was found on the slopes of the giant Martian volcano
Arsia Mons.
The above hole is about the size of a
football field
and is so deep that it is completely
unilluminated by the Sun.
Such holes and
underground caves
might be prime targets for
future spacecraft,
robots, and even the next generation of
human interplanetary explorers.
  blog it
Share and Enjoy:These icons link to social bookmarking sites where readers can share and discover new web pages.
  • blogmarks
  • co.mments
  • del.icio.us
  • De.lirio.us
  • digg
  • Fark
  • Furl
  • YahooMyWeb