Huge hole in Mars

 Apod Image 1207 Marshole2 Hirise 2560

This "hole in Mars," imaged by the Mars Reconnaissance Orbiter, is an opening into an underground cave. The hole is approximately 35 meters across. NASA reports, "Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life."