NASA recently shared a photo of a hole in the surface of Mars, which researchers are saying is an "opening to an underground cavern".  A Michigan Tech professor who co-authors a NASA blog, says this may be a good place to begin the search for "Martian life".

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This "hole in Mars" is located on the slopes of Pavonis Mons, a huge volcano on the Martian equator. The photo was taken in 2011 by the Mars Reconnaissance Orbiter. The opening in the photo is about 115 feet across and 65 feet deep. It was featured in NASA's Astronomy Picture of the Day blog post for March 1st. In a description of the picture, the two authors, Robert Nemiroff, Professor of Physics at Michigan Tech and NASA staff scientist Jerry Bonnell said:

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.

Here's the post, with the photo and description.