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. The unusual hole pictured above was found on the slopes of the giant Martian volcano Arsia Mons.

    This picture looks like it was Photoshopped, but it wasn’t.
    Click on photo for full size.

    From NASA.