You have to admit this is interesting. This hole on Mars is slightly more than 100 meters across. It is so deep that there is no reflected sunlight. The sides of the hole aren't cracked or raised, there is no ejecta, which rules out a meteor impact. It's on the flanks of a volcano so perhaps a lava tube, but there is no hint of lava or anything downstream from it. Also, the surrounding terrain seems to be prettymuch totally unaffected, it's like someone took a giant laser and just punched a whole through the surface.