Pictures of an unexpected hole on the surface of Mars have prompted new speculation about life on the red planet.

The hole, pictured left, was discovered by chance on images of the dusty slopes of Mars’ Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars

According to NASA, the hole appears to be an opening to an underground cavern.

Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep.

NASA states that scientists are still speculating as to why there is a circular crater surrounding the hole, as well as what the full extent of the underlying cavern is.

“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.,” the space agency states.

“These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.”

The image is published courtesy of: NASA, JPL, U. Arizona