Humankind might be one step closer to uncovering alien life after an eerie crater was discovered on the surface of Mars.

NASA said the unusual feature, first snapped by the Mars Reconnaissance Orbiter in 2011, "appears to be an opening to an underground cavern".

The space agency shared the picture over the weekend, with NASA scientists Robert Nemiroff and Jerry Bonnel explaining the strange discovery.

NASA shared the photo of the hole on the surface of Mars. (Supplied)

"The hole was discovered by chance in 2011 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," the scientists explained.

"Shown in representative colour, [the hole] appears to be an opening to an underground cavern."

NASA said subsequent 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.

A NASA image of Mars. (AAP) (AAP)

"Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern," the scientists 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.

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