Nasa is being sued for not investigating alien life on Mars after a mystery rock turned up on the red planet.

The Martian rover Opportunity sent back images of a new rock earlier this month and scientists were unable to explain how it got there.

Steve Squyres, Nasa Mars Exploration Rover lead scientist. "It was a total surprise, we were like 'wait a second, that wasn't there before, it can't be right'. We were absolutely startled."

However, after analysis, the space agency determined it was just a rock. They said it probably arrived there through a nearby impact or that the rover knocked over the rock and scientists only noticed it later.

However, Rhawn Joseph, who describes himself as a scientist, believes Nasa should be probing the rock for alien life, to such an extent that he is suing the organisation.

Joseph has written books on alien life, the 9/11 terrorist attacks and is involved with the Journal of Cosmology. He believes that the rock may contain biological organisms, and that Nasa has a responsibility to investigate this.

He says he has asked Nasa to investigate the possibility but to no avail, so is taking legal action to compel them to do so.

In a 10 page petition to the United States District Court Northern District of California, he lays out his reasons for Nasa to investigate the rock.

Obtained by Popular Science, the petition says: "Petitioner has specifically requested and has demanded in writing the following of Nasa, Nasa's chief administrator Bolden, and Nasa's rover team: A) take 100 high resolution close-up infocus photos of the specimen identified in Sol 3540, at various angles, from all sides, and from above down into the "bowl" of the specimen, and under appropriate lighting conditions which minimise glare.

"B) Take a minimum of 24 microscopic in-focus images of the exterior, lip, walls, and interior of the specimen under appropriate lighting conditions. C) NASA, and the rover team must make public and supply Petitioner with all high resolution photos and images of that specimen as demanded in A and B."

See the document below: