This is old but worth reviewing:

During a recent interview on an American news channel, Apollo 11 astronaut, Buzz Aldrin, sensationally announced that there is a monolith on Phobos - one of the Moons of Mars. After a brief search, we came across these pictures that do appear to show such an object!

The 'monolith', was snapped from 165 miles away using a special high resolution camera onboard the Mars Reconnaissance Orbiter. These pictures bring into question whether there was once life on the Red Planet? Of course, this isn’t the first unusual artefact to be found on the Red Planet. The 'Face On Mars', as well as the 'D & M Pyramid' are just a few of the unusual anomalies that have been discovered in recent years

The picture above shows the monolith as it appears on the surface of Phobos, and also a zoomed in view. But scientists at the University of Arizona, who captured the original image, claim that it's just an unremarkable boulder, which could measure up to five metres across.

Yisrael Spinoza, a spokesman for the HiRISE department of the University's Lunar and Planetary Laboratory said: 'It would be unwise to refer to it as a "monolith" or "structure" because that implies something artificial, like it was put there by someone.

Buzz Aldrin talks about 'Monolith On Mars'

Speaking on a U.S. cable television channel last week, Buzz Aldrin said: 'We should visit the moons of Mars. There's a monolith there - a very unusual structure on this little potato shaped object that goes around Mars once every seven hours. An image sent by the Viking spacecraft in 1976 seemed to show a human-like face on the surface of Mars When people find out about that they are going to say, "Who put that there? Who put that there?" Well the universe put it there, or if you choose God put it there.'

In 2007 the Canadian Space Agency funded a study for an unmanned mission to Phobos known as PRIME (Phobos Reconnaissance and International Mars Exploration). The building-sized monolith is the main proposed landing site but not because scientists suspect UFO activity