The Phobos monolith is a surface feature on the moon Phobos, which orbits Mars.
A monolith is a large, single piece of rock.
Monoliths also occur naturally on Earth such as the devilstower.
It has been suggested that the Phobos monolith may be a piece of impact ejecta.
Some even suggest that the monolith is an artificial structure.
Who knows ?

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