Phobos, though larger than Deimos, crosses the Martian night sky in four hours, he said.

CNN: Mars' geology 'more like Earth than the moon'

The first observations were made of Deimos, the smaller of Mars' two moons.

CNN: Mars' geology 'more like Earth than the moon'

In 1877, U.S. astronomer Asaph Hall discovered Deimos, ("Panic" in Greek) a satellite of Mars, at the Naval Observatory in Washington.

CNN: Tuesday,

Thirteen images were beamed back to Earth, and Dr. Nicholas Thomas of the Max Planck Institute in Germany said Deimos would never be more than a "spot" passing over Mars.

CNN: Mars' geology 'more like Earth than the moon'