This illustration provides a comparison for how big the moons of Mars appear to be, as seen from the surface of Mars, in relation to the size that Earth's moon appears to be when seen from the surface of Earth. Earth's moon actually has a diameter more than 100 times greater than the larger martian moon, Phobos. However, the martian moons orbit much closer to their planet than the distance between Earth and Earth's moon. // NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M Univ.