Moons of Mars Sun's angular diameter as seen from Mars, by contrast, is about 21'. Thus there are no total solar eclipses on Mars, as the moons are far too small to completely cover the Sun. On the other hand, total lunar eclipses of Phobos are very common, happening almost every night. The motions of Phobos and Deimos would appear very different from that of our own Moon. Speedy Phobos rises in the west, sets in the east, and rises again in just eleven hours, while Deimos, being only just outside synchronous orbit, rises as expected in the east but very slowly. Despite
Exploration of Mars a focus on Phobos. Phobos 1 lost contact on the way to Mars. Phobos 2, while successfully photographing Mars and Phobos, failed before it was set to release two landers to the surface of Phobos. Roughly two-thirds of all spacecraft destined for Mars have failed without completing their missions, and it has a reputation as a difficult space exploration target. Missions that ended prematurely after Phobos 1 and 2 (1988) include (see Probing difficulties section for more details): Following the 1993 failure of the Mars Observer orbiter, the NASA Mars Global Surveyor achieved Mars orbit in 1997. This mission was