Moons of Mars its 30-hour orbit, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars. Both moons are tidally locked, always presenting the same face towards Mars. Since Phobos orbits Mars faster than the planet itself rotates, tidal forces are slowly but steadily decreasing its orbital radius. At some point in the future, when it approaches Mars closely enough (see Roche limit), Phobos will be broken up by these tidal forces. Several strings of craters on the Martian surface, inclined further from the equator the older they are, suggest that there may have been
History of Solar System formation and evolution hypotheses stars and clusters and the star-clouds of the Milky Way", which proposed that the planets formed in the outer Solar System and were captured by the Sun; the moons were formed in thus manner and were captured by the planets. This caused a feud with Forest Moulton, who co-developed the planetesimal hypothesis. A preview was presented in 1909 at a meeting of the ASP (Astronomical Society of the Pacific) at the Chabot Observatory in Oakland, Cal., and newspaper headlines blared "Prof. See's Paper Causes Sensation" (San Francisco Call) and "Scientists in Furore Over Nebulae" (San Francisco Examiner). Our current knowledge