Phobos (moon) tidal forces. Phobos could be a second-generation Solar System object that coalesced in orbit after Mars formed, rather than forming concurrently out of the same birth cloud as Mars. Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a large planetesimal. The high porosity of the interior of Phobos (based on the density of 1.88 g/cm, voids are estimated to comprise 25 to 35 percent of Phobos's volume) is inconsistent with an asteroidal origin. Observations of Phobos in the thermal infrared suggest a composition containing
Phobos (audio drama) Phobos (audio drama) Phobos is an audio drama based on the long-running British science fiction television series "Doctor Who". This audio drama was produced by Big Finish Productions and was broadcast on BBC 7 on 28 January 2007. The Doctor and Lucie land on Phobos, the moon of Mars, which has become popular with extreme sports fans in the future, due to a wormhole on the surface which is used for bungee jumping. The Doctor and Lucie listen to Kai Tobias's stories of monsters on the surface, although no-one takes him seriously. Later the monsters from Tobias's stories appear and