Moons of Mars binary asteroid that separated under 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' volume) is inconsistent with an asteroidal origin. Observations of Phobos in the thermal
Mars One but that accommodating Mars One requirements would require some additional work and that such action was not a part of the current focus of SpaceX. SpaceX has no ongoing contracts with Mars One. The first Mars One cargo mission to Mars is proposed to launch by 2022, followed by a crewed mission in 2024, but without funds, hardware, and without a launcher it is seen as unlikely to happen. A hypothetical crewed interplanetary spacecraft, for which there are no concept design studies, would be assembled in low Earth orbit and comprise two propellant modules: a Transit Living Module (discarded just