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
Mars One from any money earned from guest appearances (which would amount to a minimal portion of the estimated $6 billion required for the mission). Finally, despite being one of 100 finalists, Roche himself has never spoken to any Mars One employee or representative in person, and instead of psychological or psychometric testing as is normal for astronaut candidates (especially for a lengthy, one-way mission), his interview process consisted of a 10-minute Skype conversation. In April 2015, Mars One's CEO Bas Lansdorp admitted that their 12-year plan for landing humans on Mars by 2027 is mostly fiction. Robert Zubrin, advocate for crewed