Apparent retrograde motion notable on Mars which has two natural satellites, Phobos and Deimos. Both moons orbit Mars in an eastward (prograde) direction, however Deimos has an orbital period of 1.23 Martian sidereal days, making it supersynchronous, whereas Phobos has an orbital period of 0.31 Martian sidereal days making it subsynchronous. Consequently, although both moons are travelling in an eastward (prograde) direction, they appear to be travelling in opposite directions when viewed from the surface of Mars due to their orbital periods in relation to the rotational period of the planet. All other planetary bodies in the Solar System also appear to periodically
Mars One all the research, supplier Lockheed Martin says that the technologies were viable. Another serious concern uncovered in the research conducted by MIT is replacement parts. The PhD candidates estimated the need for spare parts in a Mars colony based on the failure rates of parts on the ISS. They determined that a resupply mission every two years would be necessary unless a large space in the initial launch were to be reserved for extra materials. Lansdorp commented on this saying, "They are correct. The major challenge of Mars One is keeping everything up and running. We don't believe what we