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 in 2024, and one in 2026 which would not be returning to Earth. Although the announcement garnered much international publicity, the concept has been criticized by scientists, engineers, and those in the aerospace industry. Mars One is noted as being very short on funding, lacking critical concepts about hardware, life support, electrical power supply, and has been criticized as glossing over logistics, medical concerns, and protection against space radiation. The concept has been called a suicide mission both in academia, spaceflight, and international news. By February 2015, two conceptual studies were done by contractors. Despite the criticism and lack of