An areostationary orbit or areosynchronous equatorial orbit (abbreviated AEO) is a circular areosynchronous orbit in the Martian equatorial plane about 20,428 km (12,693 mi) above the surface, any point on which revolves about Mars in the same direction and with the same period as the Martian surface. Areostationary orbit is a concept similar to Earth's geostationary orbit. The prefix areo- derives from Ares, the ancient Greek god of war and counterpart to the Roman god Mars, with whom the planet was identified. The modern Greek word for Mars is Άρης (Áris).
To date, no artificial satellites have been placed in this orbit, but it is of interest to some scientists foreseeing a future telecommunications network for the exploration of Mars. The proposed Mars One mission includes a communications system featuring amongst others things an areostationary satellite. An asteroid or station placed in areostationary orbit could also be used to construct a Martian space elevator for use in transfers between the surface of Mars and orbit.
Orbital speed (how fast a satellite is moving through space) is calculated by multiplying the angular speed of the satellite by the orbital radius:
By this formula we can find the geostationary-type orbit of an object in relation to Mars (this type of orbit above is referred to as an areostationary orbit if it is above Mars).
We know the mass of Mar is 6.39 x , and the rotational period of Mars is 24 hours and 39 minutes. If we do the math we get 20,428 km (12693 mi). 
Any satellites in areostationary orbit will likely suffer from increased orbital station keeping costs, because the Clarke belt of Mars lies between the orbits of the planet's two natural satellites. Phobos has a semi-major axis of 9,376 km, and Deimos has a semi-major axis of 23,463 km. The close proximity to Phobos in particular (the larger of the two moons) will cause unwanted orbital resonance effects that will gradually shift the orbit of areostationary satellites.
- Lay, N.; C. Cheetum; H. Mojaradi; J. Neal (15 November 2001). "Developing Low-Power Transceiver Technologies for In Situ Communication Applications" (PDF). IPN Progress Report 42-147. 42 (147): 22. Retrieved 2012-02-09.
- "Communications System". mars-one.com. Retrieved July 16, 2013.
- "Calculating the Radius of a Geostationary Orbit - Ask Will Online". Ask Will Online. 2012-12-27. Retrieved 2017-11-21.
- "Stationkeeping in Mars orbit". www.planetary.org. Retrieved 2017-11-21.
- Mars Network - Marsats - NASA site devoted to future communications infrastructure for Mars exploration
- Bandwidth available from an areostationary satellite
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