Man in the Moon then cooled, becoming smooth, basalt rock. The near side of the Moon, containing these maria that make up the man, is always facing Earth. This is due to a tidal locking or synchronous orbit. Thought to have occurred because of the gravitational forces partially caused by the Moon's oblong shape, its rotation has slowed to the point where it rotates exactly once on each trip around the Earth. This causes the near side of the Moon to always turn its face toward Earth. Man in the Moon The Man in the Moon refers to any of several pareidolic images of
Frozen orbit propellant. For most spacecraft, changes to orbits are caused by the oblateness of the Earth, gravitational attraction from the sun and moon, solar radiation pressure, and air drag. These are called "perturbing forces". They must be counteracted by maneuvers to keep the spacecraft in the desired orbit. For a geostationary spacecraft, correction maneuvers on the order of 40–50 m/s per year are required to counteract the gravitational forces from the sun and moon which move the orbital plane away from the equatorial plane of the Earth. For sun-synchronous spacecraft, intentional shifting of the orbit plane (called "precession") can be used