A mass concentration or mascon is a region of a planet or moon's crust that contains a large amount of material that is denser than average for that body. The result is a minute but measurable increase in the local gravity. Gravity is the force of attraction between massive particles due to their mass. ...

Mascons can have a variety of causes. On Earth, they frequently indicate processess occurring in the upper mantle such as plumes of magma. On the Moon, most mascons are thought to be remnants of asteroids that impacted the surface, or the effects of magmatic upwelling from the lunar interior after such impacts. The Moon's mascons alter the local gravity in certain regions sufficiently so that low, uncorrected satellite orbits around the Moon, are unstable on a timescale of months or years, distorting the successive orbits until the satellite impacts the surface. Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... Earth cutaway from core to exosphere. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ...

The lunar mascons were discovered by Paul Muller and William Sjogren of the NASA Jet Propulsion Laboratory (JPL) in 1968 (Science, 161, 1968) from analysis of the highly precise navigation data from the unmanned pre-Apollo Lunar Orbiter spacecraft. At that time one of NASA's highest priority "tiger team" projects was to explain why the Lunar Orbiter spacecraft being used to test the accuracy of Project Apollo navigation were experiencing errors in predicted position of ten times the mission specification (2km instead of 200m). This meant that the predicted landing areas were 100 times as large as those being carefully defined for reasons of safety. The aforementioned problem with lunar orbital effects was revealed as the cause by this discovery. William Wollenhaupt and Emil Schiesser of the NASA Manned Spacecraft Center in Houston then worked out the "fix" that was first applied to Apollo 12 and permitted its landing within 30m of the target, the previously landed Surveyor 3 spacecraft. The Caltech Jet Propulsion Laboratory (JPL) near Pasadena, California builds and operates unmanned spacecraft for NASA. JPL-run projects include the Galileo Jupiter mission and the Mars rovers, including the 1997 Mars Pathfinder and the twin 2003 Mars Exploration Rovers. ... Lunar orbiter spacecraft (NASA) The Lunar Orbiter program was a series of five unmanned Lunar orbiter missions launched by the United States in 1966 through 1967 with the purpose of mapping the lunar surface before the Apollo landings. ... Apollo Program insignia Project Apollo was a series of human spaceflight missions undertaken by the United States of America using the Apollo spacecraft and Saturn lauch vehicle, conducted during the years 1961-1972. ... An aerial view of the complete Johnson Space Center facility in Houston, Texas in 1989. ... Apollo 12 was the sixth manned mission in the Apollo program and the second to land on the Moon. ... Surveyor 3 was the third lunar lander of the Surveyor program that explored the Moon. ...