Mascon (from the English. Mass concentration - "mass concentration") - the region of the lithosphere of the planet or natural satellite, causing positive gravitational anomalies . The most famous are the lunar mascones, which were discovered and localized by disturbances in the movements of the artificial satellites of the moon . Most often, mascones are located under the moon seas , having a rounded shape.
The Masons were discovered by Paul Muller and William Szogren  , employees of the NASA Jet Propulsion Laboratory, in 1968, as a result of a rigorous analysis of the orbit parameters of the Lunar orbiter automatic stations. Due to the special importance of the man’s landing program on the moon, a special team was created at NASA to explain the deviations in the trajectory of the Lunar Orbiter spacecraft, which was used to experimentally verify the calculations of the navigation of the Apollo manned spacecraft . Orbital deviations exceeded the calculated ones by a factor of 10 (2 km instead of 200 m), which gave a 100-fold error at the landing site and threatened the safety of the crew. Gravitational disturbances in the gravitational field of the moon well explained this behavior of an artificial satellite. William Wallenhaupt and Emil Schisser from the NASA control center in Houston calculated the amendment that allowed Apollo 12 to land 160 meters from its target, which had landed two years earlier on the Surveyor 3 spacecraft .
Later, according to the data of the Lunar Prospector apparatus, obtained in 1998-1999, a detailed map of the lunar mascones was compiled. Masons are located mainly under large rounded seas: Rains , Clouds , Clarity , Crises , Nectar , Humidity , under the East , as well as in the area between the Gulf of Zno and the Central Gulf .
The existence of masons on Mars and Mercury is very likely  .
There were three versions of the origin of the masons:
- Muller and Sjögren suggested that mascones consist of dense substances, for example, nickel and iron, and are the remnants of cosmic bodies that fell on the moon and “buried” in the lunar “seas”. However, this hypothesis is too artificial, since it is difficult to assume that in nature there were bodies the size of an asteroid made of iron and nickel.
- The second hypothesis was proposed by the American scientist J. Gilvarry. In his opinion, mascones are associated with strata of sedimentary rocks formed on the site of the ancient lunar seas (in the literal sense of the word). Gilvarry, long before the discovery of the masons, expressed the idea that in the first billion years of the moon's existence, it had a hydrosphere . After water evaporation, deposits of sedimentary rocks were formed on the site of the seas, the average density of which is 2.4 g / cm³. Despite the fact that their density is low, they create an excess of mass, since even before their occurrence the basins of the seas (formed, according to Gilvarry, due to the fall of large bodies on the Moon) underwent isostatic alignment with the continents surrounding them.
- According to the most widespread theory proposed by R. Baldwin, the origin of masons is associated with the impacts of large cosmic bodies, as a result of which giant, many-kilometer-deep excavations were created in the lunar crust. Next, geological processes came into effect. Lower, more dense than the crust, the molten mantle squeezed up the bottom of the geological depression formed by the impact - a notch, forming a lens under it, consisting of the substance of the raised mantle. Some of the mantle material erupted in the form of lava to the surface and filled the rest of this depression. Thus, in some places of the lunar crust, regions were formed where its density turned out to be higher than in other areas.
- GRAIL - a program for studying the gravitational field and the internal structure of the moon.
- Paul Muller and William Sjogren. Mascons: lunar mass concentration (Eng.) // Science. - 1968. - Vol. 161 . - P. 680-684 .
- Glossary of Cosmic Terms, Mascones . Federal Space Agency.
- Mark Wieczorek and Roger Phillips. Lunar multiring basins and the cratering process (English) // Icarus . - Elsevier , 1999 .-- Vol. 139 . - P. 246—259 .
- A. Konopliv, S. Asmar, E. Carranza, W. Sjogren, and D. Yuan. Recent gravity models as a result of the Lunar Prospector mission (English) // Icarus : journal. - Elsevier , 2001 .-- Vol. 50 . - P. 1-18 .