Reiner Gamma (γ) is a geographical feature of the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

known as a lunar swirl. It is one of the most visible lunar swirls from Earth, visible from most telescopes. It was originally thought to be a lunar

highland Highlands or uplands are areas of high elevation such as a mountainous region, elevated mountainous plateau or high hills. Generally speaking, upland (or uplands) refers to ranges of hills, typically from up to while highland (or highlands) is ...

, but scientists eventually realized that it cast no shadow on the moon.

Origin

The origin of Reiner Gammalike other lunar swirlsis not completely understood. It is associated with a localized

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

, but not with any particular irregularities in the surface. Similar features have been discovered in

Mare Ingenii Mare Ingenii (Latin ''ingeniī'', the "Sea of Cleverness") is one of the few lunar mare features on the far side of the Moon. The mare sits in the Ingenii basin, which is of the Pre-Nectarian epoch, which lies in turn in the outer part of the old ...

and

Mare Marginis Mare Marginis (Latin ''marginis'', the "Sea of the Edge") is a lunar mare that lies on the very edge of the lunar nearside. The selenographic coordinates of this feature are 13.3° N, 86.1° E, and the diameter is 358 km. The name is Latin ...

by orbiting spacecraft. The feature on Mare Ingenii is located at the lunar opposite point from the center of

Mare Imbrium Mare Imbrium (Latin ''imbrium'', the "Sea of Showers" or "Sea of Rains", "Sea of Tears") is a vast lava plain within the Imbrium Basin on the Moon and is one of the larger craters in the Solar System. The Imbrium Basin formed from the colli ...

. Likewise the feature on Mare Marginis is opposite the midpoint of

Mare Orientale Mare Orientale (Latin ''orientāle'', the "eastern sea") is a lunar mare. It is located on the western border of the near side and far side of the Moon, and is difficult to see from an Earthbound perspective. Images from spacecraft have reveale ...

. Thus one hypothesis is that the feature resulted from seismic energies generated by the impacts that created these maria. However, no such lunar mare formation is on the opposite side of the Moon from Reiner Gamma.

Location and Features

Reiner Gamma is located on the

Oceanus Procellarum Oceanus Procellarum ( la, Ōceanus procellārum, lit=Ocean of Storms) is a vast lunar mare on the western edge of the near side of the Moon. It is the only one of the lunar maria to be called an "Oceanus" (ocean), due to its size: Oceanus Proc ...

, west of the crater Reiner. Its center is located at selenographic coordinates . It has an overall length of about 70 kilometres. The feature has a higher albedo than the relatively dark

mare A mare is an adult female horse or other equine. In most cases, a mare is a female horse over the age of three, and a filly is a female horse three and younger. In Thoroughbred horse racing, a mare is defined as a female horse more than four ...

surface, with a diffuse appearance and a distinctive swirling, concentric oval shape. Related albedo features continue across the surface to the east and southwest, forming loop-like patterns over the mare. The central feature of Reiner Gamma resembles the dipolar formation created by iron filings on a surface with a

bar magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nicke ...

on the underside. Low-orbiting

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, p ...

have observed a relatively strong magnetic field associated with each of these albedo markings. Some have speculated that this magnetic field and the patterns were created by

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

ary impacts. However the true cause remains uncertain. Reiner Gamma's magnetic field strength is approximately , measured from an altitude of . This is one of the strongest localized

magnetic anomalies In geophysics, a magnetic anomaly is a local variation in the Earth's magnetic field resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying ...

on the Moon. The surface field strength of this feature is sufficient to form a mini-magnetosphere that spans at the surface, forming a thick region of enhanced plasma where the

solar wind The solar wind is a stream of charged particles released from the upper atmosphere of the Sun, called the corona. This plasma mostly consists of electrons, protons and alpha particles with kinetic energy between . The composition of the sola ...

flows around the field. As the particles in the solar wind are known to darken the lunar surface, the magnetic field at this site may account for the survival of this albedo feature. In early

lunar Lunar most commonly means "of or relating to the Moon". Lunar may also refer to: Arts and entertainment * ''Lunar'' (series), a series of video games * "Lunar" (song), by David Guetta * "Lunar", a song by Priestess from the 2009 album ''Prior t ...

map A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes. Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...

s by

Francesco Maria Grimaldi Francesco Maria Grimaldi, SJ (2 April 1618 – 28 December 1663) was an Italian Jesuit priest, mathematician and physicist who taught at the Jesuit college in Bologna. He was born in Bologna to Paride Grimaldi and Anna Cattani. Work Between 1 ...

, this feature was incorrectly identified as a

crater Crater may refer to: Landforms *Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet *Explosion crater, a hole formed in the ground produced by an explosion near or below the surfac ...

. His colleague

Giovanni Riccioli Giovanni Battista Riccioli, Society of Jesus, SJ (17 April 1598 – 25 June 1671) was an Italian astronomer and a Catholic church, Catholic priest in the Jesuit order. He is known, among other things, for his experiments with pendulums and with f ...

then named it ''Galilaeus'', after

Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...

. The name was later transferred northwest to the current crater Galilaei.

References

Other references

* Ewen A. Whitaker, ''Mapping and Naming the Moon: A History of Lunar Cartography and Nomenclature'', Cambridge University Press,

1999 File:1999 Events Collage.png, From left, clockwise: The funeral procession of King Hussein of Jordan in Amman; the 1999 İzmit earthquake kills over 17,000 people in Turkey; the Columbine High School massacre, one of the first major school shootin ...

, .

External links

* {{cite web , last = Phillips , first = Tony , date = 2006-06-26 , url = https://science.nasa.gov/headlines/y2006/26jun_lunarswirls.htm , archive-url = https://web.archive.org/web/20060630004818/http://science.nasa.gov/headlines/y2006/26jun_lunarswirls.htm , url-status = dead , archive-date = 2006-06-30 , title = Mysterious Lunar Swirls , publisher = Science@NASA , access-date = 2006-06-27 * Overexposed 35mm Nikon camera image of Reiner Gamma from

Apollo 17 Apollo 17 (December 7–19, 1972) was the final mission of NASA's Apollo program, the most recent time humans have set foot on the Moon or traveled beyond low Earth orbit. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on ...

AS17-158-23895
*

Lunar Orbiter 4 Lunar Orbiter 4 was a robotic U.S. spacecraft, part of the Lunar Orbiter program, Lunar Orbiter Program, designed to orbit the Moon, after the three previous orbiters had completed the required needs for Project Apollo, Apollo mapping and site s ...

image showing Reiner Gamma in upper left
IV-157-H1
Geological features on the Moon