Reiner Gamma (γ) is a geographical feature of the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

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, ''upland'' refers to a range of hills, typically from up to , while ''highland'' is usually reserved for range ...

, but scientists eventually realized that it cast no shadow on the moon. Aldo Ferruggia - Hevelius-Reiner

Origin

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

magnetic field A magnetic field (sometimes called B-field) is a physical 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 ...

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

Mare Marginis Mare Marginis (Latin for '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. This mare differs from most ...

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") is a vast lunar mare, 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 collision ...

. 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 revea ...

. 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 ( ; from ) 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 Procellarum is the largest of the maria ("s ...

, 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 equidae, 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 th ...

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, nickel, c ...

on the underside. Low-orbiting

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

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 warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

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 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 Sun's outermost atmospheric layer, the Stellar corona, corona. This Plasma (physics), plasma mostly consists of electrons, protons and alpha particles with kinetic energy betwee ...

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

map A map is a symbolic depiction of interrelationships, commonly spatial, between things within a space. A map may be annotated with text and graphics. Like any graphic, a map may be fixed to paper or other durable media, or may be displayed on ...

s by

Francesco Maria Grimaldi Francesco Maria Grimaldi (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 164 ...

, this feature was incorrectly identified as a

crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

. His colleague Giovanni Riccioli then named it ''Galilaeus'', after

Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...

. 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 1999 was designated as the International Year of Older Persons. Events January * January 1 – The euro currency is established and the European Central Bank assumes its full powers. * January 3 – The Mars Polar Lander is launc ...

, .

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 eleventh and final mission of NASA's Apollo program, the sixth and most recent time humans have set foot on the Moon. Commander Gene Cernan and Lunar Module Pilot Harrison Schmitt walked on the Moon, ...

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
Surface features of the Moon