Apollo (crater)
Encyclopedia
Apollo is an enormous impact crater
Impact crater
In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 located in the southern hemisphere
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

 on the far side of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

. This formation dwarfs the large crater Oppenheimer
Oppenheimer (crater)
Oppenheimer is a large lunar crater that lies on the Far side of the Moon. It lies along the western outer ampart of the immense walled plain Apollo. Nearby features of note include the dark-floored crater Maksutov to the southwest, and Davisson to the west-southwest...

 that is located next to the western rim. The crater Barringer
Barringer (lunar crater)
Barringer is a lunar impact crater that is located on the southern hemisphere on the far side of the Moon. It is attached to the north-northeastern rim of the walled basin named Apollo, and lies to the southeast of Plummer...

 lies across the northern wall. To the southeast is the crater Anders
Anders (crater)
Anders is a worn lunar impact crater that is located in the southern hemisphere on the far side of the Moon. It lies just to the southeast of the outer rim of the huge walled basin named Apollo. To the south-southeast is the crater Leavitt....

, and Kleymenov
Kleymenov (crater)
Kleymenov is a crater on the far side of the Moon. It is located near the east-northeastern outer wall of the huge walled plain Apollo, and to the west-northwest of the large crater Chebyshev. To the north is Mariotte....

 is just to the east of the rim.

Apollo is a double-ringed walled plain whose inner ring is roughly half the diameter of the outer wall. Both the outer wall and the interior have been heavily worn and eroded by subsequent impacts, so that significant parts of the outer and inner walls now consist of irregular and incised sections of mountainous arcs.

The interior floor is covered in a multitude of craters of various sizes. Several of the more notable craters have received names. The IAU
International Astronomical Union
The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

 used the eponym
Eponym
An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...

s of people associated with the Apollo program when designating some of these formations.

Sections of Apollo's interior have been resurfaced with lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

, leaving patches of the floor with a lower albedo
Albedo
Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

 than the surroundings. There is a large patch of this lunar mare
Lunar mare
The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

 in the middle part of the inner ring, which contains some ray system
Ray system
A ray system comprises radial streaks of fine ejecta thrown out during the formation of an impact crater, looking a bit like many thin spokes coming from the hub of a wheel. The rays can extend for lengths up to several times the diameter of their originating crater, and are often accompanied by...

 markings. A long stretch of the mare lies along the southern part of the crater. There is also a smaller section near the western rim.

Interior craters

Several craters within the Apollo impact have been named to honor deceased NASA employees.

Dryden
Dryden (crater)
Dryden is a lunar impact crater that is located on the southern hemisphere on the far side of the Moon. It lies within the huge walled plain called Apollo, and is one of several features within that basin named after people associated with the Apollo program. Apollo itself has an inner ring, and...

 is attached to the west-northwestern exterior of the inner ring. Chaffee
Chaffee (crater)
Chaffee is a lunar impact crater that is located in the southern hemisphere on the far side of the Moon. It lies within the huge walled plain Apollo, and is one of several craters in that formation named for astronauts and people associated with the Apollo program. This basin is a double-ringed...

 is a similar-sized crater that lies partly across the southwest section of the inner ring. In the southeast part of the outer crater is Borman
Borman (crater)
Borman is a lunar impact crater that is located in the southern hemisphere on the far side of the Moon. It lies across the southeast section of the mountainous inner ring, within the walled basin named Apollo....

. Inside the inner ring are the craters Resnik
Resnik (crater)
Resnik is a small lunar crater that is located within the interior of the huge walled plain Apollo, on the Moon's far side. Apollo is a double-ringed formation with a central floor that has been flooded with basaltic lava. Resnik is located at the northern edge of the dark area of the surface...

, McAuliffe
McAuliffe (crater)
McAuliffe is a small lunar impact crater that is located on the Moon's far side. It lies within the inner ring of the double-ringed walled plain Apollo, about one crater diameter to the northeast of the crater Resnik. To the southeast of McAuliffe lies the crater pair of Jarvis and McNair.McAuliffe...

, and Onizuka
Onizuka (crater)
Onizuka is a small lunar impact crater that lies within the inner ring of the walled plain Apollo. The central portion of Apollo has been covered by dark basaltic lava, and Onizuka lies at the southern edge of this plain. To the southeast of Onizuka is the crater Borman, and to the west-southwest...

, and the Jarvis
Jarvis (crater)
Jarvis is a crater that lies on the far side of the Moon. It is located within the walled plain Apollo, and lies in the eastern half of this basin within the interior ring....

McNair
McNair (crater)
McNair is a small lunar impact crater on the far side of the Moon. It lies within the double-ringed Apollo basin, inside the eastern part of the interior ring. Named after Ronald McNair, one of the seven astronauts who perished in the explosion of the Space Shuttle Challenger, it has partly merged...

 crater pair. The crater Smith
Smith (lunar crater)
Smith is a lunar impact crater that is located within the huge walled plain Apollo, on the far side of the Moon. This crater is attached to the west-southwestern outer rim of Scobee and it overlies the northern edge of the inner mountain ring within Apollo...

 lies across the northern part of the inner ring.

In 2006 the IAU approved a proposal to name seven interior craters to honor the astronauts of the Space Shuttle Columbia
Space Shuttle Columbia disaster
The Space Shuttle Columbia disaster occurred on February 1, 2003, when shortly before it was scheduled to conclude its 28th mission, STS-107, the Space Shuttle Columbia disintegrated over Texas and Louisiana during re-entry into the Earth's atmosphere, resulting in the death of all seven crew members...

.
Crater Coordinates Diameter Name source
Chawla 42.8°S 147.5°W 15 km Kalpana Chawla
Kalpana Chawla
Kalpana Chawla was an Indian-American astronaut with NASA. She was one of seven crew members killed in the Space Shuttle Columbia disaster.-Early life:...

D. Brown 42.0°S 147.2°W 15 km David McD. Brown
David McDowell Brown
David McDowell Brown was a United States Naval Captain and a NASA astronaut. He died on his first space flight, when the Space Shuttle Columbia disintegrated during orbital reentry into the Earth's atmosphere...

Husband 40.8°S 147.9°W 29 km Richard D. Husband
Richard Douglas Husband
Rick Douglas Husband was a United States Air Force Colonel, an astronaut, and the space shuttle commander of STS-107 who was killed when the craft disintegrated after reentry into the Earth's atmosphere. Husband is a recipient of the Congressional Space Medal of Honor.-Background:Husband was born...

L. Clark 43.7°S 147.7°W 16 km Laurel B. S. Clark
McCool 41.7°S 146.3°W 21 km William C. McCool
M. Anderson 41.6°S 149.0°W 17 km Michael P. Anderson
Michael Phillip Anderson
Michael Philip Anderson was a United States Lieutenant Colonel and NASA astronaut, who was killed in the Space Shuttle Columbia disaster when the craft disintegrated after reentry into the Earth's atmosphere....

Ramon 41.6°S 148.1°W 17 km Ilan Ramon
Ilan Ramon
Ilan Ramon was a fighter pilot in the Israeli Air Force, and later the first Israeli astronaut....



Three of the crater names include the respective astronaut's first initials to distinguish them from the existing craters called Anderson
Anderson (crater)
Anderson is a lunar impact crater that is located on the far side of the Moon. It is located to the northwest of the crater Sharonov, and the satellite crater Sharanov X is attached to the southeast rim of Anderson. To the northeast is the peculiar formation Buys-Ballot, and to the east-southeast...

, Brown
Brown (crater)
Brown is a lunar impact crater that is located in the southeast part of the Moon, to the southwest of the prominent ray crater Tycho. Northwest of Brown is the crater Wilhelm, and to the west is Montanari....

 and Clark.

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