Fra Mauro formation
Encyclopedia
The Fra Mauro formation (or Fra Mauro Highlands) is a lunar
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...

 geological formation on the near side of the Moon
Near side of the Moon
The near side of the Moon is the lunar hemisphere that is permanently turned towards the Earth, whereas the opposite side is the far side of the Moon. Only one side of the Moon is visible from Earth because the Moon rotates about its spin axis at the same rate that the Moon orbits the Earth, a...

 that served as the landing site for the American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 Apollo 14
Apollo 14
Apollo 14 was the eighth manned mission in the American Apollo program, and the third to land on the Moon. It was the last of the "H missions", targeted landings with two-day stays on the Moon with two lunar EVAs, or moonwalks....

 mission in 1971. It is named after the 80-kilometer-diameter crater Fra Mauro
Fra Mauro (crater)
Fra Mauro is the worn remnant of a walled lunar plain. It is part of the surrounding Fra Mauro formation, being located to the northeast of Mare Cognitum and southeast of Mare Insularum...

, located within it. The formation, as well as Fra Mauro crater, take their names from a 15th century Italian monk and mapmaker
Fra Mauro
Fra Mauro, O.S.B. Cam., was a 15th-century Camaldolese monk who lived in the Republic of Venice. He was a monk of the Monastery of St. Michael, located on the island of Murano in the Venetian Lagoon. It was there that he maintained a cartography workshop.In his youth, Mauro had traveled...

 of the same name. Apollo 13
Apollo 13
Apollo 13 was the seventh manned mission in the American Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, at 13:13 CST. The landing was aborted after an oxygen tank exploded two days later, crippling the service module upon which the Command...

 was originally scheduled to land in the Fra Mauro highlands, but was unable to due to an in-flight technical failure.

Fra Mauro is thought to have been formed from ejecta
Ejecta
Ejecta can mean:*In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor...

, or debris, from the impact which formed Mare Imbrium
Mare Imbrium
Mare Imbrium, Latin for "Sea of Showers" or "Sea of Rains", is a vast lunar mare filling a basin on Earth's Moon and one of the larger craters in the Solar System. Mare Imbrium was created when lava flooded the giant crater formed when a very large object hit the Moon long ago...

. During Apollo 14, the crew members sampled ejecta from Cone crater, a crater in close proximity to the immediate landing site of that mission, which provided insight into the composition of material deep inside the formation. Data from the mission has helped to determine the approximate age of Mare Imbrium, suggesting that it is no more than about 4.25 billion years old.

Formation and geography

Fra Mauro is a widespread hilly geological area covering large portions of the lunar surface around Mare Imbrium, and is thought to be composed of ejecta from the impact which formed Imbrium. The area is primarily composed of relatively low ridges and hills, between which exist undulating valleys. Much of the ejecta blanket
Ejecta blanket
An ejecta blanket is a generally symmetrical apron of ejecta that surrounds crater; it is layered thickly at the crater’s rim and thin to discontinuous at the blanket’s outer edge....

 from the Imbrium impact is covered with debris from younger impacts and material churned up by possible moonquakes. Debris found in the formation may have originated from deep beneath the original crust, and samples collected there could give insight into the geologic history of the Moon. The petrology
Petrology
Petrology is the branch of geology that studies rocks, and the conditions in which rocks form....

 of the formation, based on data obtained on Apollo 14, indicates a history of impact and ejection possibly spanning over approximately 500 million years.

A relatively recent impact created Cone crater, 1,000 feet across and 250 feet deep, near the landing site of Apollo 14. One of the main objectives of that mission was to sample the original Imbrium material located on its rim.

Samples obtained of the Fra Mauro formation during Apollo 14 suggest that the impact that formed the Imbrium basin is no older than 4.25 billion years.

Geology

Analysis of Apollo 14 samples suggests that there are five major geologic constituents present in the immediate landing area: regolith
Regolith
Regolith is a layer of loose, heterogeneous material covering solid rock. It includes dust, soil, broken rock, and other related materials and is present on Earth, the Moon, some asteroids, and other terrestrial planets and moons.-Etymology:...

 breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....

s, fragmental
Rock fragment
A rock fragment, in sedimentary geology, is a sand-sized particle or sand grain that is made up of multiple grains that are connected on the grain scale. These can include grains which are sand-sized themselves , or finer-grained materials...

 breccias, igneous
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...

 lithologies
Lithology
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples or with low magnification microscopy, such as colour, texture, grain size, or composition. It may be either a detailed description of these characteristics or be a summary of...

, granulitic
Granular material
A granular material is a conglomeration of discrete solid, macroscopic particles characterized by a loss of energy whenever the particles interact . The constituents that compose granular material must be large enough such that they are not subject to thermal motion fluctuations...

 lithologies, and impact
Impact event
An impact event is the collision of a large meteorite, asteroid, comet, or other celestial object with the Earth or another planet. Throughout recorded history, hundreds of minor impact events have been reported, with some occurrences causing deaths, injuries, property damage or other significant...

-melt
Melting
Melting, or fusion, is a physical process that results in the phase change of a substance from a solid to a liquid. The internal energy of a substance is increased, typically by the application of heat or pressure, resulting in a rise of its temperature to the melting point, at which the rigid...

 lithologies. Samples of each of these compositions were recovered in one or both of two major surface units of the Apollo 14 landing site within Fra Mauro: the immediate impact blanket of Cone crater, about 25 million years old, and surrounding older terrain.
During Apollo 14, astronauts Alan Shepard
Alan Shepard
Alan Bartlett Shepard, Jr. was an American naval aviator, test pilot, flag officer, and NASA astronaut who in 1961 became the second person, and the first American, in space. This Mercury flight was designed to enter space, but not to achieve orbit...

 and Edgar Mitchell recovered ejecta material from the Cone crater impact, which is believed to have excavated Imbrium impact material from a possible depth of about 80 m (262.5 ft). Most of the samples returned from the Moon from Fra Mauro are classified as breccias from the vicinity of Cone crater.

Studies conducted upon samples from Apollo 14 have shown that the samples do not support the possibility that the landing site is floored by volcanic rocks, or basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

s. Basalts are sparse in samples of Cone crater ejecta, but somewhat abundant in samples recovered farther west, on the opposite side of the immediate landing site. Two explanations have been presented for this: (1) the majority of basalt in the landing site lies below the depth of excavation of Cone crater or (2) the presence of a basalt flow beneath the landing area excavated by a nearby crater with a diameter of 100 m (328.1 ft). It is believed that the former seems more likely, as the basalts are similar to the basalts recovered at Cone crater. It is inconclusive whether or not the recovered basalts have a direct affiliation with the landing site, as it is located in a valley between ridges, and there exists the possibility that the basalts were merely deposited there as a result of other impact events.

The Apollo 14 crew members sampled boulders in the ejecta of Cone crater. These boulders appeared to be layered
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

 and fractured breccias, contrasting from the appearance of the surrounding area because of their older age. As these boulders increase in size and number closer to Cone crater, it is believed that they originate from the greatest depth of excavation of Cone crater. These boulders show what is believed to be general characteristics of the Fra Mauro formation: clastic texture, stratification
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

, and jointing or fracturing.

Landing site selection

As Apollo 14 was an early Apollo mission, landing sites were restricted to equatorial regions for technical reasons. After Apollo 12
Apollo 12
Apollo 12 was the sixth manned flight in the American Apollo program and the second to land on the Moon . It was launched on November 14, 1969 from the Kennedy Space Center, Florida, four months after Apollo 11. Mission commander Charles "Pete" Conrad and Lunar Module Pilot Alan L...

 demonstrated the ability to land at a pre-specified landing zone, mission planners considered landings in rough, but geologically interesting areas of the Moon.

The aborted Apollo 13 mission was originally scheduled to land at Fra Mauro, with Apollo 14 scheduled to land in the Littrow
Littrow (crater)
Littrow is a lunar crater that is located in the northeastern part of the Moon's near side, on the east edge of Mare Serenitatis. Some distance to the northeast is the prominent crater Römer, while to the south is Vitruvius....

 region of Mare Serenitatis
Mare Serenitatis
Mare Serenitatis is a lunar mare that sits just to the east of Mare Imbrium on the Moon.It is located within the Serenitatis basin, which is of the Nectarian epoch. The material surrounding the mare is of the Lower Imbrian epoch, while the mare material is of the Upper Imbrian epoch...

. After Apollo 13 failed to land, it was decided to re-target Apollo 14 to Fra Mauro, as it was regarded as more interesting scientifically than the Littrow site. There, Apollo 14 had the objective of sampling ejecta from the Imbrium impact to gain insight into the Moon's geologic history
Lunar geologic timescale
The lunar geological timescale divides the history of Earth's Moon into five generally recognized periods: the Copernican, Eratosthenian, Imbrian , Nectarian, and Pre-Nectarian...

. A landing site near the freshly formed Cone crater was chosen, as this crater served as a 'natural drill hole' to allow the astronauts to obtain Imbrium ejecta, the primary objective of the mission.

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