The Apollo program known as Project Apollo, was the third United States human spaceflight program carried out by the National Aeronautics and Space Administration, which succeeded in landing the first humans on the Moon from 1969 to 1972. First conceived during Dwight D. Eisenhower's administration as a three-man spacecraft to follow the one-man Project Mercury which put the first Americans in space, Apollo was dedicated to President John F. Kennedy's national goal of "landing a man on the Moon and returning him safely to the Earth" by the end of the 1960s, which he proposed in an address to Congress on May 25, 1961, it was the third US human spaceflight program to fly, preceded by the two-man Project Gemini conceived in 1961 to extend spaceflight capability in support of Apollo. Kennedy's goal was accomplished on the Apollo 11 mission when astronauts Neil Armstrong and Buzz Aldrin landed their Apollo Lunar Module on July 20, 1969, walked on the lunar surface, while Michael Collins remained in lunar orbit in the command and service module, all three landed safely on Earth on July 24.
Five subsequent Apollo missions landed astronauts on the Moon, the last in December 1972. In these six spaceflights, twelve men walked on the Moon. Apollo ran from 1961 to 1972, with the first manned flight in 1968, it achieved its goal of manned lunar landing, despite the major setback of a 1967 Apollo 1 cabin fire that killed the entire crew during a prelaunch test. After the first landing, sufficient flight hardware remained for nine follow-on landings with a plan for extended lunar geological and astrophysical exploration. Budget cuts forced the cancellation of three of these. Five of the remaining six missions achieved successful landings, but the Apollo 13 landing was prevented by an oxygen tank explosion in transit to the Moon, which destroyed the service module's capability to provide electrical power, crippling the CSM's propulsion and life support systems; the crew returned to Earth safely by using the lunar module as a "lifeboat" for these functions. Apollo used Saturn family rockets as launch vehicles, which were used for an Apollo Applications Program, which consisted of Skylab, a space station that supported three manned missions in 1973–74, the Apollo–Soyuz Test Project, a joint US-Soviet Union Earth-orbit mission in 1975.
Apollo set several major human spaceflight milestones. It stands alone in sending manned missions beyond low Earth orbit. Apollo 8 was the first manned spacecraft to orbit another celestial body, while the final Apollo 17 mission marked the sixth Moon landing and the ninth manned mission beyond low Earth orbit; the program returned 842 pounds of lunar rocks and soil to Earth contributing to the understanding of the Moon's composition and geological history. The program laid the foundation for NASA's subsequent human spaceflight capability and funded construction of its Johnson Space Center and Kennedy Space Center. Apollo spurred advances in many areas of technology incidental to rocketry and manned spaceflight, including avionics, telecommunications, computers; the Apollo program was conceived during the Eisenhower administration in early 1960, as a follow-up to Project Mercury. While the Mercury capsule could only support one astronaut on a limited Earth orbital mission, Apollo would carry three astronauts.
Possible missions included ferrying crews to a space station, circumlunar flights, eventual manned lunar landings. The program was named after Apollo, the Greek god of light and the sun, by NASA manager Abe Silverstein, who said that "I was naming the spacecraft like I'd name my baby." Silverstein chose the name at home one evening, early in 1960, because he felt "Apollo riding his chariot across the Sun was appropriate to the grand scale of the proposed program."In July 1960, NASA Deputy Administrator Hugh L. Dryden announced the Apollo program to industry representatives at a series of Space Task Group conferences. Preliminary specifications were laid out for a spacecraft with a mission module cabin separate from the command module, a propulsion and equipment module. On August 30, a feasibility study competition was announced, on October 25, three study contracts were awarded to General Dynamics/Convair, General Electric, the Glenn L. Martin Company. Meanwhile, NASA performed its own in-house spacecraft design studies led by Maxime Faget, to serve as a gauge to judge and monitor the three industry designs.
In November 1960, John F. Kennedy was elected president after a campaign that promised American superiority over the Soviet Union in the fields of space exploration and missile defense. Up to the election of 1960, Kennedy had been speaking out against the "missile gap" that he and many other senators felt had developed between the Soviet Union and United States due to the inaction of President Eisenhower. Beyond military power, Kennedy used aerospace technology as a symbol of national prestige, pledging to make the US not "first but, first and, first if, but first period." Despite Kennedy's rhetoric, he did not come to a decision on the status of the Apollo program once he became president. He knew little about the technical details of the space program, was put off by the massive financial commitment required by a manned Moon landing; when Kennedy's newly appointed NASA Administrator James E. Webb requested a 30 percent budget increase for his agency, Kennedy supported an acceleration of NASA's large booster program but deferred a decision on the broader issue.
On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person to fly in space, reinforcing American fears about being left behind in a technological competition with the Soviet Union. At a meeting of the US House Committee on Science and Astronaut
A world war is a large-scale war which affects the whole world directly or indirectly. World wars span multiple countries on multiple continents or just two countries, with battles fought in many theaters. While a variety of global conflicts have been subjectively deemed "world wars", such as the Cold War and the War on Terror, the term is and accepted only as it is retrospectively applied to two major international conflicts that occurred during the 20th century: World War I and World War II; the Oxford English Dictionary cited the first known usage in the English language to a Scottish newspaper, The People's Journal, in 1848: "A war among the great powers is now a world-war." The term "world war" is used by Karl Marx and his associate, Friedrich Engels, in a series of articles published around 1850 called The Class Struggles in France. Rasmus B. Anderson in 1889 described an episode in Teutonic mythology as a “world war”, justifying this description by a line in an Old Norse epic poem, "Völuspá: folcvig fyrst i heimi" German writer August Wilhelm Otto Niemann had used the term "world war" in the title of his anti-British novel, Der Weltkrieg: Deutsche Träume in 1904, published in English as The Coming Conquest of England.
In English, the term "First World War" had been used by Charles à Court Repington, as a title for his memoirs. The term "World War I" was coined by Time magazine on page 28b of its June 1939 issue. In the same article, on page 32, the term "World War II" was first used speculatively to describe the upcoming war; the first use for the actual war came in its issue of September 11, 1939. One week earlier, on September 4, the day after France and the United Kingdom declared war on Germany, the Danish newspaper Kristeligt Dagblad used the term on its front page, saying "The Second World War broke out yesterday at 11 a.m."Speculative fiction authors had been noting the concept of a Second World War in 1919 and 1920, when Milo Hastings wrote his dystopian novel, City of Endless Night. Other languages have adopted the "world war" terminology, for example. In terms of human technological history, the scale of World War I was enabled by the technological advances of the second industrial revolution and the resulting globalization that allowed global power projection and mass production of military hardware.
Wars on such a scale have not been repeated since the onset of the Atomic Age and the resulting danger of mutually-assured destruction. It had been recognized that the complex system of opposing alliances was to lead to a worldwide conflict if a war broke out. Due to this fact, a minute conflict between two countries had the potential to set off a domino effect of alliances, triggering a world war; the fact that the powers involved had large overseas empires guaranteed that such a war would be worldwide, as the colonies' resources would be a crucial strategic factor. The same strategic considerations ensured that the combatants would strike at each other's colonies, thus spreading the wars far more than those of pre-Columbian times. War crimes were perpetrated in World War I. Chemical weapons were used in the First World War despite the Hague Conventions of 1899 and 1907 having outlawed the use of such weapons in warfare; the Ottoman Empire was responsible for the Armenian genocide, the death of over one million Armenians during the First World War.
The Second World War occurred from 1939 to 1945 and is the only conflict in which atomic bombs have been used. Hiroshima and Nagasaki, in Japan, were devastated by atomic bombs dropped by the United States. Nazi Germany was responsible for genocides, most notably the Holocaust, the killing of six million Jews; the United States, the Soviet Union, Canada deported and interned minority groups within their own borders, because of the conflict, many ethnic Germans were expelled from Eastern Europe. Japan was responsible for attacking neutral nations without a declaration of war, such as the bombing of Pearl Harbor, it is known for its brutal treatment and killing of Allied prisoners of war and the inhabitants of Asia. It used Asians as forced laborers and was responsible for the Nanking massacre where 250,000 civilians in the city were brutally murdered by Japanese troops. Non-combatants suffered at least as badly as or worse than combatants, the distinction between combatants and non-combatants was blurred by belligerents of total war in both conflicts.
The outcome of World War II had a profound effect on the course of world history. The old European empires either collapsed or were dismantled as a direct result of the wars' crushing costs and, in some cases, their fall was due to the defeat of imperial powers; the United States became established as the dominant global superpower, along with its ideological foe, the Soviet Union, in close competition. The two superpowers exerted political influence over most of the world's nation-states for decades after the end of the Second World War; the modern international security and diplomatic system was created in the aftermath of the wars. Institut
Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times. Earth's axis of rotation is tilted with respect to its orbital plane; the gravitational interaction between Earth and the Moon causes ocean tides, stabilizes Earth's orientation on its axis, slows its rotation. Earth is the largest of the four terrestrial planets. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water by oceans; the remaining 29% is land consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere.
The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, a convecting mantle that drives plate tectonics. Within the first billion years of Earth's history, life appeared in the oceans and began to affect the Earth's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms; some geological evidence indicates. Since the combination of Earth's distance from the Sun, physical properties, geological history have allowed life to evolve and thrive. In the history of the Earth, biodiversity has gone through long periods of expansion punctuated by mass extinction events. Over 99% of all species that lived on Earth are extinct. Estimates of the number of species on Earth today vary widely. Over 7.6 billion humans live on Earth and depend on its biosphere and natural resources for their survival.
Humans have developed diverse cultures. The modern English word Earth developed from a wide variety of Middle English forms, which derived from an Old English noun most spelled eorðe, it has cognates in every Germanic language, their proto-Germanic root has been reconstructed as *erþō. In its earliest appearances, eorðe was being used to translate the many senses of Latin terra and Greek γῆ: the ground, its soil, dry land, the human world, the surface of the world, the globe itself; as with Terra and Gaia, Earth was a personified goddess in Germanic paganism: the Angles were listed by Tacitus as among the devotees of Nerthus, Norse mythology included Jörð, a giantess given as the mother of Thor. Earth was written in lowercase, from early Middle English, its definite sense as "the globe" was expressed as the earth. By Early Modern English, many nouns were capitalized, the earth became the Earth when referenced along with other heavenly bodies. More the name is sometimes given as Earth, by analogy with the names of the other planets.
House styles now vary: Oxford spelling recognizes the lowercase form as the most common, with the capitalized form an acceptable variant. Another convention capitalizes "Earth" when appearing as a name but writes it in lowercase when preceded by the, it always appears in lowercase in colloquial expressions such as "what on earth are you doing?" The oldest material found in the Solar System is dated to 4.5672±0.0006 billion years ago. By 4.54±0.04 Bya the primordial Earth had formed. The bodies in the Solar System evolved with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, the planets grow out of that disk with the Sun. A nebula contains gas, ice grains, dust. According to nebular theory, planetesimals formed by accretion, with the primordial Earth taking 10–20 million years to form. A subject of research is the formation of some 4.53 Bya. A leading hypothesis is that it was formed by accretion from material loosed from Earth after a Mars-sized object, named Theia, hit Earth.
In this view, the mass of Theia was 10 percent of Earth, it hit Earth with a glancing blow and some of its mass merged with Earth. Between 4.1 and 3.8 Bya, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of the Moon and, by inference, to that of Earth. Earth's atmosphere and oceans were formed by volcanic outgassing. Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids and comets. In this model, atmospheric "greenhouse gases" kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity. By 3.5 Bya, Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind. A crust formed; the two models that explain land mass propose either a steady growth to the present-day forms or, more a rapid growth early in Earth history followed by a long-term steady continental area. Continents formed by plate tectonics
Webb is a small lunar impact crater, located near the eastern edge of the Mare Fecunditatis, in the eastern part of the Moon near the equator. It was named after British astronomer Thomas William Webb, it is to the north of the prominent crater Langrenus, west of Maclaurin. The interior of Webb is dark compared with the inner walls of the rim, it has a low hill at the midpoint of the interior. On the lunar mare to the north is a faint marking of a ray system that appears to radiate from this crater. West of the crater is the wrinkle ridge Dorsa Andrusov. By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint, closest to Webb; the following craters have been renamed by the IAU. Webb R — See Condon. Asteroid 3041 Webb
Asteroids are minor planets of the inner Solar System. Larger asteroids have been called planetoids; these terms have been applied to any astronomical object orbiting the Sun that did not resemble a planet-like disc and was not observed to have characteristics of an active comet such as a tail. As minor planets in the outer Solar System were discovered they were found to have volatile-rich surfaces similar to comets; as a result, they were distinguished from objects found in the main asteroid belt. In this article, the term "asteroid" refers to the minor planets of the inner Solar System including those co-orbital with Jupiter. There exist millions of asteroids, many thought to be the shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets; the vast majority of known asteroids orbit within the main asteroid belt located between the orbits of Mars and Jupiter, or are co-orbital with Jupiter. However, other orbital families exist with significant populations, including the near-Earth objects.
Individual asteroids are classified by their characteristic spectra, with the majority falling into three main groups: C-type, M-type, S-type. These were named after and are identified with carbon-rich and silicate compositions, respectively; the sizes of asteroids varies greatly. Asteroids are differentiated from meteoroids. In the case of comets, the difference is one of composition: while asteroids are composed of mineral and rock, comets are composed of dust and ice. Furthermore, asteroids formed closer to the sun; the difference between asteroids and meteoroids is one of size: meteoroids have a diameter of one meter or less, whereas asteroids have a diameter of greater than one meter. Meteoroids can be composed of either cometary or asteroidal materials. Only one asteroid, 4 Vesta, which has a reflective surface, is visible to the naked eye, this only in dark skies when it is favorably positioned. Small asteroids passing close to Earth may be visible to the naked eye for a short time; as of October 2017, the Minor Planet Center had data on 745,000 objects in the inner and outer Solar System, of which 504,000 had enough information to be given numbered designations.
The United Nations declared 30 June as International Asteroid Day to educate the public about asteroids. The date of International Asteroid Day commemorates the anniversary of the Tunguska asteroid impact over Siberia, Russian Federation, on 30 June 1908. In April 2018, the B612 Foundation reported "It's 100 percent certain we'll be hit, but we're not 100 percent sure when." In 2018, physicist Stephen Hawking, in his final book Brief Answers to the Big Questions, considered an asteroid collision to be the biggest threat to the planet. In June 2018, the US National Science and Technology Council warned that America is unprepared for an asteroid impact event, has developed and released the "National Near-Earth Object Preparedness Strategy Action Plan" to better prepare. According to expert testimony in the United States Congress in 2013, NASA would require at least five years of preparation before a mission to intercept an asteroid could be launched; the first asteroid to be discovered, was considered to be a new planet.
This was followed by the discovery of other similar bodies, with the equipment of the time, appeared to be points of light, like stars, showing little or no planetary disc, though distinguishable from stars due to their apparent motions. This prompted the astronomer Sir William Herschel to propose the term "asteroid", coined in Greek as ἀστεροειδής, or asteroeidēs, meaning'star-like, star-shaped', derived from the Ancient Greek ἀστήρ astēr'star, planet'. In the early second half of the nineteenth century, the terms "asteroid" and "planet" were still used interchangeably. Overview of discovery timeline: 10 by 1849 1 Ceres, 1801 2 Pallas – 1802 3 Juno – 1804 4 Vesta – 1807 5 Astraea – 1845 in 1846, planet Neptune was discovered 6 Hebe – July 1847 7 Iris – August 1847 8 Flora – October 1847 9 Metis – 25 April 1848 10 Hygiea – 12 April 1849 tenth asteroid discovered 100 asteroids by 1868 1,000 by 1921 10,000 by 1989 100,000 by 2005 ~700,000 by 2015 Asteroid discovery methods have improved over the past two centuries.
In the last years of the 18th century, Baron Franz Xaver von Zach organized a group of 24 astronomers to search the sky for the missing planet predicted at about 2.8 AU from the Sun by the Titius-Bode law because of the discovery, by Sir William Herschel in 1781, of the planet Uranus at the distance predicted by the law. This task required that hand-drawn sky charts be prepared for all stars in the zodiacal band down to an agreed-upon limit of faintness. On subsequent nights, the sky would be charted again and any moving object would be spotted; the expected motion of the missing planet was about 30 seconds of arc per hour discernible by observers. The first object, was not discovered by a member of the group, but rather by accident in 1801 by Giuseppe Piazzi, director of the observatory of Palermo in Sicily, he discovered a new star-like object in Taurus and followed the displacement of this object during several nights. That year, Carl Friedrich Gauss used these observations to calculate the orbit of this unknown object, found to be between the planets Mars and Jupiter.
Piazzi named it after Ceres, the Roman goddess of agriculture. Three other asteroids (2 Pallas, 3 Juno, 4 Ves
Clementine was a joint space project between the Ballistic Missile Defense Organization and NASA. Launched on January 25, 1994, the objective of the mission was to test sensors and spacecraft components under extended exposure to the space environment and to make scientific observations of the Moon and the near-Earth asteroid 1620 Geographos; the Geographos observations were not made due to a malfunction in the spacecraft. The lunar observations made included imaging at various wavelengths in the visible as well as in ultraviolet and infrared, laser ranging altimetry and charged particle measurements; these observations were for the purposes of obtaining multi-spectral imaging of the entire lunar surface, assessing the surface mineralogy of the Moon, obtaining altimetry from 60N to 60S latitude, obtaining gravity data for the near side. There were plans to image and determine the size, rotational characteristics, surface properties, cratering statistics of Geographos. Clementine carried seven distinct experiments on-board: a UV/Visible Camera, a Near Infrared Camera, a Long Wavelength Infrared Camera, a High Resolution Camera, two Star Tracker Cameras, a Laser Altimeter, a Charged Particle Telescope.
The S-band transponder was used for communications and the gravimetry experiment. The project was named Clementine after the song "Oh My Darling, Clementine" as the spacecraft would be "lost and gone forever" following its mission; the spacecraft was an octagonal prism 1.88 m high and 1.14 m across with two solar panels protruding on opposite sides parallel to the axis of the prism. A 42-inch-diameter high-gain fixed dish antenna was at one end of the prism, the 489 N thruster at the other end; the sensor openings were all located together on one of the eight panels, 90 degrees from the solar panels, protected in by a single sensor cover. The spacecraft propulsion system consisted of a monopropellant hydrazine system for attitude control and a bipropellant nitrogen tetroxide and monomethyl hydrazine system for the maneuvers in space; the bipropellant system had a total Delta-v capability of about 1,900 m/s with about 550 m/s required for lunar insertion and 540 m/s for lunar departure. Attitude control was achieved with 12 small attitude control jets, two star tracker, two inertial measurement units.
The spacecraft was three-axis stabilized in lunar orbit via reaction wheels with a precision of 0.05 deg in control and 0.03 deg in knowledge. Power was provided by gimbaled, single axis, GaAs/Ge solar panels which charged a 15 A·h, 47 W·h/kg Nihau common pressure vessel battery. Spacecraft data processing was performed using a MIL-STD-1750A computer for savemode, attitude control, housekeeping operations, a RISC 32-bit processor for image processing and autonomous operations, an image compression system provided by the French Space Agency CNES. A data handling unit sequenced the cameras, operated the image compression system, directed the data flow. Data was stored in a 2 Gbit dynamic solid state data recorder. On January 25, 1994, Clementine was launched from Space Launch Complex 4 West at Vandenberg Air Force Base, using a Titan II launch vehicle; the mission had two phases. After two Earth flybys, lunar insertion was achieved one month after launch. Lunar mapping took place over two months, in two parts.
The first part consisted of a five-hour elliptical polar orbit with a periapsis of about 400 km at 13 degrees south latitude and an apoapsis of 8300 km. Each orbit consisted of an 80-minute lunar mapping phase near periapsis and 139 minutes of downlink at apoapsis. After one month of mapping the orbit was rotated to a periapsis at 13 degrees north latitude, where it remained for one more month; this allowed global imaging and altimetry coverage from 60° south to 60° north, over a total of 300 orbits. After an Earth to Moon transfer and two more Earth flybys, the spacecraft was to head for 1620 Geographos, arriving three months for a flyby, with a nominal approach closer than 100 km. On May 7, 1994, after the first Earth transfer orbit, a malfunction aboard the craft caused one of the attitude control thrusters to fire for 11 minutes, using up its fuel supply and causing Clementine to spin at about 80 rpm. Under these conditions, the asteroid flyby could not yield useful results, so the spacecraft was put into a geocentric orbit passing through the Van Allen radiation belts to test the various components on board.
The mission ended in June 1994 when the power level onboard dropped to a point where the telemetry from the spacecraft was no longer intelligible. NASA announced on March 5, 1998, that data obtained from Clementine indicated that there is enough water in polar craters of the Moon to support a human colony and a rocket fueling station; the Charged Particle Telescope on Clementine was designed to measure the flux and spectra of energetic protons and electrons. The primary goals of the investigation were to: study the interaction of the Earth's magnetotail and interplanetary shocks with the Moon. In order to meet the stringent limit on the mass of the instrument, it was implemented as a single element telescope; the telescope had a 10 degree half-angle field of view. The detector, a silicon surface-barrier type with an area of 100
The lunar maria are large, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed 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 composition, hence appear dark to the naked eye. The maria cover about 16% of the lunar surface on the side visible from Earth; the few maria on the far side are much smaller, residing in large craters. The traditional nomenclature for the Moon includes one oceanus, as well as features with the names lacus and sinus; the last three have the same nature and characteristics. The names of maria refer to sea attributes, or states of mind. Mare Humboldtianum and Mare Smythii were established before the final nomenclature, that of states of mind, was accepted, do not follow this pattern; when Mare Moscoviense was discovered by the Luna 3, the name was proposed by the Soviet Union, it was only accepted by the International Astronomical Union with the justification that Moscow is the state of mind.
The ages of the mare basalts have been determined both by direct radiometric dating and by the technique of crater counting. The radiometric ages range from about 3.16 to 4.2 Ga, whereas the youngest ages determined from crater counting are about 1.2 Ga. Nevertheless, the majority of mare basalts appear to have erupted between about 3 and 3.5 Ga. The few basaltic eruptions that occurred on the far side are old, whereas the youngest flows are found within Oceanus Procellarum on the nearside. While many of the basalts either erupted within, or flowed into, low-lying impact basins, the largest expanse of volcanic units, Oceanus Procellarum, does not correspond to any known impact basin. There are many common misconceptions concerning the spatial distribution of mare basalts. Since many mare basalts fill low-lying impact basins, it was once assumed that the impact event itself somehow caused the volcanic eruption. [Note: current data in fact may not preclude this, although the timing and length of mare volcanism in a number of basins cast some doubt on it.
Initial mare volcanism seems to have begun within 100 million years of basin formation. Although these authors felt that 100 million years was sufficiently long that a correlation between impact and volcanism seemed unlikely, there are problems with this argument; the authors point out that the oldest and deepest basalts in each basin are buried and inaccessible, leading to a sampling bias. It is sometimes suggested that the gravity field of the Earth might preferentially allow eruptions to occur on the near side, but not on the far side. However, in a reference frame rotating with the Moon, the centrifugal acceleration the Moon is experiencing is equal and opposite to the gravitational acceleration of the Earth. There is thus no net force directed towards the Earth; the Earth tides do act to deform the shape of the Moon, but this shape is that of an elongated ellipsoid with high points at both the sub- and anti-Earth points. As an analogy, one should remember that there are two high tides per day on Earth, not one.
Since mare basaltic magmas are denser than upper crustal anorthositic materials, basaltic eruptions might be favored at locations of low elevation where the crust is thin. However, the far side South Pole-Aitken basin contains the lowest elevations of the Moon and yet is only sparingly filled by basaltic lavas. In addition, the crustal thickness beneath this basin is predicted to be much smaller than beneath Oceanus Procellarum. While the thickness of the crust might modulate the quantity of basaltic lavas that reach the surface, crustal thickness by itself cannot be the sole factor controlling the distribution of mare basalts, it is suggested that there is some form of link between the synchronous rotation of the Moon about the Earth, the mare basalts. However, gravitational torques that result in tidal despinning only arise from the moments of inertia of the body, the mare basalts hardly contribute to this. Furthermore, tidal despinning is predicted to have occurred whereas the majority of mare basalts erupted about one billion years later.
The reason that the mare basalts are predominantly located on the near-side hemisphere of the Moon is still being debated by the scientific community. Based on data obtained from the Lunar Prospector mission, it appears that a large proportion of the Moon's inventory of heat producing elements is located within the regions of Oceanus Procellarum and the Imbrium basin, a unique geochemical province now referred to as the Procellarum KREEP Terrane. While the enhancement in heat production within the Procellarum KREEP Terrane is most related to the longevity and intensity of volcanism found there, the mechanism by which KREEP became concentrated within this region is not agreed upon. Using terrestrial classification schemes, all mare basalts are classified as tholeiitic, but specific subclassifications have been invented to further describe the population of lunar basalts. Mare basalts are grouped into three series based on their major element chemistry: high-Ti basalts, low-Ti basalts, very-low-Ti