Exploration of the Moon

Apollo 12 lunar module Intrepid prepares to descend towards the surface of the Moon. NASA photo.

The physical exploration of the Moon began when Luna 2, a space probe launched by the Soviet Union, made an impact on the surface of the Moon on September 14, 1959. Prior to that the only available means of exploration had been observation. The invention of the optical telescope brought about the first leap in the quality of lunar observations. Galileo Galilei is generally credited as the first person to use a telescope for astronomical purposes; having made his own telescope in 1609, the mountains and craters on the lunar surface were among his first observations using it.

In 1969, Project Apollo first successfully landed people on the Moon. They placed scientific experiments there and returned rocks and data that suggested the Moon is of a similar composition to the Earth.

Early history

In the philosophy of Aristotle, the heavens, starting at the Moon, were the realm of perfection, the sublunary region was the realm of change and corruption, and any resemblance between these regions was strictly ruled out. Aristotle himself suggested that the Moon partook perhaps of some contamination from the realm of corruption.^[1] In his little book On the Face in the Moon's Orb, Plutarch expressed rather different views on the relationship between the Moon and Earth. He suggested that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms. He also entertained the possibility that the Moon was inhabited. It had been suggested already in antiquity that the Moon was a perfect mirror and that its markings were reflections of earthly features, but this explanation was easily dismissed because the face of the Moon never changes as it moves about the Earth.^[1] The explanation that finally became standard was that there were variations of "density" in the Moon that caused this otherwise perfectly spherical body to appear the way it does.^[1] The perfection of the Moon, and therefore the heavens, was thus preserved.

The medieval followers of Aristotle, in the Islamic world and then in Christian Europe, tried to make sense of the lunar spots in Aristotelian terms.^[1] Thomas Harriot, as well as Galilei, drew the first telescopic representation of the Moon and observed it for several years. His drawings, however, remained unpublished.^[1] The first map of the Moon was made by the Belgian cosmographer and astronomer Michael Florent van Langren in 1645.^[1] Two years later a much more influential effort was published by Johannes Hevelius. In 1647 Hevelius published Selenographia, the first treatise entirely devoted to the Moon. Hevelius's nomenclature, although used in Protestant countries until the eighteenth century, was replaced by the system published in 1651 by the Jesuit astronomer Giovanni Battista Riccioli, who gave the large naked-eye spots the names of seas and the telescopic spots (now called craters) the name of philosophers and astronomers.^[1] In 1753 the Croatian Jesuit and astronomer Roger Joseph Boscovich discovered the absence of atmosphere on the Moon. In 1824 Franz von Gruithuisen explained the formation of craters as a result of meteorite strikes.^[2]

Space race

Lunokhod 1

The Cold War-inspired space race between the Soviet Union and the United States of America accelerated with a focus on the Moon. This included many scientifically important firsts, such as the first photographs of the then-unseen far side of the Moon in 1959 by the Soviet Union, and culminated with the landing of the first humans on the Moon in 1969, widely seen around the world as one of the pivotal events of the 20th century, and indeed of human history in general.

Landing map of Apollo, Surveyor and Luna missions.

Apollo 17 astronaut Harrison Schmitt standing next to a boulder at Taurus-Littrow during the third EVA (extravehicular activity). NASA photo.

The first man-made object to reach the Moon was the unmanned Soviet probe Luna 2, which made a hard landing on September 14, 1959, at 21:02:24 Z. The far side of the Moon was first photographed on October 7, 1959 by the Soviet probe Luna 3. In an effort to compete with these Soviet successes, U.S. President John F. Kennedy proposed the national goal of landing a man on the Moon. Speaking to a Joint Session of Congress on May 25, 1961, he said

"First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the earth. No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space."^[3]

The Soviets nonetheless remained in the lead for some time. Luna 9 was the first probe to soft land on the Moon and transmit pictures from the Lunar surface on February 3, 1966. It was proven that a lunar lander would not sink into a thick layer of dust, as had been feared. The first artificial satellite of the Moon was the Soviet probe Luna 10 (launched March 31, 1966). One of the main impediments to human exploration of the Moon was development of adequate heat shield technology to permit atmospheric re-entry without completely burning up a manned spacecraft. The U.S. gained early supremacy in this field through NASA research in thermogravimetric experiments in hypersonic wind tunnels.

On December 24, 1968, the crew of Apollo 8, Frank Borman, James Lovell and William Anders, became the first human beings to enter lunar orbit and see the far side of the Moon with their own eyes. Humans first landed on the Moon on July 20, 1969. The first man to walk on the lunar surface was Neil Armstrong, commander of the U.S. mission Apollo 11. The first robot lunar rover to land on the Moon was the Soviet vessel Lunokhod 1 on November 17, 1970 as part of the Lunokhod program. To date, the last man to stand on the Moon was Eugene Cernan, who as part of the mission Apollo 17 walked on the Moon in December 1972. See also: A full list of lunar Apollo astronauts.

Moon rock samples were brought back to Earth by three Luna missions (Luna 16, 20, and 24) and the Apollo missions 11 through 17 (excepting Apollo 13, which aborted its planned lunar landing).

From the mid-1960s to the mid-1970s there were 65 Moon landings (with 10 in 1971 alone), but after Luna 24 in 1976 they suddenly stopped. The Soviet Union started focusing on Venus and space stations and the U.S. on Mars and beyond.

Recent exploration

In 1990 Japan visited the Moon with the Hiten spacecraft, becoming the third country to place an object in orbit around the Moon. The spacecraft released the Hagoromo probe into lunar orbit, but the transmitter failed, thereby preventing further scientific use of the mission. In September 2007, Japan launched the SELENE spacecraft, with the objectives "to obtain scientific data of the lunar origin and evolution and to develop the technology for the future lunar exploration", according to the JAXA official website.^[4]

NASA launched the Clementine mission in 1994, and Lunar Prospector in 1998.

The European Space Agency launched a small, low-cost lunar orbital probe called SMART 1 on September 27, 2003. SMART 1's primary goal was to take three-dimensional X-ray and infrared imagery of the lunar surface. SMART 1 entered lunar orbit on November 15, 2004 and continued to make observations until September 3, 2006, when it was intentionally crashed into the lunar surface in order to study the impact plume.^[5]

The People's Republic of China has begun the Chang'e program for exploring the Moon and is investigating the prospect of lunar mining, specifically looking for the isotope helium-3 for use as an energy source on Earth.^[6] China launched the Chang'e 1 robotic lunar orbiter on October 24, 2007.

India's national space agency, Indian Space Research Organization (ISRO), launched Chandrayaan-1, an unmanned lunar orbiter, on October 22, 2008.^[7] The lunar probe was originally intended to orbit the Moon for two years, with scientific objectives to prepare a three-dimensional atlas of the near and far side of the Moon and to conduct a chemical and mineralogical mapping of the lunar surface.^[8][9] The unmanned Moon Impact Probe landed on the Moon at 15:04 GMT on November 14, 2008 ^[10] making India the fourth country to touch down on the lunar surface. Unfortunately, Chandrayaan-1 suffered from a star sensor failure and problems with overheating of the craft ultimately leading to a complete loss of signal and early termination of the mission 10 months in.

Water discovered on moon

Speculation is rife among space scientists that the quest for water on the moon may have reached a climactic end with the discovery of “a lot of water” by an instrument on board Chandrayaan-I.

A report by the online space news portal, Space Ref, says this discovery, made by the Moon Mineralogy Mapper (developed by the National Aeronautics and Space Administration) on board the Indian mission, will be the subject of a press conference, to be addressed by Carle Pieters, planetary geologist and principal investigator of the instrument, at the NASA headquarters on Thursday.

The Moon Mineralogy Mapper (M3), an imaging spectrometer, was one of the 11 instruments on board Chandrayaan-I that came to a premature end on August 29. M3 was aimed at providing the first mineral map of the entire lunar surface.

Hinting at this exciting development, a recent report published by Nature News says: “Results soon to be published… will show detailed spectra confirming that, indeed, the polar regions of the moon are chockfull of water-altered minerals.”

Lunar scientists have for decades contended with the possibility of water repositories. They are now increasingly “confident that the decades-long debate is over,” the report says. “The moon, in fact, has water in all sorts of places; not just locked up in minerals, but scattered throughout the broken-up surface, and, potentially, in blocks or sheets of ice at depth.” The results from the NASA’s Lunar Reconnaissance Orbiter are also “offering a wide array of watery signals.”These signals may hold key to life support on moon.^[11][12][13]

According to Indian Space Research Organisation (ISRO) officials, they were well aware of the fact of existence of water on moon just 22 days after Chandrayaan-1 launch but they didn't want to make it public prematurely.^{[citation needed]}

How The Moon Produces Its Own Water

The Moon is a big sponge that absorbs electrically charged particles given out by the Sun. These particles interact with the oxygen present in some dust grains on the lunar surface, producing water. This discovery, made by the ESA-ISRO instrument SARA onboard the Indian Chandrayaan-1 lunar orbiter, confirms how water is likely being created on the lunar surface.

It also gives scientists an ingenious new way to take images of the Moon and any other airless body in the Solar System.

The lunar surface is a loose collection of irregular dust grains, known as regolith. Incoming particles should be trapped in the spaces between the grains and absorbed. When this happens to protons they are expected to interact with the oxygen in the lunar regolith to produce hydroxyl and water.

The signature for these molecules was recently found and reported by Chandrayaan-1's Moon Mineralogy Mapper (M3) instrument team.

The SARA results confirm that solar hydrogen nuclei are indeed being absorbed by the lunar regolith but also highlight a mystery: not every proton is absorbed. One out of every five rebounds into space. In the process, the proton joins with an electron to become an atom of hydrogen. "We didn't expect to see this at all," says Stas Barabash, Swedish Institute of Space Physics, who is the European Principal Investigator for the Sub-keV Atom Reflecting.

Although Barabash and his colleagues do not know what is causing the reflections, the discovery paves the way for a new type of image to be made. The hydrogen shoots off with speeds of around 200 km/s and escapes without being deflected by the Moon's weak gravity.

Hydrogen is also electrically neutral, and is not diverted by the magnetic fields in space. So the atoms fly in straight lines, just like photons of light. In principle, each atom can be traced back to its origin and an image of the surface can be made. The areas that emit most hydrogen will show up the brightest.

Whilst the Moon does not generate a global magnetic field, some lunar rocks are magnetised. Barabash and his team are currently making images, to look for such 'magnetic anomalies' in lunar rocks. These generate magnetic bubbles that deflect incoming protons away into surrounding regions making magnetic rocks appear dark in a hydrogen image.

The incoming protons are part of the solar wind, a constant stream of particles given off by the Sun. They collide with every celestial object in the Solar System but are usually stopped by the body's atmosphere.

On bodies without such a natural shield, for example asteroids or the planet Mercury, the solar wind reaches the ground. The SARA team expects that these objects too will reflect many of the incoming protons back into space as hydrogen atoms.

This knowledge provides timely advice for the scientists and engineers who are readying ESA's BepiColombo mission to Mercury. The spacecraft will be carrying two similar instruments to SARA and may find that the inner-most planet is reflecting more hydrogen than the Moon because the solar wind is more concentrated closer to the Sun.^[14]

NASA's LCROSS mission to hit the surface of moon successful

NASA planned to hit the surface of moon with its impactor probe weighing 2.5 tonnes with a velocity of 9000kmph.It was done deliberately to scatter 350 tonnes of dust. Another probe took the reading of the dust so as to confirm the news of discovery of water of moon. After about 4 minutes it also crashed on the moon's surface. In November, 2009, the LCROSS team at NASA publicly announced the results of the mission. It was discovered that "a few hundred kilograms" of water ice were displaced by the impactor and detected by the probe.

Future plans

Chang'e 2 spacecraft

On January 14, 2004, US President George W. Bush announced the Vision for Space Exploration, a plan leading to new manned lunar missions by 2020. NASA's plan to accomplish that goal was announced on March 19, 2005,^[15] and was promptly dubbed "Apollo 2.0" by critics. NASA launched a preliminary unmanned mission, the Lunar Reconnaissance Orbiter, on June 18, 2009. LRO will take high resolution imagery of the Moon's surface and carries the Lunar Crater Observation and Sensing Satellite (LCROSS), which will investigate the possible existence of water in Shackleton crater.

China plans to land a rover on the Moon in 2012, and to conduct a sample return mission in 2017, and has expressed interest in a manned Moon landing.

India expects to launch another indigenous lunar mission by 2010/11 which would place a motorized rover on the surface of the Moon to collect samples of its soil and conduct experiments.The rover would also dig the moon in search of water.ISRO also plans to undertake a manned spaceflight by 2014 and a manned mission to the Moon by the year 2020.^[16]

Japanese Aerospace Exploration Agency (JAXA) plans a manned lunar landing around 2020 that would lead to a manned lunar base by 2030; however, there is no budget yet for this project.^[17]

Russia also announced to resume its previously frozen project Luna-Glob, an unmanned lander and orbiter, which is slated to launch in 2012.^[18]

Germany also announced in March 2007 that it will launch a national lunar orbiter, LEO in 2012.^[19] however the mission was cancelled due to budgetary constraints.^[20]

In August 2007, NASA stated that all future missions and explorations of the Moon will be done entirely using the metric system. This was done to improve cooperation with space agencies of other countries which already use the metric system.^[21]

The European Space Agency has also announced its intention to send a manned mission to the Moon, as part of the Aurora programme.

On September 13, 2007, the X Prize Foundation, in concert with Google, Inc., announced the Google Lunar X Prize. This contest requires competitors "to land a privately funded robotic rover on the Moon that is capable of completing several mission objectives, including roaming the lunar surface for at least 500 meters and sending video, images and data back to the Earth."^[22]

See also

• List of artificial objects on the Moon
• Moon landing
• Project Apollo
• Robotic exploration of the Moon
• Helium-3

References

External links

Wikimedia Commons has media related to: Moon missions

• Lunar mission timeline - NASA
• Recent Lunar missions - NASA

v • d • e Manned lunar spacecraft Orbiters Apollo Command/Service Module · Zond (Soyuz 7K-L1) · LOK (Soyuz 7K-L3) · Orion · Rus Landers Apollo Lunar Module · Lunniy Korabl · Altair

v • d • e Robotic exploration of the Moon Programs Pioneer · Luna · Ranger · Zond · Surveyor · Lunar Orbiter · Lunokhod · Chinese Lunar Exploration Program · Lunar Precursor Robotic Program Orbiters Explorer 35 · Hiten · Clementine · Lunar Prospector · SMART-1 · Kaguya (Okina · Ouna) · Chang'e 1 · Chandrayaan-1 · Lunar Reconnaissance Orbiter Planned Luna-Glob 1 · GRAIL · LADEE · Chang'e 2 · Chandrayaan-2 · Luna-Glob 1 · ILN Node 1 · ILN Node 2 Proposed Selene-2 · MoonLITE · MoonRaker · Chang'e 3 · Luna-Glob 2 · Google Lunar X Prize · ILN Node 3 · ILN Node 4 · Chang'e 4 Flybys Luna 1 · Luna 3 · Nozomi · Galileo · Cassini–Huygens Impactors Luna 2 · MIP · LCROSS Cancelled LUNAR-A · Lunar Observer · LEO See also Moon · Exploration of the Moon · Colonization of the Moon · Manned lunar spacecraft · List of artificial objects on the Moon Bold italics indicates active missions

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