Space exploration is the use of astronomy Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe and space technology "Every day" technologies such as weather forecasting, remote sensing, GPS systems, satellite television, and some long distance communications systems critically rely on space infrastructure. Of sciences astronomy and Earth sciences most notably benefit from space technology to explore outer space Outer space is the void that exists beyond any celestial body including the Earth. It is not completely empty (i.e. a perfect vacuum), but contains a low density of particles, predominantly hydrogen plasma, as well as electromagnetic radiation, magnetic fields, and neutrinos. Theoretically, it also contains dark matter and dark energy.^[1] Physical exploration Exploration is the act of searching or traveling a terrain for the purpose of discovery of resources or information. Exploration occurs in all non-sessile animal species, including humans. In human history, its peak is seen during the Age of Discovery for Europe's contact with the rest of the world, and Major explorations after the Age of of space is conducted both by human spaceflights Human spaceflight is spaceflight with a human crew and possibly passengers. This makes it unlike robotic space probes or remotely-controlled satellites. Human spaceflight is sometimes called manned spaceflight, a term now deprecated by major space agencies in favor of its gender-neutral alternative and by robotic spacecraft A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some. While the observation of objects in space, known as astronomy Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe, predates reliable recorded history Recorded history is a part of human history that has been written down or recorded by the use of language. It starts in the 4th millennium BC, with the invention of writing. The period before this is known as prehistory, it was the development of large liquid-fueled rocket engines A rocket engine or simply "rocket" is a jet engine that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law. Since they need no external material to form their jet, rocket engines can be used for spacecraft propulsion as well as during the early 20th century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, uniting different nations, ensuring the future survival of humanity and developing military and strategic advantages against other countries. Various criticisms of space exploration are sometimes made.

Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War The Cold War was the continuing state of political conflict, military tension, proxy wars, and economic competition existing after World War II (1939–1945), primarily between the Soviet Union and its satellite states, and the powers of the Western world, particularly the United States. Although the primary participants' military forces never. The early era of space exploration was driven by a "Space Race The Space Race was a technological and ideological competition between the Soviet Union and the United States (USA) for supremacy in outer-space exploration during the mid-to-late 20th century. The term refers to a specific period in human history, 1957-1975, and does not include subsequent efforts by these or other nations to explore space. The" between the Soviet Union The Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the Russian: Союз Советских Социалистических Республик (help·info), tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, IPA [sɐˈjʊs sɐˈvʲeʦkʲɪx səʦɪ and the United States ^ b. English is the de facto language of American government and the sole language spoken at home by 80% of Americans age five and older. Spanish is the second most commonly spoken language; the launch of the first man-made object to orbit the Earth Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the World, the Blue Planet,[note 6] or by its Latin name, Terra.[note 7], the USSR's Sputnik 1 Sputnik 1 Russian: "Спутник-1" Russian pronunciation: [ˈsputnʲɪk], "Satellite-1", ПС-1 ) was the first Earth-orbiting artificial satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957, and was the first in a series of satellites collectively known as the Sputnik program, on October 4, 1957, and the first Moon The Moon is Earth's only natural satellite[nb 4] and is the fifth largest satellite in the Solar System. It is the largest natural satellite in the Solar System relative to the size of its planet, a quarter the diameter of Earth and 1/81 its mass, and is the second densest satellite after Io. It is in synchronous rotation with Earth, always landing by the American Apollo 11 The Apollo 11 space flight landed the first humans on Earth's Moon on July 20, 1969. The mission, carried out by the United States, is considered a major accomplishment in human exploration and represented a victory by the U.S. in the Cold War Space Race with the Soviet Union craft on July 20, 1969 are often taken as the boundaries for this initial period. The Soviet space program The Soviet space program refers to the rocketry and space exploration programs conducted by the Soviet Union from the 1930s until its dissolution in 1991. Over its sixty-year history, this primarily classified military program was responsible for a number of notable accomplishments in space flight, including mankind's first intercontinental achieved many of the first milestones, including the first living being in orbit in 1957, the first human spaceflight Human spaceflight is spaceflight with a human crew and possibly passengers. This makes it unlike robotic space probes or remotely-controlled satellites. Human spaceflight is sometimes called manned spaceflight, a term now deprecated by major space agencies in favor of its gender-neutral alternative (Yuri Gagarin Yuri Alekseyevich Gagarin , Hero of the Soviet Union, was a Soviet cosmonaut. On 12 April 1961, he became the first human in outer space and the first to orbit the Earth. He received medals from around the world for his pioneering tour in space aboard Vostok 1 Vostok 1 was the first human spaceflight. The Vostok 3KA spacecraft was launched on April 12, 1961, taking into space Yuri Gagarin, a cosmonaut from the Soviet Union. The Vostok 1 mission was the first time anyone had journeyed into outer space and the first time anyone had entered into orbit. The Vostok 1 was launched by the Soviet space program) in 1961, the first spacewalk Extra-vehicular activity is work done by an astronaut away from the Earth, and outside of a spacecraft. The term most commonly applies to an EVA made outside a craft orbiting Earth (a spacewalk), but also applies to an EVA made on the surface of the Moon (a moonwalk). In the later lunar landing missions (Apollo 15, 16, and 17) the command module (by Aleksei Leonov Alexey Arkhipovich Leonov is a retired Soviet/Russian cosmonaut and Air Force General who, on March 18, 1965, became the first human to conduct a space walk) in 1965, the first automatic landing Luna 9 (internal name E-6 N. 13) was an unmanned space mission of the Soviet Union's Luna program. On February 3, 1966 the Luna 9 spacecraft was the first spacecraft to achieve a soft landing on any planetary body other than Earth and to transmit photographic data to Earth on another celestial body in 1966, and the launch of the first space station To date, only low earth orbital stations have been implemented, otherwise known as orbital stations. A space station is distinguished from other manned spacecraft by its lack of major propulsion or landing facilities—instead, other vehicles are used as transport to and from the station. Current and recent-history space stations are designed for (Salyut 1 Salyut 1 (Russian: Салют-1; English translation: Salute 1) was the first space station of any kind, launched by the USSR on April 19, 1971. It was launched unmanned using a Proton-K rocket. Its first crew came later in Soyuz 10, but was unable to dock completely; its second crew launched in Soyuz 11 and remained on board for 23 days. However,) in 1971.

After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the Space Shuttle program NASA's Space Shuttle, officially called Space Transportation System , is the United States government's current manned launch vehicle. The winged Space Shuttle orbiter is launched vertically, usually carrying five to seven astronauts (although eight have been carried) and up to 50,000 lb (22 700 kg) of payload into low earth orbit. When its, and from competition to cooperation as with the International Space Station The International Space Station is an internationally developed research facility that is being assembled in low Earth orbit. On-orbit construction of the station began in 1998 and is scheduled for completion by late 2011. The station is expected to remain in operation until at least 2015, and likely 2020. With a greater mass than that of any.

From the 1990s onwards, private interests began promoting space tourism Space tourism is tourism in which participants pay for flights into space. As of 2010, orbital space tourism opportunities are limited and expensive, with only the Russian Space Agency providing transport. The price for a flight brokered by Space Adventures to the International Space Station aboard a Soyuz spacecraft is US$ 20–35 million. The and then private space exploration of the Moon (see GLXP The Google Lunar X Prize, sometimes referred to as simply Moon 2.0, is a space competition organized by the X Prize Foundation, and sponsored by Google. It was announced at the Wired Nextfest on 13 September 2007. The challenge calls for privately ).

In the 2000s, China b. ^ Simple characterizations of the political structure since the 1980s are no longer possible initiated a successful manned spaceflight program The space program of the People's Republic of China is currently directed by the CNSA. Its technological roots can be traced back to the late 1950s, when China began a rudimentary ballistic missile program in response to perceived American threats. However, the first Chinese manned flight program only began in earnest several decades later, when a, while the European Union The European Union is an economic and political union of 27 member states which are located primarily in Europe. Committed to regional integration, the EU was established by the Treaty of Maastricht in 1993 upon the foundations of the European Communities. With over 500 million citizens, the EU combined generated an estimated 28% share (US$ 16.5, Japan Japan is an island country in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south. The characters that make up Japan's name mean "sun-origin", which is why Japan is, and India India, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with 1.18 billion people, and the most populous democracy in the world. Mainland India is bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal on the have also planned future manned space missions. The United States has committed to return to the Moon by 2018 and later Mars.^[2][3][4] China, Russia, Japan, and India have advocated manned missions to the Moon during the 21st century, while the European Union has advocated manned missions to both the Moon and Mars The Aurora programme is a human spaceflight programme of the European Space Agency established in 2001 with the primary objectives of creating, and then implementing, a European long-term plan for exploration of the Solar System using robotic spacecraft and human spaceflight. A secondary objective is to search for life beyond the Earth during the 21st century.^[5]

Contents 1 History of exploration in the 20th Century 2 Future of space exploration 3 Targets of exploration 3.1 Astrobiology 3.2 The Sun 3.3 Mercury 3.4 Venus 3.5 Earth 3.6 Earth's Moon 3.7 Mars 3.7.1 Photos 3.8 Jupiter 3.9 Saturn 3.10 Uranus 3.11 Neptune 3.12 Dwarf planets 3.12.1 Pluto 3.12.2 Eris 3.12.3 Ceres 3.13 Asteroids 4 Rationales 5 Opposition 6 Related topics 6.1 Spaceflight 6.2 Satellites 6.3 Militarization of space 6.4 Space colonization 7 See also 8 References 9 External links

History of exploration in the 20th Century

See also: Timeline of space exploration , Astronomy#History Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation). It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe , and Timeline of first orbital launches by country This is a timeline of first orbital launches by country. While a number of countries have built satellites, as of 2009, nine countries historically have developed the capability to send objects into orbit using their own launch vehicles. In addition, Russia and Ukraine inherited the space launchers and satellites capability from the Soviet Union, Most orbital flight actually takes place in upper layers of the atmosphere, especially in the thermosphere (not to scale) In July 1950 the first bumper rocket launches from Cape Canaveral, Florida launched; the Bumper After a July 1946 suggestion by Colonel Holger N. Toftoy to combine the V-2 rocket and Wac Corporal, the US Bumper Program was inaugurated on June 20, 1947: was a two-stage rocket. It topped a V-2 missile The V-2 rocket , technical name A4, was a long range ballistic missile that was developed by the end of the Second World War in Nazi Germany. The rocket was the world's first long-range combat-ballistic missile and first human artifact to achieve sub-orbital spaceflight. It was the progenitor of all modern rockets base with a WAC Corporal The WAC or WAC Corporal was the first sounding rocket developed in the United States. Begun as a spinoff of the Corporal program, the WAC was a "little sister" to the larger Corporal. It was designed and built jointly by the Douglas Aircraft Company and the Guggenheim Aeronautical Laboratory rocket. It could reach then-record altitudes of almost 400 km. Launched by General Electric Company, this Bumper was used primarily for testing rocket systems and for research on the upper atmosphere . Bumper rockets carried small payloads that allowed them to measure attributes including air temperature and cosmic ray impacts.

The first steps into space were taken by German scientists during World War II Albania · Australia · Austria · Azerbaijan · Belarus · Belgium · Brazil · Bulgaria · Burma · Cambodia · Canada · Ceylon (Sri Lanka) · Channel Islands · China · Czechoslovakia · Denmark · Dutch East Indies · Egypt · Estonia · Finland · France · Germany · Gibraltar · Greece · Greenland · Hong Kong · Hungary · Iceland · while testing the V2 rocket The V-2 rocket , technical name A4, was a long-range ballistic missile that was developed at the beginning of the Second World War in Nazi Germany, specifically targeted at Belgium and sites in southeastern England. The rocket was the world's first long-range combat-ballistic missile and first human artifact to achieve sub-orbital spaceflight. It which became the first human-made object in space. After the war, the Allies used German scientists Operation Paperclip was the Office of Strategic Services program used to recruit the scientists of Nazi Germany for employment by the United States in the aftermath of World War II (1939–45). It was executed by the Joint Intelligence Objectives Agency (JIOA), and in the context of the burgeoning Soviet–American Cold War (1945–91), one and their captured rockets in programs for both military and civilian research. The first scientific exploration from space was the cosmic radiation experiment launched by the U.S. on a V2 rocket on May 10, 1946. The first images of Earth taken from space followed the same year while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V2s launched by Americans. These suborbital experiments only allowed a very short time in space which limited their usefulness.

First orbital flights

Sputnik 1 Sputnik 1 Russian: "Спутник-1" Russian pronunciation: [ˈsputnʲɪk], "Satellite-1", ПС-1 ) was the first Earth-orbiting artificial satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957, and was the first in a series of satellites collectively known as the Sputnik program, the first artificial satellite In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon orbited earth at 939 km (583 mi) to 215 km (134 mi) in 1957, and was soon followed by Sputnik 2 Sputnik 2 was the second spacecraft launched into Earth orbit, on November 3, 1957, and the first to carry a living animal, a dog named Laika. Sputnik 2 was a 4-meter (13 foot) high cone-shaped capsule with a base diameter of 2 meters (6.6 feet). It contained several compartments for radio transmitters, a telemetry system, a programming unit, a. See First satellite by country In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon (Replica Pictured)

The first successful orbital launch was of the Soviet The Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the Russian: Союз Советских Социалистических Республик (help·info), tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, IPA [sɐˈjʊs sɐˈvʲeʦkʲɪx səʦɪ unmanned Sputnik ("Satellite I") Sputnik 1 Russian: "Спутник-1" Russian pronunciation: [ˈsputnʲɪk], "Satellite-1", ПС-1 ) was the first Earth-orbiting artificial satellite. It was launched into an elliptical low Earth orbit by the Soviet Union on 4 October 1957, and was the first in a series of satellites collectively known as the Sputnik program mission on October 4, 1957. The satellite weighed about 83 kg (184 pounds), and is believed to have orbited Earth at a height of about 250 km (150 miles). It had two radio transmitters (20 and 40 MHz), which emitted "beeps" that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on January 3, 1958.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch Vanguard 1 into orbit two months later. On January 31, 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket. In the meantime, the Soviet dog Laika became the first animal in orbit on November 3, 1957.

First human flights

The first successful human spaceflight was Vostok 1 ("East 1"), carrying 27 year old Russian cosmonaut Yuri Gagarin on April 12, 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin's flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era in space exploration: human spaceflight.

Yuri Gagarin, the first person to make an orbital flight of Earth

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard's suborbital flight in Mercury-Redstone 3. Orbital flight was achieved by the United States when John Glenn's Mercury-Atlas 6 orbited the Earth on February 20, 1962.

Valentina Tereshkova, the first woman in space, orbited the Earth 48 times aboard Vostok 6 on June 16, 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on October 15, 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Spaceboat 5) spacecraft.

First planetary explorations

The first artificial object to reach another celestial body was Luna 2 in 1959.^[6] The first automatic landing on another celestial body was performed by Luna 9^[7] in 1966. Luna 10 became the first artificial satellite of another celestial body^[8].

The first manned landing on another celestial body was performed by Apollo 11 in its lunar landing on July 20, 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). Flybys for the other planets were first achieved in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, and 1989 for Neptune by Voyager 2.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus which returned data to earth for 23 minutes. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later much longer duration surface missions were achieved, including over 6 years of Mars surface operation by Viking 1 from 1975 to 1982 and over 2 hours of transmission from the surface of Venus by Venera 13 in 1982 (the longest ever Soviet planetary surface mission).

Key people in early space exploration

The dream of stepping into the outer reaches of the Earth's atmosphere was driven by rocket technology. The German V2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when USSR launched the first man into space, the U.S. declared itself to be in a "Space Race" with Russia.

• Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tilling laid the groundwork of rocketry in the early years of the 20th century.
• Wernher von Braun was the lead rocket engineer for Nazi Germany's World War II V-2 rocket project. In the last days of the war he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the USA to work on U.S. rocket development. He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA's Marshall Space Flight Center which developed the Saturn V moon rocket.
• Initially the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuz—which remain in service to this day. Korolev was the mastermind behind the first satellite, first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Russian space program.
• Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov's death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186 and Cosmos 188.^[9][10]

Robert Gilruth

Other key people included:

• Valentin Glushko held the role of Chief Engine Designer for USSR. Glushko designed many of the engines used on the early Soviet rockets, but was constantly at odds with Korolyov.
• Vasily Mishin was Chief Designer working under Sergey Korolyov and one of first Soviets to inspect the captured German V2 design. Following the death of Sergei Korolev, Mishin was held responsible for the Soviet failure to be first country to place a man on the moon.
• Bob Gilruth was the NASA head of the Space Task Force and director of 25 manned space flights. Gilruth was the person who suggested to John F. Kennedy that the Americans take the bold step of reaching the Moon in an attempt to reclaim space superiority from the Soviets.
• Christopher C. Kraft, Jr. was NASA's first flight director, who oversaw development of Mission Control and associated technologies and procedures.
• Maxime Faget was the designer of the Mercury capsule; he played a key role in designing the Gemini and Apollo spacecraft, and contributed to the design of the Space Shuttle.

Future of space exploration

The European Space Agency's Columbus Module at the International Space Station, launched into space on the U.S. Space Shuttle mission STS-122 in 2008

In the 2000s, several plans for space exploration have been announced; both government entities and the private sector have space exploration objectives.

Targets of exploration

Astrobiology

Main article: Astrobiology

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.^[11] It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: έξω, exo, "outside").^[12][13][14] The term "Xenobiology" has been used as well, but this is technically incorrect because its terminology means "biology of the foreigners".^[15] Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on earth.^[16]

Image of the Sun from 7 June 1992 showing some sunspots

The Sun

While the Sun will probably not be physically explored in the close future, one of the reasons for going into space includes knowing more about the Sun. Once above the atmosphere in particular and the Earth's magnetic field, this gives access to the Solar wind and infrared and ultraviolet radiations that cannot reach the surface of the Earth. The Sun generates most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes.

MESSENGER image of Mercury A MESSENGER image from 18,000 km showing a region about 500 km across

Mercury

Main article: Exploration of Mercury

Mercury remains the least explored of the inner planets. As of January 2008, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury. MESSENGER made a fly-by of Mercury on 14 January 2008, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b). A third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10's flybys.

Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Mariner 10 image of Venus Surface image of Venus taken by Venera 13

Venus

Main article: Observations and explorations of Venus

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the solar system, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the solar system. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970 Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiter Venera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

The "marble" Earth picture taken by Apollo 17 First television image of Earth from space

Earth

Main article: Earth observation satellite

Space exploration has been used as a tool to understand the Earth as a celestial object in its own right. Orbital missions can provide data for the Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the Van Allen belts was unknown until their discovery by the United States' first artificial satellite, Explorer 1. These belts contain radiation trapped by the Earth's magnetic fields, which currently renders construction of habitable space stations above 1000 km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore the Earth from a space based perspective. These satellites have significantly contributed to the understanding of a variety of earth based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth's atmosphere, and satellites have allowed for the discovery of archeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon as seen from the Earth Luc Viatour (Belgium) Apollo 16 astronaut John Young

Earth's Moon

Main article: Exploration of the Moon

Earth's Moon was the first celestial object (apart from the Earth itself) to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon's surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. landers. The Soviet unmanned missions culminated in the Lunokhod program in the early '70s which included the first unmanned rovers and also successfully returned lunar soil samples to the Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to the Earth. Unmanned exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian Moon Impact Probe.

Manned exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969 the Apollo 11 mission marked the first time humans set foot upon another world. Manned exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the last time humans would visit the Moon in any form and no human exploration mission is planned to reach the Moon any time in the near future.

Mars as seen by the HST Part of a panorama taken by the Spirit rover in 2004

Mars

Main article: Exploration of Mars

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, and Japan. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and large number of variables involved in an interplanetary journey, and has led researchers to jokingly speak of The Great Galactic Ghoul^[17] which subsists on a diet of Mars probes. This phenomenon is also informally known as the Mars Curse.^[18]

Photos

Main article: Exploration of Phobos

The Russian space mission Phobos-Grunt, Scheduled to launch in 2011^[19], will begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a "trans-shipment point" for spaceships travelling to Mars.^[20]

Voyager 1 image of Jupiter Image of Io taken by the Galileo spacecraft

Jupiter

Main article: Exploration of Jupiter

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been "flybys", in which detailed observations are taken without the probe landing or entering orbit; the Galileo spacecraft is the only one to have orbited the planet. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2 km/s,^[21] which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit.^[22] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.^[21]

Jupiter has over 60 known moons, many of which have relatively little known about them.

A picture of Saturn taken by Voyager 2. Huygens image from the surface of Titan

Saturn

Main article: Exploration of Saturn

Saturn has been explored only through unmanned spacecraft launched by NASA, including one mission (Cassini–Huygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft which entered orbit in 2004 and is expected to continue its mission well into 2010.

Saturn has at least 60 satellites, although the exact number is debatable since Saturn's rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan. Titan holds the distinction of being the only moon in the solar system with an atmosphere denser and thicker than that of the Earth. As a result of the deployment from the Cassini spacecraft of the Huygens probe and its successful landing on Titan, Titan also holds the distinction of being the only moon (apart from Earth's own Moon) to be successfully explored with a lander.

Uranus from Voyager 2 Voyager 2 image showing the tortured surface of Miranda

Uranus

Main article: Exploration of Uranus

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given its axial tilt of 97.77°, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on January 24, 1986. Voyager 2 studied the planet's unique atmosphere and magnetosphere. Voyager 2 also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet's unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the moons of Uranus, including evidence that Miranda had been unusually geologically active.

Picture of Neptune taken by Voyager 2 Triton as imaged by Voyager 2

Neptune

Main article: Exploration of Neptune

The exploration of Neptune began with the August 25, 1989 Voyager 2 flyby, the sole visit to the system as of 2009. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2's visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, Voyager 2 found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivaled in size only by Jupiter's Great Spot. Neptune also proved to have the fastest winds of any planet in the solar system, measured as high as 2,100 km/h.^[23] Voyager 2 also examined Neptune's ring and moon system. It discovered four complete rings and additional partial ring "arcs" around Neptune. In addition to examining Neptune's three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the second largest moon in the system. Data from Voyager further reinforced the view that Neptune's largest moon, Triton, is a captured Kuiper belt object.^[24]

Map of Pluto based on Charon eclipses, approximately true color and among the highest resolutions possible with current technology

Dwarf planets

Pluto

Main article: Exploration of Pluto

The dwarf planet Pluto (considered a planet until the IAU redefinition of "planet" in October 2006^[25]) presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn's moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.^[26]

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy bodies of intermediate size, in mass between the remaining eight planets and the small rocky objects historically termed asteroids (and also the first member of the important subclass, defined by orbit and known as "Plutinos"). After an intense political battle, a mission to Pluto dubbed New Horizons was granted funding from the US government in 2003.^[27] New Horizons was launched successfully on January 19, 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto will be on July 14, 2015; scientific observations of Pluto will begin five months prior to closest approach and will continue for at least a month after the encounter.

Eris and Dysnomia by Hubble

Eris

Main article: Eris (dwarf planet)

Eris is the largest known dwarf planet in the Solar System and the ninth-largest body known to orbit the Sun directly, it was discovered in January 2005 by a Palomar Observatory. Eris is approximately 2,500 kilometres in diameter and 27% more massive than Pluto. It has one moon named Dysnomia. The current distance from the Sun is 96.7 AU, roughly three times that of Pluto. With the exception of some comets the pair are the most distant known natural objects in the Solar System.

Ceres as imaged by Hubble

Ceres

Main article: Ceres (dwarf planet)

Ceres is relatively ill explored at present, but in 2015 Nasa's Dawn space probe is expected to arrive at and enter into orbit around the dwarf planet.

951 Gaspra

Asteroids

Main article: Exploration of the asteroids

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo's planned trajectory to Jupiter that they could be visited at acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, are targets of NASA's Dawn mission, launched in 2007 September.

Rationales

Main article: Space advocacy Astronaut Buzz Aldrin, a Christian, had a personal Communion service when he first arrived on the surface of the Moon.

The research that is conducted by national space exploration agencies, such as NASA and the RKA, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (from things such as spin-offs), generating many times the revenue of the cost of the program.^[28]

Another claim is that space exploration is a necessity to mankind and that staying on our home planet will lead us to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, renowned British theoretical physicist, said that "I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars."^[29]

NASA has produced a series of Public Service Announcement videos supporting the concept of space exploration.^[30]

Overall, the public remains largely supportive of both manned and unmanned space exploration. According to an Associated Press Poll conducted in July 2003, 71% of U.S. citizens agreed with the statement that the space program is "a good investment", compared to 21% who did not.^[31]

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight.^[32] He argued that humanity's choice is essentially between expansion off the Earth into space, versus cultural (and eventually biological) stagnation and death.

Opposition

Critics such as the late physicist and Nobel prize winner Richard Feynman have contended that human space travel (as distinguished from space exploration in general, such as robotic missions) has never achieved any major scientific breakthroughs.^[33]

Related topics

Spaceflight

Main article: Spaceflight

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft—both when unpropelled and when under propulsion—is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites

Main article: Satellite

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Militarization of space

Main article: Militarisation of space

Militarisation of space took place since the 1960s, and is now evolving into weaponisation of space with actual placement of weapons by space-faring nations for decisive military advantage.

While military activities have certainly taken place in space and space is an operating location for many military spacecraft (such as imaging & communications satellites) or a temporary transit medium for weapons (such as ballistic missiles), permanent placement of large-scale operational weapons in space has never been conducted.

Space colonization

Main article: Space colonization

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of in-situ resource utilization.

To date, the longest human occupation of space was the space station Mir, which was continuously inhabited for almost ten years, including Valeri Polyakov's record single spaceflight of almost 438 days. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonization of space focus on a return to the Moon as a "stepping stone" to the other planets, especially Mars. At the end of 2006 NASA announced they were planning to build a permanent Moon base with continual presence by 2024.^[34]

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See also

Spaceflight portal

Wikimedia Commons has media related to: Space exploration

Main article: Outline of space exploration

Robotic space exploration programs

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References

1. ^ "How Space is Explored". NASA. http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html.
2. ^ Roach, John (September 19, 2005). "NASA Aims for Moon by 2018, Unveils New Ship". National Geographic. http://news.nationalgeographic.com/news/2005/09/0919_050919_moon_space.html. Retrieved July 14, 2009.
3. ^ Berger, Brian (September 14, 2005). "NASA to Unveil Plans to Send 4 Astronauts to Moon in 2018". Space.com. http://www.space.com/news/050914_nasa_cev_update.html. Retrieved July 14, 2005.
4. ^ Elsworth, Catherine (September 20, 2005). "US plans to be back on the Moon by 2018". The Daily Telegraph (London). http://www.telegraph.co.uk/news/worldnews/northamerica/usa/1498804/US-plans-to-be-back-on-the-moon-by-2018.html. Retrieved July 14, 2009.
5. ^ Russia proposes manned Mars mission by 2015 - 08 July 2002 - New Scientist
6. ^ NASA on Luna 2 mission
7. ^ NASA on Luna 9 mission
8. ^ NASA on Luna 10 mission
9. ^ Bond, Peter (7 April 2003), "Obituary: Lt-Gen Kerim Kerimov", The Independent (London), http://findarticles.com/p/articles/mi_qn4158/is_20030407/ai_n12692130, retrieved 2009-03-11
10. ^ Betty Blair (1995), "Behind Soviet Aeronauts", Azerbaijan International 3 (3).
11. ^ NASA Astrobiology
12. ^ http://www.aleph.se/Trans/Words/x.html
13. ^ World Wide Words: Fears and dreads
14. ^ iTWire - Scientists will look for alien life, but Where and How?
15. ^ Astrobiology
16. ^ Launching the Alien Debates :: Astrobiology Magazine - earth science - evolution distribution Origin of life universe - life beyond :: Astrobiology is study of earth science evolution distribution Origin of life in universe terrestrial
17. ^ Dinerman, Taylor (September 27, 2004). "Is the Great Galactic Ghoul losing his appetite?". The space review. http://www.thespacereview.com/article/232/1. Retrieved 2007-03-27.
18. ^ Knight, Matthew. "Beating the curse of Mars". Science & Space. http://www.cnn.com/2006/TECH/science/12/23/mwonders.mars/index.html. Retrieved 2007-03-27.
19. ^ http://www.marsdaily.com/reports/Russia_delays_Mars_probe_launch_until_2012_report_999.html
20. ^ http://ru.youtube.com/watch?v=W0cUvK0Dgy8
21. ^ ^{a b} Wong, Al (May 28, 1998). "Galileo FAQ - Navigation". NASA. http://www2.jpl.nasa.gov/galileo/faqnav.html. Retrieved 2006-11-28.
22. ^ Hirata, Chris. "Delta-V in the Solar System". California Institute of Technology. http://www.pma.caltech.edu/~chirata/deltav.html. Retrieved 2006-11-28.
23. ^ Suomi, V. E.; Limaye, S. S.; Johnson, D. R. (1991). "High winds of Neptune - A possible mechanism". Science 251: 929–932. doi:10.1126/science.251.4996.929+. http://adsabs.harvard.edu/abs/1991Sci...251..929S.
24. ^ Agnor, C. B.; and Hamilton, D. P. (2006). "Neptune's capture of its moon Triton in a binary–planet gravitational encounter". Nature 441: 192. doi:10.1038/nature04792. http://www.nature.com/nature/journal/v441/n7090/abs/nature04792.html. Retrieved 2006-05-10.
25. ^ IAU 2006 General Assembly: Result of the IAU Resolution votes. International Astronomical Union (2006)Staff (2006). "IAU 2006 General Assembly: Result of the IAU resolution votes". IAU. http://www.iau.org/iau0603.414.0.html. Retrieved 2007-05-11. .
26. ^ "Voyager Frequently Asked Questions". Jet Propulsion Laboratory. January 14, 2003. http://voyager.jpl.nasa.gov/faq.html. Retrieved 2006-09-08.
27. ^ Robert Roy Britt (2003). "Pluto Mission a Go! Initial Funding Secured". space.com. http://www.space.com/scienceastronomy/pluto_horizons_030225.html. Retrieved 2007-04-13.
28. ^ [1]
29. ^ Highfield, Roger (October 15, 2001). "Colonies in space may be only hope, says Hawking". London: Telegraph.co.uk. http://www.telegraph.co.uk/news/main.jhtml?xml=/news/2001/10/16/nhawk16.xml. Retrieved 2007-08-05.
30. ^ "NASA "Reach" Public Service Announcement for Space Exploration". NASA. http://www.youtube.com/watch?v=EewrC22ysus.
31. ^ "Origin of Human Life – USA Today/Gallup Poll". Pollingreport.com. June 1–3, 2007. http://www.pollingreport.com/science.htm. Retrieved 2007-08-05.
32. ^ Arthur C. Clarke, Interplanetary Flight -- An Introduction to Astronautics, Harper & Brothers, New York, 1950,Chapter 10
33. ^ [Feynman, Richard P., What Do You Care What Other People Think?, 1988, W W Norton, ISBN 0-393-02659-0, 2001 paperback: ISBN 0-393-32092-8]
34. ^ NASA (December 4, 2006). "GLOBAL EXPLORATION STRATEGY AND LUNAR ARCHITECTURE" (PDF). Press release. http://www.nasa.gov/pdf/164021main_lunar_architecture.pdf. Retrieved 2007-08-05.

External links

• Space related news
• Nasa's website on human space travel
• "America's Space Program: Exploring a New Frontier", a National Park Service Teaching with Historic Places (TwHP) lesson plan
• The Soviet-Russian Spaceflight's History Photoarchive
• The 21 Greatest Space Photos Ever - slideshow by Life Magazine

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