View source for Astronomy:Space exploration

{{Short description|Exploration of space, planets, and moons}}
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[[File:AS11-40-5964 (21037459754).jpg|thumb|Buzz Aldrin taking a core sample of the Moon during the Apollo 11 mission]]
[[File:PIA16239 High-Resolution Self-Portrait by Curiosity Rover Arm Camera square.jpg|thumb|Self-portrait of [[Engineering:Curiosity (rover)|''Curiosity'' rover]] on Mars's surface]]

'''Space exploration''' is the use of [[Astronomy:Astronomy|astronomy]] and [[Engineering:Space technology|space technology]] to explore [[Astronomy:Outer space|outer space]].<ref>
{{cite web | url = http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html | title = How Space is Explored | publisher = NASA | url-status = dead | archive-url = https://web.archive.org/web/20090702153058/http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html | archive-date = 2009-07-02 }}</ref> While the exploration of space is currently carried out mainly by [[Astronomy:Astronomer|astronomer]]s with [[Astronomy:Telescope|telescope]]s, its physical exploration is conducted both by [[Engineering:Robotic spacecraft|uncrewed robotic space probes]] and [[Astronomy:Human spaceflight|human spaceflight]]. Space exploration, like its classical form [[Astronomy:Astronomy|astronomy]], is one of the main sources for [[Astronomy:Space science|space science]].

While the observation of objects in space, known as [[Astronomy:Astronomy|astronomy]], predates reliable [[History:Recorded history|recorded history]], it was the development of large and relatively efficient [[Engineering:Rocket|rocket]]s during the mid-twentieth century that allowed physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, national prestige, uniting different nations, ensuring the future survival of humanity, and developing military and strategic advantages against other countries.<ref name="NYT-20150828">{{cite news |last=Roston |first=Michael |title=NASA's Next Horizon in Space |url=https://www.nytimes.com/interactive/2015/08/25/science/space/nasa-next-mission.html |date=28 August 2015 |work={{wipe|The New York Times}}|access-date=28 August 2015 }}</ref>

The early era of space exploration was driven by a "[[Astronomy:Space Race|Space Race]]" between the [[Place:Soviet Union|Soviet Union]] and the {{wipe|United States}}. A driving force of the start of space exploration was during the Cold War. After the ability to create nuclear weapons, the narrative of defense/offense left land and the power to control the air became the focus. Both the Soviet and the U.S. were fighting to prove their superiority in technology through exploring the unknown: space. In fact, the reason NASA was made was due to the response of Sputnik I.<ref>{{Cite web |title=NASA Created |url=https://www.history.com/this-day-in-history/nasa-created |access-date=2023-04-27 |website=HISTORY |language=en}}</ref> The launch of the first human-made object to orbit [[Astronomy:Earth|Earth]], the Soviet Union's [[Engineering:Sputnik 1|Sputnik 1]], on 4 October 1957, and the first [[Astronomy:Moon landing|Moon landing]] by the American [[Engineering:Apollo 11|Apollo 11]] mission on 20 July 1969 are often taken as landmarks for this initial period. The Soviet space program achieved many of the first milestones, including the first living being in orbit in 1957, the first [[Astronomy:Human spaceflight|human spaceflight]] ([[Biography:Yuri Gagarin|Yuri Gagarin]] aboard ''[[Astronomy:Vostok 1|Vostok 1]]'') in 1961, the first spacewalk (by Alexei Leonov) on 18 March 1965, the [[Astronomy:Luna 9|first automatic landing]] on another celestial body in 1966, and the launch of the first space station (''[[Engineering:Salyut 1|Salyut 1]]'') in 1971. 
After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as the [[Engineering:Space Shuttle program|Space Shuttle program]], and from competition to cooperation as with the [[Astronomy:International Space Station|International Space Station]] (ISS).

With the substantial completion of the ISS<ref name="space-11078">{{cite news |url=http://www.space.com/11078-space-station-complete.html |title=After 13 Years, International Space Station Has All Its NASA Rooms |first=Denise |last=Chow |work=Space.com |date=9 March 2011 }}</ref> following [[Engineering:STS-133|STS-133]] in March 2011, plans for space exploration by the U.S. remain in flux. [[Astronomy:Constellation program|Constellation]], a Bush administration program for a return to the Moon by 2020<ref name="nasa-163092">{{cite web |url=http://www.nasa.gov/pdf/163092main_constellation_program_overview.pdf |title=Constellation Program Overview |last=Connolly |first=John F. |date=October 2006 |publisher=Constellation Program Office |access-date=6 July 2009 |archive-url=https://web.archive.org/web/20070710060512/http://www.nasa.gov/pdf/163092main_constellation_program_overview.pdf |archive-date=10 July 2007 }}</ref> was judged inadequately funded and unrealistic by an expert review panel reporting in 2009.<ref name="sm-200910">{{cite web|url=http://news.sciencemag.org/scienceinsider/2009/10/no-nasa-augusti.html |title=No to NASA: Augustine Commission Wants to More Boldly Go |publisher=Science |first=Andrew |last=Lawler |date=22 October 2009 |url-status=dead |archive-url=https://web.archive.org/web/20130513130114/http://news.sciencemag.org/scienceinsider/2009/10/no-nasa-augusti.html |archive-date=13 May 2013 }}</ref> 
The Obama administration proposed a revision of Constellation in 2010 to focus on the development of the capability for crewed missions beyond [[Astronomy:Low Earth orbit|low Earth orbit]] (LEO), envisioning extending the operation of the [[Astronomy:International Space Station|ISS]] beyond 2020, transferring the development of [[Engineering:Launch vehicle|launch vehicle]]s for human crews from [[Organization:NASA|NASA]] to the private sector, and developing technology to enable missions to beyond LEO, such as [[Astronomy:Lagrange point|Earth–Moon L1]], the Moon, [[Astronomy:Lagrange point|Earth–Sun L2]], near-Earth asteroids, and [[Astronomy:Phobos (moon)|Phobos]] or Mars orbit.<ref name="obama">{{cite web |url=http://www.nasa.gov/about/obamaspeechfeature_prt.htm |work=Address at KSC |date=15 April 2010 |title=President Outlines Exploration Goals, Promise }}</ref>

In the 2000s, {{wipe|China}} initiated a successful crewed spaceflight program while {{wipe|India}} launched [[Astronomy:Chandrayaan-1|Chandraayan 1]], while the [[Social:European Union|European Union]] and {{wipe|Japan}} have also planned future crewed space missions. China, Russia, and Japan have advocated crewed missions to the Moon during the 21st century, while the European Union has advocated [[Astronomy:Aurora programme|crewed missions to both the Moon and Mars]] during the 20th and 21st century.

==History of exploration{{anchor|History|History_of_exploration_in_the_20th_century}}==
[[File:Fusée V2.jpg|thumb|V-2 Rocket in the Peenemünde Museum]]

===First telescopes===
The first [[Astronomy:Telescope|telescope]] is said to have been invented in 1608 in the Netherlands by an eyeglass maker named [[Biography:Hans Lippershey|Hans Lippershey]], but their first recorded use in astronomy was by [[Biography:Galileo Galilei|Galileo Galilei]] in 1609.<ref>{{cite book |author=King, C. C.|date=2003|title=The History of the Telescope|publisher=Dover Publications|pages=30–32|isbn=978-0-486-43265-6}}</ref> In 1668 [[Biography:Isaac Newton|Isaac Newton]] built [[Astronomy:Newton's reflector|his own]] [[Astronomy:Reflecting telescope|reflecting telescope]], the first fully functional telescope of this kind, and a landmark for future developments due to its superior features over the previous [[Astronomy:Refracting telescope#Galilean telescope|Galilean telescope]].<ref name="books.google.com">{{cite book|author=A. Rupert Hall|title=Isaac Newton: Adventurer in Thought|url=https://archive.org/details/isaacnewtonadven0000hall|url-access=registration|year=1996|publisher=Cambridge University Press|isbn=978-0-521-56669-8|page=[https://archive.org/details/isaacnewtonadven0000hall/page/67 67]}}</ref>

A string of discoveries in the Solar System (and beyond) followed, then and in the next centuries: the [[Astronomy:Lunar craters|mountains of the Moon]], the [[Astronomy:Phases of Venus|phases of Venus]], the main satellites of Jupiter and Saturn, the rings of Saturn, many [[Astronomy:Comet|comet]]s, the [[Astronomy:Asteroid|asteroid]]s, the new planets [[Astronomy:Uranus|Uranus]] and [[Astronomy:Neptune|Neptune]], and many more [[Astronomy:List of natural satellites|satellites]].

The [[Astronomy:Orbiting Astronomical Observatory 2|Orbiting Astronomical Observatory 2]] was the first [[Astronomy:Space telescope|space telescope]] launched 1968,<ref name=joseph>{{cite book|first=Joseph A.|last=Angelo|title=Spacecraft for Astronomy |url= https://books.google.com/books?id=y8BMepjeciEC&pg=PA20|year=2014|publisher=Infobase Publishing|isbn=978-1-4381-0896-4|page=20}}</ref> but the launching of [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]] in 1990<ref>{{cite web |url=http://science.ksc.nasa.gov/shuttle/missions/sts-31/mission-sts-31.html |title=STS-31 |publisher=NASA |access-date=April 26, 2008 |archive-date= August 15, 2011 |archive-url= https://web.archive.org/web/20110815191242/http://science.ksc.nasa.gov/shuttle/missions/sts-31/mission-sts-31.html |url-status=live }}</ref> set a milestone. As of 1 December 2022, there were 5,284 confirmed [[Astronomy:Lists of exoplanets|exoplanets]] discovered. The [[Astronomy:Milky Way|Milky Way]] is estimated to contain 100–400 billion [[Astronomy:Star|star]]s<ref>{{cite web |url= http://asd.gsfc.nasa.gov/blueshift/index.php/2015/07/22/how-many-stars-in-the-milky-way/ |title=How Many Stars in the Milky Way? |work=NASA Blueshift |url-status=live |archive-url= https://web.archive.org/web/20160125140109/http://asd.gsfc.nasa.gov/blueshift/index.php/2015/07/22/how-many-stars-in-the-milky-way/ |archive-date=25 January 2016 }}</ref> and more than 100 billion planets.<ref name="Space-20130102">{{cite news |author=|title=100 Billion Alien Planets Fill Our Milky Way Galaxy: Study |url=http://www.space.com/19103-milky-way-100-billion-planets.html |date=2 January 2013 |work=Space.com |access-date= |archive-url=https://web.archive.org/web/20130103060601/http://www.space.com/19103-milky-way-100-billion-planets.html |archive-date=3 January 2013 |url-status=live}}</ref> There are at least 2 trillion [[Astronomy:Galaxy|galaxies]] in the [[Astronomy:Observable universe|observable universe]].<ref name="Conselice">{{cite journal |title= The Evolution of Galaxy Number Density at ''z'' < 8 and Its Implications |first=Christopher J. |last=Conselice |display-authors=0 |journal=The Astrophysical Journal |volume= 830 |issue=2 |year=2016 |arxiv=1607.03909v2 |bibcode= 2016ApJ...830...83C |doi=10.3847/0004-637X/830/2/83 |page=83|s2cid=17424588 |doi-access=free }}</ref><ref name="NYT-20161017">{{cite news |last=Fountain |first=Henry |title=Two Trillion Galaxies, at the Very Least |url=https://www.nytimes.com/2016/10/18/science/two-trillion-galaxies-at-the-very-least.html |date=17 October 2016 |work={{wipe|The New York Times}}|access-date=17 October 2016 }}</ref> [[Astronomy:HD1|HD1]] is the [[Astronomy:List of the most distant astronomical objects|most distant]] known object from Earth, reported as 33.4 billion [[Astronomy:Light-year|light-year]]s away.<ref name="ALMA-20220407">{{cite news |last1=Lira |first1=Nicolás |last2=Iono |first2=Daisuke |last3=Oliver |first3=Amy c. |last4=Ferreira |first4= Bárbara |title=Astronomers Detect Most Distant Galaxy Candidate Yet |url=https://www.almaobservatory.org/en/press-releases/astronomers-detect-most-distant-galaxy-candidate-yet/ |date= 7 April 2022 |work=[[Astronomy:Atacama Large Millimeter Array|Atacama Large Millimeter Array]] |accessdate=8 April 2022 |archive-date=17 July 2022 |archive-url=https://web.archive.org/web/20220717040741/https://www.almaobservatory.org/en/press-releases/astronomers-detect-most-distant-galaxy-candidate-yet/ |url-status=dead }}</ref><ref name="ARX-20220212">{{cite journal |author=Harikane, Yuichi |display-authors=et al. |title=A Search for H-Dropout Lyman Break Galaxies at z ∼ 12–16 |journal=The Astrophysical Journal |arxiv=2112.09141 |date=2 February 2022 |volume=929 |issue= 1 |page=1 |doi=10.3847/1538-4357/ac53a9 |bibcode=2022ApJ...929....1H |s2cid=246823511 |doi-access=free }}</ref><ref name="NS-20220407">{{cite news |last=Crane |first=Leah |title= Astronomers have found what may be the most distant galaxy ever seen – A galaxy called HD1 appears to be about 33.4 billion light years away, making it the most distant object ever seen – and its extreme brightness is puzzling researchers |url=https://www.newscientist.com/article/2315330-astronomers-have-found-what-may-be-the-most-distant-galaxy-ever-seen/ |date=7 April 2022 |work=New Scientist |accessdate=8 April 2022 }}</ref><ref name="MN-20220407">{{cite journal |author=Pacucci, Fabio |display-authors=et al. |title=Are the newly-discovered z ∼ 13 drop-out sources starburst galaxies or quasars? |url=https://academic.oup.com/mnrasl/advance-article-abstract/doi/10.1093/mnrasl/slac035/6564647 |date=7 April 2022 |journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] |volume=514 |pages=L6–L10 |doi=10.1093/mnrasl/slac035 |accessdate=7 April 2022 |arxiv=2201.00823 }}</ref><ref name="AST-20220407">{{cite news |last=Buongiorno |first=Caitlyn |title=Astronomers discover the most distant galaxy yet - Unusually bright in ultraviolet light, HD1 may also set another cosmic record. |url=https://astronomy.com/news/2022/04/researchers-discover-the-most-distant-galaxy-yet |date=7 April 2022 |work=[[Astronomy:Astronomy (magazine)|Astronomy]] |accessdate=7 April 2022 }}</ref><ref name="INV-20220407">{{cite news |last=Wenz |first=John |title=Behold! Astronomers May Have Discovered The Most Distant Galaxy Ever – HD1 could be from just 300 million years after the Big Bang. |url=https://www.inverse.com/science/most-distant-galaxy-discovery |date=7 April 2022 |work=Inverse |accessdate=7 April 2022 }}</ref>

===First outer space flights===
[[File:Vostok spacecraft.jpg|thumb|Model of Vostok spacecraft]]
[[File:Apollo CSM lunar orbit.jpg|thumb|Apollo CSM in lunar orbit]]

[[Engineering:MW 18014|MW 18014]] was a German [[Engineering:V-2 rocket|V-2 rocket]] test launch that took place on 20 June 1944, at the Peenemünde Army Research Center in Peenemünde. It was the first man-made object to reach [[Astronomy:Outer space|outer space]], attaining an apogee of 176 kilometers,<ref name="psv">{{cite journal |author=M.P. Milazzo |author2=L. Kestay |author3=C. Dundas |author4=U.S. Geological Survey |title=The Challenge for 2050: Cohesive Analysis of More Than One Hundred Years of Planetary Data |journal=Planetary Science Vision 2050 Workshop |volume=1989 |pages=8070 |url=https://www.hou.usra.edu/meetings/V2050/pdf/8070.pdf |publisher=Planetary Science Division, NASA |accessdate=2019-06-07|bibcode=2017LPICo1989.8070M |year=2017 }}</ref> which is well above the [[Earth:Kármán line|Kármán line]].<ref name="Karman line">{{cite web | url=http://www.universetoday.com/25410/how-far-is-space/ | title=How high is space? | website=Universe Today | last=Williams | first=Matt | date=2016-09-16 | accessdate=2017-05-14 | url-status=live | archiveurl=https://web.archive.org/web/20170602105939/https://www.universetoday.com/25410/how-far-is-space/ | archivedate=2017-06-02 }}</ref> It was a vertical test launch. Although the rocket reached space, it did not reach [[Astronomy:Orbital speed|orbital velocity]], and therefore returned to Earth in an impact, becoming the first [[Engineering:Sub-orbital spaceflight|sub-orbital spaceflight]].<ref>{{cite web |title=V-2 rocket (MW 18014) became the first human-made object in space on June 20, 1944 |url=https://ourplnt.com/v-2-rocket-mw-18014-first-human-made-object-in-space/ |website=Our Planet |date=20 June 2022 |access-date=11 July 2022}}</ref>

===First object in orbit===
The first successful orbital launch was of the [[Place:Soviet Union|Soviet]] uncrewed ''[[Engineering:Sputnik 1|Sputnik 1]]'' ("Satellite 1") mission on 4 October 1957. The satellite weighed about {{convert|83|kg|lb|abbr=on}}, and is believed to have orbited Earth at a height of about {{convert|250|km|mi|abbr=on}}. It had two radio transmitters (20 and 40&nbsp;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 [[Astronomy:Meteoroid|meteoroid]]. ''Sputnik 1'' was launched by an [[Engineering:R-7 Semyorka|R-7]] rocket. It burned up upon re-entry on 3 January 1958.

===First human outer space flight===
The first successful human spaceflight was ''[[Astronomy:Vostok 1|Vostok 1]]'' ("East 1"), carrying the 27-year-old Russian [[Biography:Cosmonaut|cosmonaut]], [[Biography:Yuri Gagarin|Yuri Gagarin]], on 12 April 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 [[Astronomy:Soviet space program|Soviet space program]] and it opened an entirely new era in space exploration: [[Astronomy:Human spaceflight|human spaceflight]].

=== First astronomical body space explorations ===
The first artificial object to reach another celestial body was [[Engineering:Luna 2|Luna 2]] reaching the [[Astronomy:Moon|Moon]] in 1959.<ref name="jpl-luna2">{{cite web|url=http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&MCode=Luna_02 |title=NASA on Luna 2 mission |publisher=Sse.jpl.nasa.gov |access-date=24 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120331155310/http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&MCode=Luna_02 |archive-date=31 March 2012 }}</ref> The first [[Engineering:Soft landing (aeronautics)|soft landing]] on another celestial body was performed by [[Astronomy:Luna 9|Luna 9]] landing on the Moon on 3 February 1966.<ref name="jpl.luna9">{{cite web|url=http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&MCode=Luna_09 |title=NASA on Luna 9 mission |publisher=Sse.jpl.nasa.gov |access-date=24 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120331155324/http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&MCode=Luna_09 |archive-date=31 March 2012 }}</ref> [[Engineering:Luna 10|Luna 10]] became the first artificial satellite of the Moon, entering in a lunar orbit on 3 April 1966.<ref name="jpl-luna10">{{cite web|url=http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&MCode=Luna_10 |title=NASA on Luna 10 mission |publisher=Sse.jpl.nasa.gov |access-date=24 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120218232128/http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Target&Target=Moon&MCode=Luna_10 |archive-date=18 February 2012 }}</ref>

The first crewed landing on another celestial body was performed by [[Engineering:Apollo 11|Apollo 11]] on 20 July 1969, landing on the Moon. There have been a total of six spacecraft with humans [[Astronomy:Moon landing|landing on the Moon]] starting from 1969 to the last human landing in 1972.

The first interplanetary [[Engineering:Flyby (spaceflight)|flyby]] was the 1961 [[Astronomy:Venera 1|Venera 1]] flyby of [[Astronomy:Venus|Venus]], though the 1962 [[Astronomy:Mariner 2|Mariner 2]] was the first flyby of [[Astronomy:Venus|Venus]] to return data (closest approach 34,773 kilometers). [[Astronomy:Pioneer 6, 7, 8, and 9|Pioneer 6]] was the first satellite to orbit the [[Astronomy:Sun|Sun]], launched on 16 December 1965. The other planets were first flown by in 1965 for [[Astronomy:Mars|Mars]] by [[Astronomy:Mariner 4|Mariner 4]], 1973 for [[Astronomy:Jupiter|Jupiter]] by ''[[Astronomy:Pioneer 10|Pioneer 10]]'', 1974 for [[Astronomy:Mercury (planet)|Mercury]] by [[Astronomy:Mariner 10|Mariner 10]], 1979 for [[Astronomy:Saturn|Saturn]] by ''[[Astronomy:Pioneer 11|Pioneer 11]]'', 1986 for [[Astronomy:Uranus|Uranus]] by ''[[Astronomy:Voyager 2|Voyager 2]]'', 1989 for [[Astronomy:Neptune|Neptune]] by ''[[Astronomy:Voyager 2|Voyager 2]]''. In 2015, the [[Astronomy:Dwarf planet|dwarf planet]]s [[Astronomy:Ceres (dwarf planet)|Ceres]] and [[Astronomy:Pluto|Pluto]] were orbited by ''[[Engineering:Dawn (spacecraft)|Dawn]]'' and passed by ''[[Astronomy:New Horizons|New Horizons]]'', respectively. This accounts for flybys of each of the eight planets in the [[Astronomy:Solar System|Solar System]], the [[Astronomy:Sun|Sun]], the [[Astronomy:Moon|Moon]], and [[Astronomy:Ceres (dwarf planet)|Ceres]] and [[Astronomy:Pluto|Pluto]] (two of the five [[Astronomy:Dwarf planet#Recognized|recognized dwarf planets]]).

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of [[Astronomy:Venera 7|Venera 7]], which returned data to Earth for 23 minutes from [[Astronomy:Venus|Venus]]. In 1975 the [[Astronomy:Venera 9|Venera 9]] was the first to return images from the surface of another planet, returning images from Venus. In 1971 the [[Astronomy:Mars 3|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 six years of Mars surface operation by [[Astronomy:Viking 1|Viking 1]] from 1975 to 1982 and over two hours of transmission from the surface of Venus by [[Astronomy:Venera 13|Venera 13]] in 1982, the longest ever Soviet planetary surface mission. Venus and Mars are the two planets outside of Earth on which humans have conducted surface missions with uncrewed [[Engineering:Robotic spacecraft|robotic spacecraft]].

=== First space station ===
[[Engineering:Salyut 1|Salyut 1]] was the first space station of any kind, launched into [[Astronomy:Low Earth orbit|low Earth orbit]] by the [[Place:Soviet Union|Soviet Union]] on 19 April 1971. The [[Astronomy:International Space Station|International Space Station]] is currently the largest and oldest of the 2 current fully functional space stations, inhabited continuously since the year 2000. The other, Tiangong space station built by China, is now fully crewed and operational.

===First interstellar space flight===
''[[Astronomy:Voyager 1|Voyager 1]]'' became the first human-made object to leave the Solar System into [[Astronomy:Outer space#Interstellar space|interstellar space]] on 25 August 2012. The probe passed the heliopause at 121 [[Astronomy:Astronomical unit|AU]] to enter [[Astronomy:Interstellar medium|interstellar space]].<ref>{{cite news |title=Voyager 1 finally crosses into interstellar space |first=William |last=Harwood |work=CBS News |date=12 September 2013 |url=http://www.cbsnews.com/8301-205_162-57602736/voyager-1-finally-crosses-into-interstellar-space/ |access-date=1 February 2019 |archive-date=13 November 2013 |archive-url=https://web.archive.org/web/20131113201639/http://www.cbsnews.com/8301-205_162-57602736/voyager-1-finally-crosses-into-interstellar-space/ |url-status=dead }}</ref>

===Farthest from Earth===
The [[Engineering:Apollo 13|Apollo 13]] flight passed the [[Astronomy:Far side of the Moon|far side of the Moon]] at an altitude of {{convert|254|km|mi nmi|sp=us|abbr=off}} above the lunar surface, and 400,171&nbsp;km (248,655&nbsp;mi) from Earth, marking the [[Astronomy:List of spaceflight records|record]] for the farthest humans have ever traveled from Earth in 1970.

{{As of|2022|11|26}} ''[[Astronomy:Voyager 1|Voyager 1]]'' was at a distance of {{convert|159|AU|e9km e9mi|abbr=unit}} from Earth.<ref name="voyager">{{cite web | url=https://voyager.jpl.nasa.gov/mission/status/ | title=Voyager – Mission Status | work=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] | publisher=[[Organization:National Aeronautics and Space Administration|National Aeronautics and Space Administration]] | access-date=1 January 2019}}</ref> It is the most distant human-made object from Earth.<ref>{{cite web |url=http://www.bbc.co.uk/science/space/solarsystem/space_missions/voyager_1 |title=Voyager 1 |work=BBC Solar System |access-date=4 September 2018 |archive-url=https://web.archive.org/web/20180203195855/http://www.bbc.co.uk/science/space/solarsystem/space_missions/voyager_1 |archive-date=3 February 2018 |url-status=dead |df=mdy-all }}</ref>

==Targets of exploration==
Starting in the mid-20th century probes and then human mission were sent into Earth orbit, and then on to the Moon. Also, probes were sent throughout the known Solar System, and into Solar orbit. Uncrewed spacecraft have been sent into orbit around Saturn, Jupiter, Mars, Venus, and Mercury by the 21st century, and the most distance active spacecraft, ''Voyager 1'' and ''2'' traveled beyond 100 times the Earth-Sun distance. The instruments were enough though that it is thought they have left the Sun's heliosphere, a sort of bubble of particles made in the Galaxy by the Sun's [[Astronomy:Solar wind|solar wind]].

===The Sun===
The [[Astronomy:Sun|Sun]] is a major focus of space exploration. Being above the atmosphere in particular and Earth's magnetic field gives access to the solar wind and infrared and ultraviolet radiations that cannot reach Earth's surface. The Sun generates most [[Astronomy:Space weather|space weather]], which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes. Numerous spacecraft dedicated to observing the Sun, beginning with the [[Astronomy:Apollo Telescope Mount|Apollo Telescope Mount]], have been launched and still others have had solar observation as a secondary objective. [[Astronomy:Parker Solar Probe|Parker Solar Probe]], launched in 2018, will approach the Sun to within 1/9th the orbit of Mercury.

===Mercury===
{{main|Astronomy:Exploration of Mercury}}
[[File:MESSENGER EN0108828359M.png|thumb|A ''MESSENGER'' image from 18,000&nbsp;km showing a region about 500&nbsp;km across (2008)]]
[[Astronomy:Mercury (planet)|Mercury]] remains the least explored of the Terrestrial planets. As of May 2013, the [[Astronomy:Mariner 10|Mariner 10]] and ''[[Astronomy:MESSENGER|MESSENGER]]'' missions have been the only missions that have made close observations of Mercury. ''MESSENGER'' entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b).
A third mission to Mercury, scheduled to arrive in 2025, [[Astronomy:BepiColombo|BepiColombo]] is to include two [[Engineering:Space probe|probes]]. BepiColombo is a joint mission between Japan and the [[Organization:European Space Agency|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 [[Astronomy:Delta-v|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.

===Venus===
{{Main|Astronomy:Observations and explorations of Venus}}
[[Astronomy: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 flyby was the 1961&nbsp;[[Astronomy:Venera 1|Venera 1]], though the 1962&nbsp;[[Astronomy:Mariner 2|Mariner 2]]&nbsp;was the first flyby&nbsp;to successfully return data. 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 [[Astronomy:Gravity assist|gravitational assist]] en route to other celestial bodies. In 1967 [[Astronomy:Venera 4|Venera 4]] became the first probe to enter and directly examine the atmosphere of Venus. In 1970, [[Astronomy:Venera 7|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 [[Astronomy:Venera 9|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 [[Engineering:Radar|radar]] to pierce the obscuring atmosphere.

===Earth===
{{Main|Astronomy:Earth observation satellite}}
[[File:TIROS-1-Earth.png|244x244px|thumb|First television image of Earth from space, taken by [[Engineering:TIROS-1|TIROS-1]] (1960)]]Space exploration has been used as a tool to understand Earth as a celestial object. Orbital missions can provide data for Earth that can be difficult or impossible to obtain from a purely ground-based point of reference.

For example, the existence of the [[Astronomy:Van Allen radiation belt|Van Allen radiation belt]]s was unknown until their discovery by the United States' first artificial satellite, ''[[Astronomy:Explorer 1|Explorer 1]]''. These belts contain radiation trapped by Earth's magnetic fields, which currently renders construction of habitable space stations above 1000&nbsp;km impractical.
Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore Earth from a space-based perspective. These satellites have significantly contributed to the understanding of a variety of Earth-based phenomena. For instance, the [[Earth:Ozone depletion|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.

==== Moon ====
{{Main|Astronomy:Exploration of the Moon}}
[[File:Apollo 16 LM Orion.jpg|thumbnail|[[Engineering:Apollo 16|Apollo 16]] LEM Orion, the Lunar Roving Vehicle and astronaut John Young (1972)]]
The [[Astronomy:Moon|Moon]] was the first celestial body 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 [[Astronomy:Far side of the Moon|far side of the Moon]], never previously visible to humans. The U.S. exploration of the Moon began with the [[Astronomy:Ranger 4|Ranger 4]] impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of [[Engineering:Lander (spacecraft)|landers]] to the Moon which were able to obtain data directly from the Moon's surface; just four months later, ''[[Astronomy:Surveyor 1|Surveyor 1]]'' marked the debut of a successful series of U.S. landers. The Soviet uncrewed missions culminated in the [[Astronomy:Lunokhod programme|Lunokhod program]] in the early 1970s, which included the first uncrewed rovers and also successfully brought lunar soil samples to Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to Earth. Uncrewed exploration of the Moon continues with various nations periodically deploying lunar orbiters, and in 2008 the Indian [[Astronomy:Moon Impact Probe|Moon Impact Probe]] and in 2023 the [[Astronomy:Chandrayaan-3|Chandrayaan-3]] of India became the first spacecraft to land on the lunar south pole.

Crewed exploration of the Moon began in 1968 with the [[Engineering:Apollo 8|Apollo 8]] mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969, the [[Engineering:Apollo 11|Apollo 11]] mission marked the first time humans set foot upon another world. Crewed exploration of the Moon did not continue for long. The [[Engineering:Apollo 17|Apollo 17]] mission in 1972 marked the sixth landing and the most recent human visit. [[Astronomy:Artemis 2|Artemis 2]] is scheduled to complete a crewed flyby of the Moon in 2024. Robotic missions are still pursued vigorously.

===Mars===
{{Main|Exploration of Mars}}[[File:Spirit rover tracks.jpg|thumb|220x220px|Surface of Mars by the [[Astronomy:Mars Exploration Rover|''Spirit'' rover]] (2004)]]
The exploration of [[Astronomy:Mars|Mars]] has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, Japan and India. Dozens of [[Engineering:Robotic spacecraft|robotic spacecraft]], including [[Engineering:Orbiter|orbiter]]s, [[Engineering:Lander (spacecraft)|landers]], and [[Astronomy:Rover (space exploration)|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''<ref name="space-232">{{cite web |last=Dinerman |first=Taylor |url=http://www.thespacereview.com/article/232/1 |title=Is the Great Galactic Ghoul losing his appetite? |work=The space review |date=27 September 2004 |access-date=27 March 2007 }}</ref> which subsists on a diet of Mars probes. This phenomenon is also informally known as the "Mars Curse".<ref name="cnn-20061223">{{cite news |last=Knight |first=Matthew |url=http://www.cnn.com/2006/TECH/science/12/23/mwonders.mars/index.html |title=Beating the curse of Mars |work=Science & Space |access-date=27 March 2007 }}</ref>  In contrast to overall high failure rates in the exploration of Mars, {{wipe|India}} has become the first country to achieve success of its maiden attempt.  India's [[Astronomy:Mars Orbiter Mission|Mars Orbiter Mission]] (MOM)<ref>{{cite news |url=https://www.washingtonpost.com/world/india-is-the-first-asian-nation-to-touch-mars-orbit-joins-elite-global-space-club/2014/09/23/b6bc6992-a432-4f1e-87ad-5d6fc4da3460_story.html |title=India becomes first Asian nation to reach Mars orbit, joins elite global space club |newspaper= The Washington Post |date=24 September 2014 |access-date=24 September 2014 |quote=India became the first Asian nation to reach the Red Planet when its indigenously made unmanned spacecraft entered the orbit of Mars on Wednesday}}</ref><ref>{{cite news |url=http://edition.cnn.com/2014/09/23/world/asia/mars-india-orbiter/index.html |title=India's spacecraft reaches Mars orbit ... and history |work=CNN |date=24 September 2014 |access-date= |quote=India's Mars Orbiter Mission successfully entered Mars' orbit Wednesday morning, becoming the first nation to arrive on its first attempt and the first Asian country to reach the Red Planet. |last = Park|first = Madison }}</ref><ref name="NYT-20140924-GH">{{cite news |last=Harris |first=Gardiner |title=On a Shoestring, India Sends Orbiter to Mars on Its First Try |url=https://www.nytimes.com/2014/09/25/world/asia/on-a-shoestring-india-sends-orbiter-to-mars.html |date=24 September 2014 |work={{wipe|The New York Times}}|access-date=25 September 2014 }}</ref> is one of the least expensive interplanetary missions ever undertaken with an approximate total cost of {{INR}} 450 [[Crore]] ({{US$|73 million}}).<ref name="ibtimes20131105">{{cite news |url=http://www.ibtimes.co.in/india-successfully-launches-first-mission-to-mars-pm-congratulates-isro-team-photos-519719 |title=India Successfully Launches First Mission to Mars; PM Congratulates ISRO Team |work=International Business Times |date=5 November 2013 |access-date=13 October 2014}}</ref><ref name="ndtv20131105">{{cite news |url=http://www.ndtv.com/article/cheat-sheet/india-s-450-crore-mission-to-mars-to-begin-today-10-facts-441410 |title=India's 450-crore mission to Mars to begin today: 10 facts |work=NDTV |first=Abhinav |last=Bhatt |date=5 November 2013 |access-date=13 October 2014}}</ref> The first mission to Mars by any Arab country has been taken up by the United Arab Emirates. Called the [[Astronomy:Emirates Mars Mission|Emirates Mars Mission]], it was launched on 19 July 2020 and went into orbit around Mars on 9 February 2021. The uncrewed exploratory probe was named "Hope Probe" and was sent to Mars to study its atmosphere in detail.<ref>{{Cite web |title=Hope Mars Probe |url=http://mbrsc.ae/en/page/mars-probe |publisher=Mohammed Bin Rashid Space Centre |website=mbrsc.ae |access-date=22 July 2016 |archive-date=25 July 2016 |archive-url=https://web.archive.org/web/20160725185416/http://mbrsc.ae/en/page/mars-probe |url-status=dead }}</ref>

==== Phobos ====
{{Main|Astronomy:Exploration of Phobos}}
The Russian space mission [[Astronomy:Fobos-Grunt|Fobos-Grunt]], which launched on 9 November 2011 experienced a failure leaving it stranded in [[Astronomy:Low Earth orbit|low Earth orbit]].<ref name="noburn">{{cite web |url=http://www.satobs.org/seesat/Nov-2011/0069.html |title=Phobos-Grunt – serious problem reported |first=Ted |last=Molczan |publisher=[[Organization:SeeSat-L|SeeSat-L]] |date=9 November 2011 |access-date=9 November 2011 }}</ref> It was to begin exploration of the [[Astronomy:Phobos (moon)|Phobos]] and Martian circumterrestrial orbit, and study whether the moons of Mars, or at least Phobos, could be a "trans-shipment point" for spaceships traveling to Mars.<ref name="yt-W0cUvK0Dgy8">{{cite web|url=https://www.youtube.com/watch?v=W0cUvK0Dgy8 |title=Project Phobos-Grunt |publisher=YouTube |date=22 August 2006 |access-date=24 May 2012 }}</ref><!-- Remove groundless conjecture: It will study Phobos as a target of colonization, too.{{Citation needed|date=November 2008}}-->

===Asteroids===
[[File:Dawn-image-070911.jpg|thumb|Asteroid 4 Vesta, imaged by the ''Dawn'' spacecraft (2011)]]
Until the advent of [[Engineering:Spaceflight|space travel]], objects in the [[Astronomy:Asteroid belt|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 ''[[Engineering:Galileo (spacecraft)|Galileo]]'', which flew past two: [[Astronomy:951 Gaspra|951 Gaspra]] in 1991, followed by [[Astronomy:243 Ida|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 ''[[Astronomy:NEAR Shoemaker|NEAR Shoemaker]]'' probe in 2000, following an orbital survey of the object, [[Astronomy:433 Eros|433 Eros]]. The dwarf planet [[Astronomy:Ceres (dwarf planet)|Ceres]] and the asteroid [[Astronomy:4 Vesta|4 Vesta]], two of the three largest asteroids, were visited by NASA's [[Engineering:Dawn (spacecraft)|''Dawn'' spacecraft]], launched in 2007.

''Hayabusa'' was a [[Engineering:Robotic spacecraft|robotic spacecraft]] developed by the Japan Aerospace Exploration Agency to return a sample of material from the small near-Earth asteroid [[Astronomy:25143 Itokawa|25143 Itokawa]] to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, ''Hayabusa'' studied the asteroid's shape, spin, topography, color, composition, density, and history. In November 2005, it landed on the asteroid twice to collect samples. The spacecraft returned to Earth on 13 June 2010.

===Jupiter===
{{Main|Astronomy:Exploration of Jupiter}}
[[File:Io Tupan Patera.jpg|thumb|[[Earth:Tupan Patera|Tupan Patera]] on Io]]
The exploration of [[Astronomy:Jupiter|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; such as in [[Astronomy:Pioneer program|Pioneer]] and [[Astronomy:Voyager program|Voyager]] programs. The ''Galileo'' and ''Juno'' spacecraft are the only spacecraft to have entered the planet's orbit. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is precluded.

Reaching Jupiter from Earth requires a delta-v of 9.2&nbsp;km/s,<ref name="delta-v">{{cite web |last=Wong |first=Al |date=28 May 1998 |url=http://www2.jpl.nasa.gov/galileo/faqnav.html |archive-url=https://web.archive.org/web/19970105184300/http://www.jpl.nasa.gov/galileo/faqnav.html |url-status=dead |archive-date=5 January 1997 |title=Galileo FAQ: Navigation |publisher=NASA |access-date=28 November 2006 }}</ref> which is comparable to the 9.7&nbsp;km/s delta-v needed to reach low Earth orbit.<ref name="pma-delta">{{cite web |last=Hirata |first=Chris |url=http://www.pma.caltech.edu/~chirata/deltav.html |title=Delta-V in the Solar System |publisher=California Institute of Technology |access-date=28 November 2006 |archive-url=https://web.archive.org/web/20060715015836/http://www.pma.caltech.edu/~chirata/deltav.html |archive-date=15 July 2006 }}</ref> Fortunately, gravity assists through [[Engineering:Planetary flyby|planetary flyby]]s can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.<ref name="delta-v" />

Jupiter has 95 [[Astronomy:Moons of Jupiter|known moons]], many of which have relatively little known information about them.

===Saturn===
{{Main|Astronomy:Exploration of Saturn}}
[[Astronomy:Saturn|Saturn]] has been explored only through uncrewed spacecraft launched by NASA, including one mission (''[[Astronomy:Cassini–Huygens|Cassini–Huygens]]'') planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by ''[[Astronomy:Pioneer 11|Pioneer 11]]'', in 1980 by ''[[Astronomy:Voyager 1|Voyager 1]]'', in 1982 by ''[[Astronomy:Voyager 2|Voyager 2]]'' and an orbital mission by the ''Cassini'' spacecraft, which lasted from 2004 until 2017.

Saturn has at least 62 [[Astronomy:Moons of Saturn|known moons]], 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 [[Astronomy:Titan (moon)|Titan]], which holds the distinction of being the only moon in the Solar System with an atmosphere denser and thicker than that of Earth.  Titan holds the distinction of being the only object in the Outer Solar System that has been explored with a lander, the ''Huygens'' probe deployed by the ''Cassini'' spacecraft.

===Uranus===
{{Main|Astronomy:Exploration of Uranus}}
The exploration of [[Astronomy:Uranus|Uranus]] has been entirely through the ''[[Astronomy:Voyager 2|Voyager 2]]'' spacecraft, with no other visits currently planned. Given its [[Astronomy:Axial tilt|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 24 January 1986. ''Voyager 2'' studied the planet's unique atmosphere and [[Astronomy:Magnetosphere|magnetosphere]]. ''Voyager 2'' also examined its [[Astronomy:Rings of Uranus|ring system]] and the [[Astronomy:Moons of Uranus|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 unique, being 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 [[Astronomy:Miranda (moon)|Miranda]] had been unusually geologically active.

===Neptune===

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, the spacecraft found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous [[Astronomy:Great Dark Spot|anticyclone storm system]] rivaled in size only by Jupiter's [[Astronomy:Great Red Spot|Great Red Spot]]. Neptune also proved to have the fastest winds of any planet in the Solar System, measured as high as 2,100&nbsp;km/h.<ref name="Suomi1991">{{cite journal |last1=Suomi |first1=V.E. |last2=Limaye |first2=S.S. |last3=Johnson |first3=D.R. |title=High winds of Neptune: A possible mechanism |journal=Science |year=1991 |volume=251 |pages=929–932 |bibcode=1991Sci...251..929S  |doi=10.1126/science.251.4996.929 |pmid=17847386 |issue=4996 |s2cid=46419483 }}</ref> ''Voyager 2'' also examined [[Astronomy:Rings of Neptune|Neptune's ring]] and [[Astronomy:Moons of Neptune|moon system]]. It discovered 900 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, [[Astronomy:Proteus (moon)|Proteus]], proved to be the last largest moon in the system. Data from ''Voyager 2'' supported the view that Neptune's largest moon, [[Astronomy:Triton (moon)|Triton]], is a captured [[Astronomy:Kuiper belt|Kuiper belt]] object.<ref name="Agnor06">{{cite journal |last1=Agnor |first1=C.B. |last2=Hamilton |first2=D.P. |title=Neptune's capture of its moon Triton in a binary-planet gravitational encounter |journal=Nature |year=2006 |volume=441 |pages = 192–194 |doi=10.1038/nature04792 |pmid=16688170 |issue=7090 |bibcode=2006Natur.441..192A |s2cid=4420518 }}</ref>

===Pluto===

After an intense political battle, a mission to Pluto dubbed ''[[Astronomy:New Horizons|New Horizons]]'' was granted funding from the United States government in 2003.<ref name="s4p">{{cite web |title=Pluto mission gets green light at last |first=Robert |last=Roy Britt |work=space.com |url=http://www.space4peace.org/articles/plutomissiongetsok.htm |date=26 February 2003 |publisher=Space4Peace.org |access-date=26 December 2013 }}</ref> ''New Horizons'' was launched successfully on 19 January 2006. In early 2007 the craft made use of a [[Astronomy:Gravity assist|gravity assist]] from [[Astronomy:Jupiter|Jupiter]]. Its closest approach to Pluto was on 14 July 2015; scientific observations of Pluto began five months prior to closest approach and continued for 16 days after the encounter.

===Kuiper Belt Objects===
The ''New Horizons'' mission also did a flyby of the small planetesimal Arrokoth, in the [[Astronomy:Kuiper belt|Kuiper belt]], in 2019. This was its first extended mission.<ref>{{cite conference |title=New Horizons Kuiper Belt Extended Mission |url=http://pluto.jhuapl.edu/News-Center/Press-Conferences/2017-12-12/resources/2017_NH_AGU_PA.pdf |first1=Jim |last1=Green |first2=S. Alan |last2=Stern |date=12 December 2017 |conference=2017 AGU Fall Meeting |publisher=Applied Physics Laboratory |pages=12–15 |access-date=26 December 2018 |archive-url=https://web.archive.org/web/20181226234838/http://pluto.jhuapl.edu/News-Center/Press-Conferences/2017-12-12/resources/2017_NH_AGU_PA.pdf
|archive-date=26 December 2018 |url-status=dead |df= dmy-all}}</ref>

===Comets===
{{Main|Astronomy:List of missions to comets}}
[[File:Comet Hartley 2.jpg|thumb|Comet 103P/Hartley (2010)]]

Although many comets have been studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. In 1985, the ''[[Astronomy:International Cometary Explorer|International Cometary Explorer]]'' conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the [[Astronomy:Halley Armada|Halley Armada]] studying the famous comet. The [[Engineering:Deep Impact (spacecraft)|''Deep Impact'' probe]] smashed into 9P/Tempel to learn more about its structure and composition and the [[Engineering:Stardust (spacecraft)|''Stardust'' mission]] returned samples of another comet's tail. The [[Engineering:Philae (spacecraft)|''Philae'' lander]] successfully landed on Comet Churyumov–Gerasimenko in 2014 as part of the broader [[Engineering:Rosetta (spacecraft)|''Rosetta'' mission]].

===Deep space exploration===
{{main|Astronomy:Deep space exploration}}
[[Image:Hubble ultra deep field high rez edit1.jpg|thumb|This high-resolution image of the Hubble Ultra Deep Field includes galaxies of various ages, sizes, shapes, and colors. The smallest, reddest galaxies, are some of the most distant galaxies to have been imaged by an optical telescope.]]

Deep space exploration is the branch of [[Astronomy:Astronomy|astronomy]], [[Earth:Astronautics|astronautics]] and [[Engineering:Space technology|space technology]] that is involved with the exploration of distant regions of outer space.<ref>{{cite web|url=http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html |title=Space and its Exploration: How Space is Explored |work=NASA.gov |access-date=2009-07-01 |url-status=dead |archive-url=https://web.archive.org/web/20090702153058/http://adc.gsfc.nasa.gov/adc/education/space_ex/exploration.html |archive-date=2 July 2009 }}</ref> Physical exploration of space is conducted both by [[Astronomy:Human spaceflight|human spaceflight]]s (deep-space astronautics) and by [[Engineering:Robotic spacecraft|robotic spacecraft]].

Some of the best candidates for future deep space engine technologies include anti-matter, [[Physics:Nuclear power|nuclear power]] and [[Astronomy:Beam-powered propulsion|beamed propulsion]].<ref>{{cite web |url=http://www.bbc.co.uk/science/space/exploration/futurespaceflight/index.shtml |title=Future Spaceflight |work=BBC |access-date=2009-07-01 |archive-date=22 April 2009 |archive-url=https://web.archive.org/web/20090422162750/http://www.bbc.co.uk/science/space/exploration/futurespaceflight/index.shtml |url-status=dead }}</ref> The latter, beamed propulsion, appears to be the best candidate for deep space exploration presently available, since it uses known physics and known technology that is being developed for other purposes.<ref name="Forward1996">{{cite journal |title=Ad Astra! |journal=Journal of the British Interplanetary Society |first=Robert L |last=Forward |volume=49 |pages=23–32 |date=January 1996 |bibcode = 1996JBIS...49...23F }}</ref>

==Future of space exploration==
{{main|Astronomy:Future of space exploration}}
[[File:Innovative Interstellar Explorer interstellar space probe .jpg|thumb|Concept art for a NASA Vision mission]]
[[File:Rocket launch from Saturn moon.jpg|thumb|Artistic image of a rocket lifting from a Saturn moon]]

=== Breakthrough Starshot ===
{{main|Astronomy:Breakthrough Starshot}}
Breakthrough Starshot is a research and engineering project by the [[Astronomy:Breakthrough Initiatives|Breakthrough Initiatives]] to develop a proof-of-concept fleet of light sail spacecraft named ''StarChip'',<ref name="CD-20160412">{{cite web |last=Gilster |first=Paul |title=Breakthrough Starshot: Mission to Alpha Centauri |url=http://www.centauri-dreams.org/?p=35402 |date=12 April 2016 |work=Centauri Dreams |access-date=14 April 2016 }}</ref> to be capable of making the journey to the [[Astronomy:Alpha Centauri|Alpha Centauri]] star system 4.37 light-years away. It was founded in 2016 by [[Biography:Yuri Milner|Yuri Milner]], [[Biography:Stephen Hawking|Stephen Hawking]], and Mark Zuckerberg.<ref>{{Cite news|url=https://www.natureworldnews.com/articles/20799/20160414/stephen-hawking-mark-zuckerberg-and-russian-millionaire-yuri-milner-launch-100m-space-project-called-breakthrough-starshot.htm|title=Stephen Hawking, Mark Zuckerberg, Yuri Milner Launch $100M Space Project Called Breakthrough Starshot|last=F|first=Jessica|date=14 April 2016|work=Nature World News}}</ref><ref>{{Cite web|url=https://www.newsweek.com/mark-zuckerberg-joins-100-million-initiative-send-tiny-space-probes-explore-447513|title=Mark Zuckerberg Launches $100 Million Initiative To Send Tiny Space Probes To Explore Stars|last=Lee|first=Seung|date=13 April 2016|website=Newsweek|language=en|access-date=29 July 2019}}</ref>

=== Asteroids ===
An article in science magazine ''Nature'' suggested the use of asteroids as a gateway for space exploration, with the ultimate destination being Mars. In order to make such an approach viable, three requirements need to be fulfilled: first, "a thorough asteroid survey to find thousands of nearby bodies suitable for astronauts to visit"; second, "extending flight duration and distance capability to ever-increasing ranges out to Mars"; and finally, "developing better robotic vehicles and tools to enable astronauts to explore an asteroid regardless of its size, shape or spin". Furthermore, using asteroids would provide astronauts with protection from galactic cosmic rays, with mission crews being able to land on them without great risk to radiation exposure.

=== James Webb Space Telescope ===
{{Main|Astronomy:James Webb Space Telescope}}
The James Webb Space Telescope (JWST or "Webb") is a [[Astronomy:Space telescope|space telescope]] that is the successor to the [[Astronomy:Hubble Space Telescope|Hubble Space Telescope]].<ref name="about">{{cite web | url=https://jwst.nasa.gov/about.html | title=About the James Webb Space Telescope | access-date=13 January 2012}}</ref><ref>{{cite web|url=https://jwst.nasa.gov/comparison.html|publisher=JWST Home – NASA|title=How does the Webb Contrast with Hubble?|date=2016|access-date=4 December 2016|url-status=dead|archive-url=https://web.archive.org/web/20161203014957/http://jwst.nasa.gov/comparison.html|archive-date=3 December 2016}}</ref> The JWST will provide greatly improved resolution and sensitivity over the Hubble, and will enable a broad range of investigations across the fields of [[Astronomy:Astronomy|astronomy]] and [[Astronomy:Cosmology|cosmology]], including observing some of the most distant events and objects in the [[Astronomy:Universe|universe]], such as the [[Astronomy:Galaxy formation and evolution|formation of the first galaxies]]. Other goals include understanding the formation of stars and planets, and [[Astronomy:List of directly imaged exoplanets|direct imaging]] of exoplanets and [[Astronomy:Nova|nova]]s.<ref name="facts">{{cite web|url=https://jwst.nasa.gov/facts.html|title=JWST vital facts: mission goals|publisher=NASA James Webb Space Telescope|date=2017|access-date=29 January 2017}}</ref>

The primary mirror of the JWST, the Optical Telescope Element, is composed of 18 hexagonal mirror segments made of [[Chemistry:Gold|gold]]-plated [[Chemistry:Beryllium|beryllium]] which combine to create a {{convert|6.5|m|ft in|sp=us|adj=on}} diameter mirror that is much larger than the Hubble's {{convert|2.4|m|ft in|adj=on|sp=us}} mirror.  Unlike the Hubble, which observes in the near ultraviolet, [[Physics:Visible spectrum|visible]], and near infrared (0.1 to 1 μm) spectra, the JWST will observe in a lower frequency range, from long-wavelength visible light through [[Physics:Infrared|mid-infrared]] (0.6 to 27 μm), which will allow it to observe high [[Astronomy:Redshift|redshift]] objects that are too old and too distant for the Hubble to observe.<ref name="ReferenceB">{{cite web|url=http://www.stsci.edu/jwst/overview/history/1994|archive-url=https://wayback.archive-it.org/all/20140203162406/http://www.stsci.edu/jwst/overview/history/1994|url-status=dead|archive-date=3 February 2014|title=James Webb Space Telescope. JWST History: 1989–1994|publisher=Space Telescope Science Institute, Baltimore, MD|date=2017|access-date=29 December 2018}}</ref> The telescope must be kept very cold in order to observe in the infrared without interference, so it will be deployed in space near the Earth–Sun {{L2}} [[Astronomy:Lagrangian point|Lagrangian point]], and a large sunshield made of [[Chemistry:Silicon|silicon]]- and [[Chemistry:Aluminum|aluminum]]-coated [[Chemistry:Kapton|Kapton]] will keep its mirror and instruments below {{Convert|50|K|sigfig=2}}.<ref name=nasasunshield>{{cite web| title=The Sunshield| url=http://www.jwst.nasa.gov/sunshield.html| website=nasa.gov| publisher=[[Organization:NASA|NASA]]|access-date=28 August 2016}}</ref>

=== Artemis program ===
{{main|Astronomy:Artemis program}}
The Artemis program is an ongoing [[Astronomy:List of human spaceflight programs|crewed spaceflight program]] carried out by [[Organization:NASA|NASA]], U.S. [[Engineering:Private spaceflight|commercial spaceflight companies]], and international partners such as [[Organization:European Space Agency|ESA]],<ref name="Artemis home">{{Cite web|url=https://www.nasa.gov/specials/moontomars/index.html|title=NASA: Moon to Mars|website=NASA|access-date=19 May 2019}}</ref> with the goal of landing "the first woman and the next man" on the Moon, specifically at the [[Astronomy:Lunar south pole|lunar south pole]] region by 2024. Artemis would be the next step towards the long-term goal of establishing a sustainable presence on the Moon, laying the foundation for private companies to build a lunar economy, and eventually sending humans to [[Astronomy:Mars|Mars]].

In 2017, the lunar campaign was authorized by [[Organization:NASA#Space Policy Directive 1|Space Policy Directive 1]], utilizing various ongoing spacecraft programs such as [[Engineering:Orion (spacecraft)|Orion]], the [[Astronomy:Lunar Gateway|Lunar Gateway]], [[Astronomy:Commercial Lunar Payload Services|Commercial Lunar Payload Services]], and adding an undeveloped crewed lander. The [[Astronomy:Space Launch System|Space Launch System]] will serve as the primary launch vehicle for Orion, while commercial launch vehicles are planned for use to launch various other elements of the campaign.<ref name="Verge May2019">[https://www.theverge.com/2019/5/17/18627839/nasa-administrator-jim-bridenstine-artemis-moon-program-budget-amendment NASA administrator on new Moon plan: 'We're doing this in a way that's never been done before']. Loren Grush, ''The Verge''. 17 May 2019.</ref> NASA requested $1.6 billion in additional funding for Artemis for fiscal year 2020,<ref name='Harwood CBS'>{{cite news |last=Harwood |first=William |url=https://www.cbsnews.com/news/nasa-moon-mission-budget-administrator-jim-bridenstine/ |title=NASA boss pleads for steady moon mission funding |work=CBS News |date=17 July 2019 |access-date=28 August 2019}}</ref> while the Senate Appropriations Committee requested from NASA a five-year budget profile<ref>{{cite news|url=https://spacenews.com/senate-appropriators-advance-bill-funding-nasa-despite-uncertainties-about-artemis-costs/ |title=Senate appropriators advance bill funding NASA despite uncertainties about Artemis costs|first=Jeff |last=Foust |publisher=SpaceNews |date=27 September 2019|access-date=February 23, 2023}}</ref> which is needed for evaluation and approval by Congress.<ref>{{Cite web|url=https://qz.com/1618604/nasa-asks-for-1-6-billion-to-fund-artemis-moon-program/|title=Trump wants $1.6 billion for a moon mission and proposes to get it from college aid|last1=Fernholz|first1=Tim|website=Quartz|date=14 May 2019 |language=en|access-date=2019-05-14}}</ref><ref>{{Cite web|url=https://arstechnica.com/science/2019/05/nasa-reveals-funding-needed-for-moon-program-says-it-will-be-named-artemis/|title=NASA reveals funding needed for Moon program, says it will be named Artemis|last=Berger|first=Eric|date=2019-05-14|website=Ars Technica|language=en-us|access-date=2019-05-22}}</ref>

==Rationales==
{{Main|Engineering:Space advocacy}}
<!--- n.b. Anything added to this section that is unreferenced is going to be deleted!!!!! --->
[[File:Aldrin Apollo 11 original.jpg|thumb| Astronaut Buzz Aldrin 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 [[Organization:NASA|NASA]] and [[Company:Roscosmos|Roscosmos]], is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.<ref name="doi-1023">{{Cite journal | doi = 10.1023/A:1020207506064| pmid = 14983842| year = 2002| last1 = Hertzfeld | first1 = H. R. | journal = The Journal of Technology Transfer| volume = 27| issue = 4| pages = 311–320|title=Measuring the Economic Returns from Successful NASA Life Sciences Technology Transfers| s2cid = 20304464}}</ref> It is also argued that space exploration would lead to the extraction of resources on other planets and especially asteroids, which contain billions of dollars worth of minerals and metals. Such expeditions could generate a lot of revenue.<ref name="nature-2012">{{cite journal |last=Elvis |first=Martin |title=Let's mine asteroids – for science and profit |year=2012 |journal=Nature |volume=485 |issue=7400 |page=549 |doi=10.1038/485549a |pmid=22660280 |bibcode=2012Natur.485..549E |doi-access=free }}</ref> In addition, it has been argued that space exploration programs help inspire youth to study in science and engineering.<ref name="freakonomics">{{cite web |url=http://freakonomics.com/2008/01/11/is-space-exploration-worth-the-cost-a-freakonomics-quorum/ |title=Is Space Exploration Worth the Cost? A Freakonomics Quorum |work=Freakonomics |publisher=freakonomics.com |access-date=27 May 2014 |date=2008-01-11 }}</ref> Space exploration also gives scientists the ability to perform experiments in other settings and expand humanity's knowledge.<ref>{{Cite journal|last1=Zelenyi|first1=L. M.|last2=Korablev|first2=O. I.|last3=Rodionov|first3=D. S.|last4=Novikov|first4=B. S.|last5=Marchenkov|first5=K. I.|last6=Andreev|first6=O. N.|last7=Larionov|first7=E. V.|date=December 2015|title=Scientific objectives of the scientific equipment of the landing platform of the ExoMars-2018 mission|journal=Solar System Research|language=en|volume=49|issue=7|pages=509–517|doi=10.1134/S0038094615070229|issn=0038-0946|bibcode=2015SoSyR..49..509Z|s2cid=124269328}}</ref>

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to [[Unsolved:Human extinction|extinction]]. Some of the reasons are lack of natural resources, comets, nuclear war, and worldwide epidemic. [[Biography:Stephen Hawking|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."<ref name="tele-20011016">{{cite news |url=https://www.telegraph.co.uk/news/main.jhtml?xml=/news/2001/10/16/nhawk16.xml |archive-url=https://web.archive.org/web/20040125082643/http://www.telegraph.co.uk/news/main.jhtml?xml=%2Fnews%2F2001%2F10%2F16%2Fnhawk16.xml |url-status=dead |archive-date=25 January 2004 |work=The Daily Telegraph |title=Colonies in space may be only hope, says Hawking |date=15 October 2001 |access-date=5 August 2007 |location=London |first=Roger |last=Highfield }}</ref> [[Biography:Arthur C. Clarke|Arthur C. Clarke]] (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph ''Interplanetary Flight''.<ref name="intro-ast">{{cite book|title=Interplanetary Flight – An Introduction to Astronautics|last=Clarke|first=Arthur C.|publisher=Harper & Brothers|year=1950|location=New York|chapter=10}}</ref> He argued that humanity's choice is essentially between expansion off Earth into space, versus cultural (and eventually biological) stagnation and death.
These motivations could be attributed to one of the first rocket scientists in NASA, [[Biography:Wernher von Braun|Wernher von Braun]], and his vision of humans moving beyond Earth. The basis of this plan was to:

<blockquote>Develop multi-stage rockets capable of placing satellites, animals, and humans in space.

Development of large, winged reusable spacecraft capable of carrying humans and equipment into Earth orbit in a way that made space access routine and cost-effective.

Construction of a large, permanently occupied space station to be used as a platform both to observe Earth and from which to launch deep space expeditions.

Launching the first human flights around the Moon, leading to the first landings of humans on the Moon, with the intent of exploring that body and establishing permanent lunar bases.

Assembly and fueling of spaceships in Earth orbit for the purpose of sending humans to Mars with the intent of eventually colonizing that planet.<ref name="doi:10.1016">{{Cite journal | year = 2007| last1 = Launius | first1 = R. D. | last2 = Mccurdy |  first2 =  H. E. | journal = Technology in Society| volume = 29| issue = 3| pages = 271–282|title=Robots and humans in space flight: Technology, evolution, and interplanetary travel | doi = 10.1016/j.techsoc.2007.04.007 }}</ref></blockquote>

Known as the Von Braun Paradigm, the plan was formulated to lead humans in the exploration of space. Von Braun's vision of human space exploration served as the model for efforts in space exploration well into the twenty-first century, with NASA incorporating this approach into the majority of their projects.<ref name="doi:10.1016" /> The steps were followed out of order, as seen by the Apollo program reaching the moon before the space shuttle program was started, which in turn was used to complete the International Space Station. Von Braun's Paradigm formed NASA's drive for human exploration, in the hopes that humans discover the far reaches of the universe.

NASA has produced a series of public service announcement videos supporting the concept of space exploration.<ref name="yt-EewrC22ysus">{{cite web |url=https://www.youtube.com/watch?v=EewrC22ysus |title=NASA "Reach" Public Service Announcement for Space Exploration |publisher=NASA }}</ref>

Overall, the public remains largely supportive of both crewed and uncrewed 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.<ref name="poll-2">{{cite web |url=http://www.pollingreport.com/space2.htm |publisher=Pollingreport.com |title=Origin of Human Life – USA Today/Gallup Poll |date=3 July 2007 |access-date=25 December 2013 }}</ref>

=== Human nature ===
[[Engineering:Space advocacy|Space advocacy]] and [[Social:Space policy|space policy]]<ref name="AtlanticDestiny">{{cite web |first=Marina |last=Koren |date=17 September 2020 |title=No One Should 'Colonize' Space |url=https://www.theatlantic.com/science/archive/2020/09/manifest-destiny-trump-space-exploration/612439/ |access-date=2 November 2020 |website=The Atlantic}}</ref> regularly invokes exploration as a [[Philosophy:Human nature|human nature]].<ref name="Destiny">{{cite web|url=http://www.anthropology-news.org/index.php/2019/07/12/destiny-in-space/|title=Destiny in Space|first=Deana L.|last=Weibel|date=12 July 2019|publisher=American Anthropological Association|access-date=2 December 2020|archive-date=31 October 2020|archive-url=https://web.archive.org/web/20201031100927/http://www.anthropology-news.org/index.php/2019/07/12/destiny-in-space/|url-status=dead}}</ref>

==Topics==
{{Main|Astronomy:Space science|Astronomy:Human presence in space}}

===Spaceflight===
{{Main|Engineering:Spaceflight|Earth:Astronautics}}
[[File:Delta-Vs for inner Solar System.svg|thumbnail|right|[[Astronomy:Delta-v budget|Delta-v's]] in km/s for various orbital maneuvers]]
''Spaceflight'' is the use of [[Engineering:Space technology|space technology]] to achieve the flight of [[Engineering:Spacecraft|spacecraft]] into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like [[Astronomy:Space tourism|space tourism]] and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, [[Astronomy:Reconnaissance satellite|reconnaissance satellite]]s and other [[Astronomy:Earth observation satellite|Earth observation satellite]]s.

A spaceflight typically begins with a [[Engineering:Rocket launch|rocket launch]], which provides the initial thrust to overcome the force of [[Physics:Gravity|gravity]] and propels the spacecraft from the surface of 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|Astronomy: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 [[Engineering:Spacecraft|spacecraft]] in orbit are also satellites.

===Commercialization of space===
The commercialization of space first started out with the launching of private satellites by NASA or other space agencies. Current examples of the commercial satellite use of space include satellite navigation systems, satellite television and [[Physics:Satellite radio|satellite radio]]. The next step of commercialization of space was seen as human spaceflight. Flying humans safely to and from space had become routine to NASA.<ref>year = 2002| last1 = Gregory | first1 = Frederick | last2 = Garber |  first2 =  S.J. | book = Looking Backward, Looking Forward: Forty Years of U.S. Human Spaceflight| pages = 73–80 |title=Making Human Spaceflight as Safe as Possible</ref> Reusable spacecraft were an entirely new engineering challenge, something only seen in novels and films like Star Trek and War of the Worlds. Great names like [[Biography:Buzz Aldrin|Buzz Aldrin]] supported the use of making a reusable vehicle like the space shuttle. Aldrin held that reusable spacecraft were the key in making space travel affordable, stating that the use of "passenger space travel is a huge potential market big enough to justify the creation of reusable launch vehicles".<ref>year = 2002| last1 = Aldrin | first1 = Buzz | last2 = Garber |  first2 =  S.J. | book = Looking Backward, Looking Forward: Forty Years of U.S. Human Spaceflight| pages = 91–100 |title=Apollo and Beyond</ref> How can the public go against the words of one of America's best known heroes in space exploration? After all exploring space is the next great expedition, following the example of Lewis and Clark.[[Astronomy:Space tourism|Space tourism]] is the next step reusable vehicles in the commercialization of space. The purpose of this form of [[Astronomy:Human spaceflight|space travel]] is used by individuals for the purpose of personal pleasure.

[[Engineering:Private spaceflight|Private spaceflight companies]] such as [[Company:SpaceX|SpaceX]] and [[Company:Blue Origin|Blue Origin]], and [[Astronomy:Orbital Technologies Commercial Space Station|commercial space stations]] such as the Axiom Space and the Bigelow Commercial Space Station have dramatically changed the landscape of space exploration, and will continue to do so in the near future.

===Alien life===
{{Main|Astronomy:Astrobiology|Astronomy:Extraterrestrial life}}
Astrobiology is the interdisciplinary study of life in the universe, combining aspects of [[Astronomy:Astronomy|astronomy]], [[Biology:Biology|biology]] and geology.<ref name="NASAastrobio">{{cite web |url=http://astrobiology.arc.nasa.gov/ |title=NASA Astrobiology |publisher=Astrobiology.arc.nasa.gov |access-date=24 May 2012 |url-status=dead |archive-url=https://web.archive.org/web/20150928003207/http://astrobiology.arc.nasa.gov/ |archive-date=28 September 2015}}</ref> It is focused primarily on the study of the origin, distribution and [[Biology:Evolution|evolution]] of life. It is also known as '''exobiology''' (from Greek: έξω, ''exo'', "outside").<ref name="aleph-x">{{cite web |url=http://www.aleph.se/Trans/Words/x.html |title=X |publisher=Aleph.se |date=11 March 2000 |access-date=24 May 2012 }}</ref><ref name="www-pho">{{cite web |url=http://www.worldwidewords.org/articles/phobias.htm |title=Fears and dreads |publisher=World Wide Words |date=31 May 1997 |access-date=24 May 2012 }}</ref><ref name="itw-1066">{{cite web |url=http://www.itwire.com.au/content/view/11647/1066/ |title=iTWire – Scientists will look for alien life, but Where and How? |publisher=Itwire.com.au |date=27 April 2007 |access-date=24 May 2012 |archive-url=https://web.archive.org/web/20081014092633/http://www.itwire.com.au/content/view/11647/1066/ |archive-date=14 October 2008 |url-status=dead}}</ref> The term "Xenobiology" has been used as well, but this is technically incorrect because its terminology means "biology of the foreigners".<ref name="bio-ast">{{cite web |url=http://biocab.org/Astrobiology.html |title=Astrobiology |publisher=Biocab.org |access-date=24 May 2012 |archive-date=12 December 2010 |archive-url=https://web.archive.org/web/20101212184044/http://biocab.org/Astrobiology.html |url-status=dead }}</ref> Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on Earth.<ref name="AstroDNA">{{cite web |title=Launching the Alien Debates |last=Ward |first=Peter |url=http://www.astrobio.net/debate/2168/launching-the-alien-debates |date=8 December 2006 |work=[[Astronomy:Astrobiology Magazine|Astrobiology Magazine]] |access-date=25 December 2013 |archive-url=https://web.archive.org/web/20201023105824/https://www.astrobio.net/extreme-life/launching-the-alien-debates/ |archive-date=2020-10-23 |url-status=usurped}}</ref> In the Solar System some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.<ref name="sc-extra">{{cite web|url=http://spacechronology.com/extra.html |archive-url=https://archive.today/20120714162249/http://spacechronology.com/extra.html |url-status=dead |archive-date=14 July 2012 |title=Astrobiology: the quest for extraterrestrial life |publisher=Spacechronology.com |date=29 September 2010 |access-date=24 May 2012 }}</ref>

===Human spaceflight and habitation===
[[File:Yury Usachev in Russian crew quarters.jpg|thumb|200px|Crew quarters on Zvezda, the base ISS crew module]]
To date, the longest human occupation of space is the [[Astronomy:International Space Station|International Space Station]] which has been in continuous use for {{age in years and days|2000|11|02}}. [[Biography:Valeri Polyakov|Valeri Polyakov]]'s record single spaceflight of almost 438 days aboard the [[Astronomy:Mir|Mir]] space station has not been surpassed. The health effects of space have been well documented through years of research conducted in the field of aerospace medicine. Analog environments similar to those one may experience in space travel (like deep sea submarines) have been used in this research to further explore the relationship between isolation and extreme environments.<ref name="Doarn 2019 190">{{Cite journal|last1=Doarn|first1=CharlesR|last2=Polk|first2=Jd|last3=Shepanek|first3=Marc|date=2019|title=Health challenges including behavioral problems in long-duration spaceflight|journal=Neurology India|language=en|volume=67|issue=8|pages=S190–S195|doi=10.4103/0028-3886.259116|pmid=31134909|s2cid=167219863|issn=0028-3886 |doi-access=free }}</ref> It is imperative that the health of the crew be maintained as any deviation from baseline may compromise the integrity of the mission as well as the safety of the crew, hence the reason why astronauts must endure rigorous medical screenings and tests prior to embarking on any missions. However, it does not take long for the environmental dynamics of spaceflight to commence its toll on the human body; for example, [[Astronomy:Space adaptation syndrome|space motion sickness (SMS)]] – a condition which affects the neurovestibular system and culminates in mild to severe signs and symptoms such as vertigo, dizziness, fatigue, nausea, and disorientation – plagues almost all space travelers within their first few days in orbit.<ref name="Doarn 2019 190"/> Space travel can also have a profound impact on the psyche of the crew members as delineated in anecdotal writings composed after their retirement. Space travel can adversely affect the body's natural biological clock ([[Biology:Circadian rhythm|circadian rhythm]]); sleep patterns causing sleep deprivation and fatigue; and social interaction; consequently, residing in a Low Earth Orbit (LEO) environment for a prolonged amount of time can result in both mental and physical exhaustion.<ref name="Doarn 2019 190"/> Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure. The lack of gravity causes fluid to rise upward which can cause pressure to build up in the eye, resulting in vision problems; the loss of bone minerals and densities; cardiovascular deconditioning; and decreased endurance and muscle mass.<ref>{{Cite web|url=http://www.nasa.gov/hrp/bodyinspace|title=The Human Body in Space|last=Perez|first=Jason|date=2016-03-30|website=NASA|access-date=2019-11-11}}</ref>

[[Physics:Radiation|Radiation]] is perhaps the most insidious health hazard to space travelers as it is invisible to the naked eye and can cause cancer. Space crafts are no longer protected from the sun's radiation as they are positioned above the Earth's magnetic field; the danger of radiation is even more potent when one enters deep space. The hazards of radiation can be ameliorated through protective shielding on the spacecraft, alerts, and [[Physics:Dosimetry|dosimetry]].<ref name="Mars">{{Cite web|url=http://www.nasa.gov/hrp/5-hazards-of-human-spaceflight|title=5 Hazards of Human Spaceflight|last=Mars|first=Kelli|date=2018-03-27|website=NASA|access-date=2019-10-06}}</ref>

Fortunately, with new and rapidly evolving technological advancements, those in [[Engineering:Mission control center|Mission Control]] are able to monitor the health of their [[Astronaut|astronaut]]s more closely utilizing [[Medicine:Telemedicine|telemedicine]]. One may not be able to completely evade the physiological effects of space flight, but they can be mitigated. For example, medical systems aboard space vessels such as the [[Astronomy:International Space Station|International Space Station (ISS)]] are well equipped and designed to counteract the effects of lack of gravity and weightlessness; on-board treadmills can help prevent muscle loss and reduce the risk of developing premature osteoporosis.<ref name="Doarn 2019 190"/><ref name="Mars"/> Additionally, a crew medical officer is appointed for each ISS mission and a flight surgeon is available 24/7 via the [[Engineering:Mission control center|ISS Mission Control Center]] located in Houston, Texas.<ref name="Mars"/> Although the interactions are intended to take place in real time, communications between the space and terrestrial crew may become delayed – sometimes by as much as 20 minutes<ref name="Mars"/> – as their distance from each other increases when the spacecraft moves further out of LEO; because of this the crew are trained and need to be prepared to respond to any medical emergencies that may arise on the vessel as the ground crew are hundreds of miles away. As one can see, travelling and possibly living in space poses many challenges. 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.<ref name="nasa-164021">{{cite press release |title=Global Exploration Strategy and Lunar Architecture |publisher=NASA |date=4 December 2006 |url=http://www.nasa.gov/pdf/164021main_lunar_architecture.pdf |access-date=5 August 2007 |archive-url=https://web.archive.org/web/20070614040311/http://www.nasa.gov/pdf/164021main_lunar_architecture.pdf |archive-date=14 June 2007 }}</ref>

Beyond the technical factors that could make living in space more widespread, it has been suggested that the lack of [[Finance:Private property|private property]], the inability or difficulty in establishing property rights in space, has been an impediment to the development of space for human habitation. Since the advent of [[Engineering:Space technology|space technology]] in the latter half of the twentieth century, the ownership of property in space has been murky, with strong arguments both for and against. In particular, the making of [[Earth:Sovereign state|national]] [[Earth:Land claim|territorial claims]] in [[Astronomy:Outer space|outer space]] and on celestial bodies has been specifically proscribed by the [[Engineering:Outer Space Treaty|Outer Space Treaty]], which had been, {{as of|2012|lc=y}}, ratified by all [[Engineering:Spacefaring|spacefaring nations]].<ref name="tna2012fall">{{cite journal|last=Simberg |first=Rand |title=Property Rights in Space |journal=The New Atlantis |date=Fall 2012 |issue=37 |pages=20–31 |url=http://www.thenewatlantis.com/publications/property-rights-in-space |access-date=14 December 2012 |url-status=dead |archive-url=https://web.archive.org/web/20121215001750/http://www.thenewatlantis.com/publications/property-rights-in-space |archive-date=15 December 2012 }}</ref>
Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human [[Astronomy:Space habitat|habitation]] of locations outside Earth, especially of natural satellites or planets such as the [[Astronomy:Colonization of the Moon|Moon]] or [[Astronomy:Colonization of Mars|Mars]], using significant amounts of in-situ resource utilization.

==== Human representation and participation ====

Participation and representation of humanity in space is an issue ever since the first phase of space exploration.<ref name="Durrani"/> Some rights of non-spacefaring countries have been mostly secured through international [[Astronomy:Space law|space law]], declaring space the "[[Social:Common heritage of mankind|province of all mankind]]", understanding [[Engineering:Spaceflight|spaceflight]] as its resource, though sharing of space for all humanity is still criticized as [[Social:Imperialism|imperialist]] and lacking.<ref name="Durrani">{{cite magazine |url=https://www.thenation.com/article/archive/apollo-space-lunar-rockets-colonialism/ |title=Is Spaceflight Colonialism? |magazine=The Nation|first=Haris |last=Durrani |access-date=2 October 2020 |date=19 July 2019}}</ref> Additionally to international inclusion, the inclusion of women and people of colour has also been lacking. To reach a more inclusive spaceflight some organizations like the ''Justspace Alliance''<ref name="Durrani"/> and IAU featured ''Inclusive Astronomy''<ref>{{Cite web |url=https://www.inclusiveastronomy.org/ |title=Website of the IAU100 ''Inclusive Astronomy'' project |access-date=8 January 2022 |archive-date=22 December 2021 |archive-url=https://web.archive.org/web/20211222220447/https://www.inclusiveastronomy.org/ |url-status=dead }}</ref> have been formed in recent years.

=====Women=====
{{Main|Astronomy:Women in space}}
The first woman to go to space was [[Biography:Valentina Tereshkova|Valentina Tereshkova]]. She flew in 1963 but it was not until the 1980s that another woman entered space again. All astronauts were required to be military test pilots at the time and women were not able to join this career, this is one reason for the delay in allowing women to join space crews.{{citation needed|date=June 2020}} After the rule changed, [[Biography:Svetlana Savitskaya|Svetlana Savitskaya]] became the second woman to go to space, she was also from the [[Place:Soviet Union|Soviet Union]]. [[Biography:Sally Ride|Sally Ride]] became the next woman in space and the first woman to fly to space through the United States program.

Since then, eleven other countries have allowed women astronauts. The first all-female space walk occurred in 2018, including [[Biography:Christina Koch|Christina Koch]] and Jessica Meir. They had both previously participated in space walks with NASA. The first woman to go to the Moon is planned for 2024.

Despite these developments women are still underrepresented among astronauts and especially cosmonauts. Issues that block potential applicants from the programs, and limit the space missions they are able to go on, include:
* agencies limiting women to half as much time in space than men, arguing with unresearched potential risks for cancer.<ref>{{cite web | url = http://www.space.com/22252-women-astronauts-radiation-risk.html | title = Female Astronauts Face Discrimination from Space Radiation Concerns, Astronauts Say | first = Miriam | last = Kramer | date = 27 August 2013 | access-date = 7 January 2017 | work = Space.com | publisher = Purch}}</ref>
* a lack of space suits sized appropriately for female astronauts.<ref name="clothing">{{cite magazine |last=Sokolowski |first=Susan L.|title= Female astronauts: How performance products like space suits and bras are designed to pave the way for women's accomplishments|url=https://theconversation.com/female-astronauts-how-performance-products-like-space-suits-and-bras-are-designed-to-pave-the-way-for-womens-accomplishments-114346 |date=5 April 2019 | magazine =The Conversation |access-date=10 May 2020 }}</ref>

===Art===

Artistry in and from space ranges from signals, capturing and arranging material like [[Biography:Yuri Gagarin|Yuri Gagarin]]'s [[Philosophy:Selfie|selfie]] in space or the image [[Astronomy:The Blue Marble|The Blue Marble]], over drawings like the first one in space by cosmonaut and artist Alexei Leonov, music videos like Chris Hadfield's cover of Space Oddity on board the ISS, to permanent installations on celestial bodies like [[Astronomy:Moon#Human impact|on the Moon]].

==See also==
{{Main|Astronomy:Outline of space exploration}}
* [[Astronomy:Discovery and exploration of the Solar System|Discovery and exploration of the Solar System]]
* [[Astronomy:Spacecraft propulsion|Spacecraft propulsion]]
* [[Engineering:List of crewed spacecraft|List of crewed spacecraft]]
* [[Astronomy:List of missions to Mars|List of missions to Mars]]
* [[Astronomy:List of missions to the outer planets|List of missions to the outer planets]]
* [[Engineering:List of landings on extraterrestrial bodies|List of landings on extraterrestrial bodies]]
* [[Astronomy:List of spaceflight records|List of spaceflight records]]

===Robotic space exploration programs===
{{Div col|colwidth=22em}}
* [[Engineering:Robotic spacecraft|Robotic spacecraft]]
* Timeline of planetary exploration
* Landings on other planets
* [[Astronomy:Pioneer program|Pioneer program]]
* Luna program
* [[Astronomy:Zond program|Zond program]]
* Venera program
* Mars probe program
* [[Engineering:Ranger program|Ranger program]]
* [[Astronomy:Mariner program|Mariner program]]
* [[Astronomy:Surveyor program|Surveyor program]]
* [[Engineering:Viking program|Viking program]]
* [[Astronomy:Voyager program|Voyager program]]
* [[Astronomy:Vega program|Vega program]]
* [[Astronomy:Phobos program|Phobos program]]
* Discovery program
* [[Astronomy:Chandrayaan-1|Chandrayaan Program]]
* [[Astronomy:Mars Orbiter Mission|Mangalyaan Program]]
* [[Astronomy:Chinese Lunar Exploration Program|Chang'e Program]]
* Private [[Company:Astrobotic Technology|Astrobotic Technology]] Program
{{Div col end}}

===Living in space===
* [[Astronomy:Interplanetary contamination|Interplanetary contamination]]

====Animals in space====
{{Div col|colwidth=22em}}
* Animals in space
* Monkeys in space
* Russian space dogs
{{Div col end}}

====Humans in space====
{{Div col|colwidth=22em}}
* [[Astronaut]]s
* [[Astronomy:List of human spaceflights|List of human spaceflights]]
* List of human spaceflights by program
* Vostok program
* Mercury program
* Voskhod program
* Gemini program
* Soyuz program
* [[Astronomy:Apollo program|Apollo program]]
* Salyut program
* [[Engineering:Skylab|Skylab]]
* [[Engineering:Space Shuttle program|Space Shuttle program]]
* [[Astronomy:Mir|Mir]]
* [[Astronomy:International Space Station|International Space Station]]
* [[Astronomy:Vision for Space Exploration|Vision for Space Exploration]]
* Aurora Programme
* [[Astronomy:Scaled Composites Tier One|Tier One]]
* [[Astronomy:Effect of spaceflight on the human body|Effect of spaceflight on the human body]]
* [[Engineering:Space architecture|Space architecture]]
* {{annotated link|Research station}}
* Space archaeology
* [[Astronomy:Flexible path|flexible path]] destinations set
{{Div col end}}

===Recent and future developments===
{{Div col|colwidth=22em}}
* [[Biography:Commercial astronaut|Commercial astronaut]]s
* [[Astronomy:Artemis program|Artemis program]]
* [[Physics:Energy development|Energy development]]
* [[Astronomy:Exploration of Mars|Exploration of Mars]]
* [[Astronomy:Space tourism|Space tourism]]
* [[Engineering:Private spaceflight|Private spaceflight]]
* [[Engineering:Space colonization|Space colonization]]
* Interstellar spaceflight
* [[Astronomy:Deep space exploration|Deep space exploration]]
* Human outpost
* [[Astronomy:Mars to Stay|Mars to Stay]]
* [[Company:NewSpace|NewSpace]]
* [[Astronomy:NASA lunar outpost concepts|NASA lunar outpost concepts]]
{{Div col end}}

===Other===
{{Div col|colwidth=22em}}
* List of spaceflights
* [[Astronomy:Timeline of Solar System exploration|Timeline of Solar System exploration]]
* [[Astronomy:List of artificial objects on extra-terrestrial surfaces|List of artificial objects on extra-terrestrial surfaces]]
* Space station
* [[Astronomy:Space telescope|Space telescope]]
* Sample return mission
* Atmospheric reentry
* [[Medicine:Space and survival|Space and survival]]
* [[Astronomy:List of spaceflight-related accidents and incidents|List of spaceflight-related accidents and incidents]]
* [[Engineering:Religion in space|Religion in space]]
* [[Engineering:Militarisation of space|Militarisation of space]]
* French space program
* Russian explorers
* [[Astronomy:U.S. space exploration history on U.S. stamps|U.S. space exploration history on U.S. stamps]]
* [[Deep-sea exploration]]
* Arctic exploration
{{Div col end}}

==References==
{{Reflist}}

==Further reading==
{{refbegin}}
* {{cite journal |title=Spaceflight: The Development of Science, Surveillance, and Commerce in Space |journal=[[Proceedings of the IEEE]] |last=Launius |first=R.D. |display-authors=0 |volume=100 |issue=special centennial issue |pages=1785–1818 |doi=10.1109/JPROC.2012.2187143 |year=2012 |doi-access=free }} An overview of the history of space exploration and predictions for the future.
{{refend}}

==External links==
{{Library resources box}}
* [http://www.high-frontier.org Building a Spacefaring Civilization] {{Webarchive|url=https://web.archive.org/web/20190522210829/http://www.high-frontier.org/ |date=22 May 2019 }}
* [http://spacechronology.com Chronology of space exploration, astrobiology, exoplanets and news] {{Webarchive|url=https://web.archive.org/web/20200929160331/http://spacechronology.com/ |date=29 September 2020 }}
* [http://www.spaceref.com Space related news]
* [http://www.sen.com Space Exploration Network]
* [http://spaceflight.nasa.gov NASA's website on human space travel]
* [https://www.nasa.gov/topics/technology/space-travel/index.html NASA's website on space exploration technology]
* [http://www.nps.gov/history/NR/twhp/wwwlps/lessons/101space/101space.htm "America's Space Program: Exploring a New Frontier", a National Park Service Teaching with Historic Places (TwHP) lesson plan]
* [http://spacephotos.ru/ The Soviet-Russian Spaceflight's History Photoarchive]
* [http://www.life.com/image/first/in-gallery/30222/the-21-greatest-space-photos-ever The 21 Greatest Space Photos Ever] {{Webarchive|url=https://web.archive.org/web/20101227233620/http://www.life.com/image/first/in-gallery/30222/the-21-greatest-space-photos-ever |date=27 December 2010 }} – slideshow by ''Life Magazine''
* "[http://www.phy6.org/stargaze/Sintro.htm From Stargazers to Starships]", extensive educational web site and course covering spaceflight, astronomy and related physics
* [https://www.youtube.com/watch?v=e7DEw70LVWs ''We Are The Explorers''], NASA Promotional Video ([http://www.nasa.gov/home/hqnews/2012/mar/HQ_12_071_We_Explore_Video.txt Press Release])

{{Planetary exploration}}
{{Space exploration lists and timelines}}
{{navboxes | title = Related topics | list1  = 
{{In space}}
{{Public sector space agencies}}
{{Solar System}}
{{Spaceflight}}
{{Spacecraft by destination}}
}}

[[Category:Space exploration| ]]
[[Category:Spaceflight|Exploration]]

{{Sourceattribution|Space exploration}}