132-406: NASA's large strategic science missions or large strategic missions , formerly known as Flagship missions or Flagship-class missions , are the costliest and most capable NASA science spacecraft. Flagship missions exist within all four divisions of NASA's Science Mission Directorate (SMD): the astrophysics , Earth science , heliophysics and planetary science divisions. "Large" refers to
264-523: A planetary nebula , returning some of the material that formed the Sun—but now enriched with heavier elements like carbon—to the interstellar medium . Astronomers sometimes divide the Solar System structure into separate regions. The inner Solar System includes Mercury, Venus, Earth, Mars, and the bodies in the asteroid belt . The outer Solar System includes Jupiter, Saturn, Uranus, Neptune, and
396-628: A decade of reliance on the Russians. In 2019, NASA announced the Artemis program , intending to return to the Moon and establish a permanent human presence. This was paired with the Artemis Accords with partner nations to establish rules of behavior and norms of space commercialization on the Moon. In 2023, NASA established the Moon to Mars Program office. The office is designed to oversee
528-662: A definite surface, as they are mainly composed of gases and liquids. Over 99.86% of the Solar System's mass is in the Sun and nearly 90% of the remaining mass is in Jupiter and Saturn. There is a strong consensus among astronomers that the Solar System has at least nine dwarf planets : Ceres , Orcus , Pluto , Haumea , Quaoar , Makemake , Gonggong , Eris , and Sedna . There are a vast number of small Solar System bodies , such as asteroids , comets , centaurs , meteoroids , and interplanetary dust clouds . Some of these bodies are in
660-408: A diameter of about 250 km (160 mi) and is one of the few minor planets possessing a ring system. Beyond the orbit of Neptune lies the area of the " trans-Neptunian region ", with the doughnut-shaped Kuiper belt, home of Pluto and several other dwarf planets, and an overlapping disc of scattered objects, which is tilted toward the plane of the Solar System and reaches much further out than
792-415: A few meters to hundreds of kilometers in size. Many asteroids are divided into asteroid groups and families based on their orbital characteristics. Some asteroids have natural satellites that orbit them , that is, asteroids that orbit larger asteroids. The asteroid belt occupies a torus-shaped region between 2.3 and 3.3 AU from the Sun, which lies between the orbits of Mars and Jupiter. It
924-469: A human in space, develop tracking and control systems, and identify other issues associated with human spaceflight. While much of NASA's attention turned to space, it did not put aside its aeronautics mission. Early aeronautics research attempted to build upon the X-1's supersonic flight to build an aircraft capable of hypersonic flight . The North American X-15 was a joint NASA–U.S. Air Force program, with
1056-583: A permanently manned space station and to do it within a decade. In 1985, NASA proposed the Space Station Freedom , which both the agency and President Reagan intended to be an international program. While this would add legitimacy to the program, there were concerns within NASA that the international component would dilute its authority within the project, having never been willing to work with domestic or international partners as true equals. There
1188-650: A possible source of antimatter at the center of the Milky Way and observing that the majority of gamma-ray bursts occur outside of the Milky Way galaxy. The Chandra X-ray Observatory was launched from the Columbia on STS-93 in 1999, observing black holes, quasars , supernova , and dark matter . It provided critical observations on the Sagittarius A* black hole at the center of the Milky Way galaxy and
1320-570: A relationship between these orbital distances, like the Titius–Bode law and Johannes Kepler's model based on the Platonic solids , but ongoing discoveries have invalidated these hypotheses. Some Solar System models attempt to convey the relative scales involved in the Solar System in human terms. Some are small in scale (and may be mechanical—called orreries )—whereas others extend across cities or regional areas. The largest such scale model,
1452-532: A shell surrounding the inert helium, and the energy output will be greater than at present. The outer layers of the Sun will expand to roughly 260 times its current diameter, and the Sun will become a red giant . Because of its increased surface area, the surface of the Sun will be cooler (2,600 K (4,220 °F) at its coolest) than it is on the main sequence. The expanding Sun is expected to vaporize Mercury as well as Venus, and render Earth and Mars uninhabitable (possibly destroying Earth as well). Eventually,
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#17327726668301584-413: A small fraction of the solar nebula, the terrestrial planets could not grow very large. The giant planets (Jupiter, Saturn, Uranus, and Neptune) formed further out, beyond the frost line, the point between the orbits of Mars and Jupiter where material is cool enough for volatile icy compounds to remain solid. The ices that formed these planets were more plentiful than the metals and silicates that formed
1716-540: A space station since the agency was created. In 1973, following the end of the Apollo lunar missions, NASA launched its first space station, Skylab , on the final launch of the Saturn V. Skylab reused a significant amount of Apollo and Saturn hardware, with a repurposed Saturn V third stage serving as the primary module for the space station. Damage to Skylab during its launch required spacewalks to be performed by
1848-417: Is 30 AU from the Sun. With a few exceptions, the farther a planet or belt is from the Sun, the larger the distance between its orbit and the orbit of the next nearest object to the Sun. For example, Venus is approximately 0.33 AU farther out from the Sun than Mercury, whereas Saturn is 4.3 AU out from Jupiter, and Neptune lies 10.5 AU out from Uranus. Attempts have been made to determine
1980-409: Is a great ring of debris similar to the asteroid belt, but consisting mainly of objects composed primarily of ice. It extends between 30 and 50 AU from the Sun. It is composed mainly of small Solar System bodies, although the largest few are probably large enough to be dwarf planets. There are estimated to be over 100,000 Kuiper belt objects with a diameter greater than 50 km (30 mi), but
2112-428: Is a small chance that another star will pass through the Solar System in the next few billion years. Although this could destabilize the system and eventually lead millions of years later to expulsion of planets, collisions of planets, or planets hitting the Sun, it would most likely leave the Solar System much as it is today. The Sun's main-sequence phase, from beginning to end, will last about 10 billion years for
2244-569: Is a typical star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core , releasing this energy from its outer photosphere . Astronomers classify it as a G-type main-sequence star . The largest objects that orbit the Sun are the eight planets . In order from the Sun, they are four terrestrial planets ( Mercury , Venus , Earth and Mars ); two gas giants ( Jupiter and Saturn ); and two ice giants ( Uranus and Neptune ). All terrestrial planets have solid surfaces. Inversely, all giant planets do not have
2376-412: Is no "gap" as seen between the size of Earth and of Neptune (with a radius 3.8 times as large). As many of these super-Earths are closer to their respective stars than Mercury is to the Sun, a hypothesis has arisen that all planetary systems start with many close-in planets, and that typically a sequence of their collisions causes consolidation of mass into few larger planets, but in case of the Solar System
2508-468: Is strong consensus among astronomers that five members of the Kuiper belt are dwarf planets . Many dwarf planet candidates are being considered, pending further data for verification. The scattered disc, which overlaps the Kuiper belt but extends out to near 500 AU, is thought to be the source of short-period comets. Scattered-disc objects are believed to have been perturbed into erratic orbits by
2640-430: Is the Solar System's star and by far its most massive component. Its large mass (332,900 Earth masses ), which comprises 99.86% of all the mass in the Solar System, produces temperatures and densities in its core high enough to sustain nuclear fusion of hydrogen into helium. This releases an enormous amount of energy , mostly radiated into space as electromagnetic radiation peaking in visible light . Because
2772-468: Is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter. The asteroid belt contains tens of thousands, possibly millions, of objects over one kilometer in diameter. Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth. The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident. Below are
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#17327726668302904-677: The Big Bang . The James Webb Space Telescope , named after the NASA administrator who lead the Apollo program, is an infrared observatory launched in 2021. The James Webb Space Telescope is a direct successor to the Hubble Space Telescope, intended to observe the formation of the first galaxies. Other space telescopes include the Kepler space telescope , launched in 2009 to identify planets orbiting extrasolar stars that may be Terran and possibly harbor life. The first exoplanet that
3036-836: The Decadal Surveys . " Science " marks these missions as primarily scientific in nature, under the Science Mission Directorate (SMD), as opposed to, e.g., human exploration missions under the Human Exploration and Operations Mission Directorate (HEOMD). The lines can be blurred, as when the Lunar Reconnaissance Orbiter began as a directed mission from the HEOMD, and was later transferred to the SMD. Flagship missions are not under
3168-797: The Environmental Science Services Administration on a series of weather satellites and the agency launched its experimental Applications Technology Satellites into geosynchronous orbit. NASA's first dedicated Earth observation satellite, Landsat , was launched in 1972. This led to NASA and the National Oceanic and Atmospheric Administration jointly developing the Geostationary Operational Environmental Satellite and discovering Ozone depletion . NASA had been pursuing spaceplane development since
3300-630: The Europa and observed that the moon may hold ice or liquid water. A joint NASA- European Space Agency - Italian Space Agency mission, Cassini–Huygens , was sent to Saturn 's moon Titan , which, along with Mars and Europa, are the only celestial bodies in the Solar System suspected of being capable of harboring life. Cassini discovered three new moons of Saturn and the Huygens probe entered Titan's atmosphere. The mission discovered evidence of liquid hydrocarbon lakes on Titan and subsurface water oceans on
3432-877: The International Space Station (ISS) along with the Commercial Crew Program , and oversees the development of the Orion spacecraft and the Space Launch System for the lunar Artemis program . NASA's science division is focused on better understanding Earth through the Earth Observing System ; advancing heliophysics through the efforts of the Science Mission Directorate 's Heliophysics Research Program; exploring bodies throughout
3564-784: The Johnson Space Center as the lead center for the design, development, and manufacturing of the Space Shuttle orbiter , while the Marshall Space Flight Center would lead the development of the launch system. NASA's series of lifting body aircraft, culminating in the joint NASA-U.S. Air Force Martin Marietta X-24 , directly informed the development of the Space Shuttle and future hypersonic flight aircraft. Official development of
3696-664: The Mars Global Surveyor orbiter and Mars Pathfinder , deploying the first Mars rover, Sojourner . During the early 2000s, the 2001 Mars Odyssey orbiter reached the planet and in 2004 the Sprit and Opportunity rovers landed on the Red Planet. This was followed in 2005 by the Mars Reconnaissance Orbiter and 2007 Phoenix Mars lander. The 2012 landing of Curiosity discovered that
3828-438: The Milky Way galaxy. The Solar System formed at least 4.568 billion years ago from the gravitational collapse of a region within a large molecular cloud . This initial cloud was likely several light-years across and probably birthed several stars. As is typical of molecular clouds, this one consisted mostly of hydrogen, with some helium, and small amounts of heavier elements fused by previous generations of stars. As
3960-555: The National Advisory Committee for Aeronautics (NACA) to give the U.S. space development effort a distinct civilian orientation, emphasizing peaceful applications in space science . It has since led most of America's space exploration programs, including Project Mercury , Project Gemini , the 1968–1972 Apollo Moon landing missions, the Skylab space station, and the Space Shuttle . Currently, NASA supports
4092-684: The National Advisory Committee for Aeronautics (NACA). Despite being the birthplace of aviation, by 1914 the United States recognized that it was far behind Europe in aviation capability. Determined to regain American leadership in aviation, the United States Congress created the Aviation Section of the U.S. Army Signal Corps in 1914 and established NACA in 1915 to foster aeronautical research and development. Over
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4224-565: The Orbiting Geophysical Observatory in the 1960s and 1970s to look down at Earth and observe its interactions with the Sun. The Uhuru satellite was the first dedicated x-ray telescope, mapping 85% of the sky and discovering a large number of black holes . Launched in the 1990s and early 2000s, the Great Observatories program are among NASA's most powerful telescopes. The Hubble Space Telescope
4356-658: The STS-1 mission, designed to serve as a flight test for the new spaceplane. NASA intended for the Space Shuttle to replace expendable launch systems like the Air Force's Atlas , Delta , and Titan and the European Space Agency 's Ariane . The Space Shuttle's Spacelab payload, developed by the European Space Agency, increased the scientific capabilities of shuttle missions over anything NASA
4488-635: The STS-60 mission in 1994 and the Discovery rendezvoused, but did not dock with, the Russian Mir in the STS-63 mission. This was followed by Atlantis' STS-71 mission where it accomplished the initial intended mission for the Space Shuttle, docking with a space station and transferring supplies and personnel. The Shuttle- Mir program would continue until 1998, when a series of orbital accidents on
4620-541: The Solar System with advanced robotic spacecraft such as New Horizons and planetary rovers such as Perseverance ; and researching astrophysics topics, such as the Big Bang , through the James Webb Space Telescope , the four Great Observatories , and associated programs. The Launch Services Program oversees launch operations for its uncrewed launches . NASA traces its roots to
4752-535: The Space Race when the Soviet Union gave up its lunar ambitions. As the first human to step on the surface of the Moon, Neil Armstrong uttered the now famous words: That's one small step for man, one giant leap for mankind. NASA would conduct six total lunar landings as part of the Apollo program, with Apollo 17 concluding the program in 1972. Wernher von Braun had advocated for NASA to develop
4884-620: The Space Shuttle began in 1972, with Rockwell International contracted to design the orbiter and engines, Martin Marietta for the external fuel tank , and Morton Thiokol for the solid rocket boosters . NASA acquired six orbiters: the Enterprise , Columbia , Challenger , Discovery , Atlantis , and Endeavour The Space Shuttle program also allowed NASA to make major changes to its Astronaut Corps . While almost all previous astronauts were Air Force or Naval test pilots,
5016-626: The Sweden Solar System , uses the 110-meter (361-foot) Avicii Arena in Stockholm as its substitute Sun, and, following the scale, Jupiter is a 7.5-meter (25-foot) sphere at Stockholm Arlanda Airport , 40 km (25 mi) away, whereas the farthest current object, Sedna , is a 10 cm (4 in) sphere in Luleå , 912 km (567 mi) away. At that scale, the distance to Proxima Centauri would be roughly 8 times further than
5148-453: The asteroid belt (between Mars's and Jupiter's orbit) and the Kuiper belt (just outside Neptune's orbit). Six planets, seven dwarf planets, and other bodies have orbiting natural satellites , which are commonly called 'moons'. The Solar System is constantly flooded by the Sun's charged particles , the solar wind , forming the heliosphere . Around 75–90 astronomical units from the Sun,
5280-498: The frost line , and it lies at roughly five times the Earth's distance from the Sun. The planets and other large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic . Smaller icy objects such as comets frequently orbit at significantly greater angles to this plane. Most of the planets in the Solar System have secondary systems of their own, being orbited by natural satellites called moons. All of
5412-419: The fusor stars in the Milky Way . The Sun is a population I star , having formed in the spiral arms of the Milky Way galaxy. It has a higher abundance of elements heavier than hydrogen and helium (" metals " in astronomical parlance) than the older population II stars in the galactic bulge and halo . Elements heavier than hydrogen and helium were formed in the cores of ancient and exploding stars, so
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5544-538: The grand tack hypothesis suggests that a final inward migration of Jupiter dispersed much of the asteroid belt, leading to the Late Heavy Bombardment of the inner planets. The Solar System remains in a relatively stable, slowly evolving state by following isolated, gravitationally bound orbits around the Sun. Although the Solar System has been fairly stable for billions of years, it is technically chaotic , and may eventually be disrupted . There
5676-427: The heliosphere , which spans much of the Solar System. Along with light , the Sun radiates a continuous stream of charged particles (a plasma ) called the solar wind . This stream spreads outwards at speeds from 900,000 kilometres per hour (560,000 mph) to 2,880,000 kilometres per hour (1,790,000 mph), filling the vacuum between the bodies of the Solar System. The result is a thin , dusty atmosphere, called
5808-405: The inner planets . Despite these successes, Congress was unwilling to fund further interplanetary missions and NASA Administrator James Webb suspended all future interplanetary probes to focus resources on the Apollo program. Following the conclusion of the Apollo program, NASA resumed launching interplanetary probes and expanded its space science program. The first planet tagged for exploration
5940-554: The interplanetary medium , which extends to at least 100 AU . Activity on the Sun's surface, such as solar flares and coronal mass ejections , disturbs the heliosphere, creating space weather and causing geomagnetic storms . Coronal mass ejections and similar events blow a magnetic field and huge quantities of material from the surface of the Sun. The interaction of this magnetic field and material with Earth's magnetic field funnels charged particles into Earth's upper atmosphere, where its interactions create aurorae seen near
6072-421: The magnetic poles . The largest stable structure within the heliosphere is the heliospheric current sheet , a spiral form created by the actions of the Sun's rotating magnetic field on the interplanetary medium. The inner Solar System is the region comprising the terrestrial planets and the asteroids . Composed mainly of silicates and metals, the objects of the inner Solar System are relatively close to
6204-566: The pre-solar nebula collapsed, conservation of angular momentum caused it to rotate faster. The center, where most of the mass collected, became increasingly hotter than the surroundings. As the contracting nebula spun faster, it began to flatten into a protoplanetary disc with a diameter of roughly 200 AU and a hot, dense protostar at the center. The planets formed by accretion from this disc, in which dust and gas gravitationally attracted each other, coalescing to form ever larger bodies. Hundreds of protoplanets may have existed in
6336-420: The 1950s as a response to Soviet lunar exploration, however most missions ended in failure. The Lunar Orbiter program had greater success, mapping the surface in preparation for Apollo landings and measured Selenography , conducted meteoroid detection, and measured radiation levels. The Surveyor program conducted uncrewed lunar landings and takeoffs, as well as taking surface and regolith observations. Despite
6468-472: The 1960s, blending the administration's dual aeronautics and space missions. NASA viewed a spaceplane as part of a larger program, providing routine and economical logistical support to a space station in Earth orbit that would be used as a hub for lunar and Mars missions. A reusable launch vehicle would then have ended the need for expensive and expendable boosters like the Saturn V . In 1969, NASA designated
6600-679: The 44 commercial companies that contracted with NASA to deploy their satellites to return to expendable launch vehicles. When the Space Shuttle returned to flight with the STS-26 mission, it had undergone significant modifications to improve its reliability and safety. Following the collapse of the Soviet Union, the Russian Federation and United States initiated the Shuttle- Mir program . The first Russian cosmonaut flew on
6732-520: The Army's Project Adam, served as the foundation for Project Mercury . NASA established the Space Task Group to manage the program, which would conduct crewed sub-orbital flights with the Army's Redstone rockets and orbital flights with the Air Force's Atlas launch vehicles. While NASA intended for its first astronauts to be civilians, President Eisenhower directed that they be selected from
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#17327726668306864-574: The Keplar space telescope confirmed was Kepler-22b , orbiting within the habitable zone of its star. NASA also launched a number of different satellites to study Earth, such as Television Infrared Observation Satellite (TIROS) in 1960, which was the first weather satellite. NASA and the United States Weather Bureau cooperated on future TIROS and the second generation Nimbus program of weather satellites. It also worked with
6996-470: The Kuiper belt. The entire region is still largely unexplored . It appears to consist overwhelmingly of many thousands of small worlds—the largest having a diameter only a fifth that of Earth and a mass far smaller than that of the Moon—composed mainly of rock and ice. This region is sometimes described as the "third zone of the Solar System", enclosing the inner and the outer Solar System. The Kuiper belt
7128-558: The Martian interior. The 2021 Perseverance rover carried the first extraplanetary aircraft, a helicopter named Ingenuity . NASA also launched missions to Mercury in 2004, with the MESSENGER probe demonstrating as the first use of a solar sail . NASA also launched probes to the outer Solar System starting in the 1960s. Pioneer 10 was the first probe to the outer planets, flying by Jupiter , while Pioneer 11 provided
7260-483: The Moon and going to Mars. Embracing this approach, NASA's Commercial Crew Program started by contracting cargo delivery to the International Space Station and flew its first operational contracted mission on SpaceX Crew-1 . This marked the first time since the retirement of the Space Shuttle that NASA was able to launch its own astronauts on an American spacecraft from the United States, ending
7392-510: The Moon is from Earth. If the Sun–Neptune distance is scaled to 100 metres (330 ft), then the Sun would be about 3 cm (1.2 in) in diameter (roughly two-thirds the diameter of a golf ball), the giant planets would be all smaller than about 3 mm (0.12 in), and Earth's diameter along with that of the other terrestrial planets would be smaller than a flea (0.3 mm or 0.012 in) at this scale. Besides solar energy,
7524-659: The Naval Research Laboratory's Project Vanguard, the Army's Jet Propulsion Laboratory (JPL), and the Army Ballistic Missile Agency under Wernher von Braun . This left NASA firmly as the United States' civil space lead and the Air Force as the military space lead. Plans for human spaceflight began in the U.S. Armed Forces prior to NASA's creation. The Air Force's Man in Space Soonest project formed in 1956, coupled with
7656-730: The Pilotless Aircraft Research Division. The Soviet Union's launch of Sputnik 1 ushered in the Space Age and kicked off the Space Race . Despite NACA's early rocketry program, the responsibility for launching the first American satellite fell to the Naval Research Laboratory 's Project Vanguard , whose operational issues ensured the Army Ballistic Missile Agency would launch Explorer 1 , America's first satellite, on February 1, 1958. The Eisenhower Administration decided to split
7788-557: The Russians be included. In 1993, the Clinton Administration announced that the Space Station Freedom would become the International Space Station in an agreement with the Russian Federation. This allowed the Russians to maintain their space program through an infusion of American currency to maintain their status as one of the two premier space programs. While the United States built and launched
7920-507: The Russians to fly to the International Space Station for four days, despite the opposition of NASA to the idea. Advocates of this new commercial approach for NASA included former astronaut Buzz Aldrin , who remarked that it would return NASA to its roots as a research and development agency, with commercial entities actually operating the space systems. Having corporations take over orbital operations would also allow NASA to focus all its efforts on deep space exploration and returning humans to
8052-462: The Solar System is a measure of the total amount of orbital and rotational momentum possessed by all its moving components. Although the Sun dominates the system by mass, it accounts for only about 2% of the angular momentum. The planets, dominated by Jupiter, account for most of the rest of the angular momentum due to the combination of their mass, orbit, and distance from the Sun, with a possibly significant contribution from comets. The radius of
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#17327726668308184-545: The Solar System is home to the giant planets and their large moons. The centaurs and many short-period comets orbit in this region. Due to their greater distance from the Sun, the solid objects in the outer Solar System contain a higher proportion of volatiles such as water, ammonia, and methane, than planets of the inner Solar System because their lower temperatures allow these compounds to remain solid, without significant sublimation . The four outer planets, called giant planets or Jovian planets, collectively make up 99% of
8316-457: The Solar System stands out in lacking planets interior to the orbit of Mercury. The known Solar System lacks super-Earths , planets between one and ten times as massive as the Earth, although the hypothetical Planet Nine , if it does exist, could be a super-Earth orbiting in the edge of the Solar System. Uncommonly, it has only small terrestrial and large gas giants; elsewhere planets of intermediate size are typical—both rocky and gas—so there
8448-400: The Solar System, created by heat and light pressure from the early Sun; those objects closer to the Sun, which are more affected by heat and light pressure, are composed of elements with high melting points. Objects farther from the Sun are composed largely of materials with lower melting points. The boundary in the Solar System beyond which those volatile substances could coalesce is known as
8580-422: The Solar System. Mars has long been a planet of intense fascination for NASA, being suspected of potentially having harbored life. Mariner 5 was the first NASA spacecraft to flyby Mars, followed by Mariner 6 and Mariner 7 . Mariner 9 was the first orbital mission to Mars. Launched in 1975, Viking program consisted of two landings on Mars in 1976. Follow-on missions would not be launched until 1996, with
8712-633: The Space Shuttle Columbia disaster in 2003, NASA was forced to rely on Russian Soyuz launches for its astronauts and the 2011 retirement of the Space Shuttle accelerated the station's completion. In the 1980s, right after the first flight of the Space Shuttle, NASA started a joint program with the Department of Defense to develop the Rockwell X-30 National Aerospace Plane. NASA realized that
8844-418: The Space Shuttle allowed NASA to begin recruiting more non-military scientific and technical experts. A prime example is Sally Ride , who became the first American woman to fly in space on STS-7 . This new astronaut selection process also allowed NASA to accept exchange astronauts from U.S. allies and partners for the first time. The first Space Shuttle flight occurred in 1981, when the Columbia launched on
8976-443: The Space Shuttle and expand space exploration beyond low Earth orbit. Constellation was intended to use a significant amount of former Space Shuttle equipment and return astronauts to the Moon. This program was canceled by the Obama Administration . Former astronauts Neil Armstrong , Gene Cernan , and Jim Lovell sent a letter to President Barack Obama to warn him that if the United States did not get new human spaceflight ability,
9108-478: The Space Shuttle began flying, selling it as an orbital laboratory, repair station, and a jumping off point for lunar and Mars missions. NASA found a strong advocate in President Ronald Reagan , who declared in a 1984 speech: America has always been greatest when we dared to be great. We can reach for greatness again. We can follow our dreams to distant stars, living and working in space for peaceful, economic, and scientific gain. Tonight I am directing NASA to develop
9240-444: The Space Shuttle, while a massive technological accomplishment, would not be able to live up to all its promises. Designed to be a single-stage-to-orbit spaceplane, the X-30 had both civil and military applications. With the end of the Cold War , the X-30 was canceled in 1992 before reaching flight status. Following the Space Shuttle Columbia disaster in 2003, President Bush started the Constellation program to smoothly replace
9372-483: The Space Shuttle. Due to technical challenges, the spacecraft was cancelled in 2001. Despite this, it was the first time a commercial space company directly expended a significant amount of its resources into spacecraft development. The advent of space tourism also forced NASA to challenge its assumption that only governments would have people in space. The first space tourist was Dennis Tito , an American investment manager and former aerospace engineer who contracted with
9504-507: The Space Station Freedom was controversial, with much of the debate centering on cost. Several redesigns to reduce cost were conducted in the early 1990s, stripping away much of its functions. Despite calls for Congress to terminate the program, it continued, in large part because by 1992 it had created 75,000 jobs across 39 states. By 1993, President Bill Clinton attempted to significantly reduce NASA's budget and directed costs be significantly reduced, aerospace industry jobs were not lost, and
9636-406: The Sun by the outer planets, and are expected to become comets or be ejected out of the Solar System. While most centaurs are inactive and asteroid-like, some exhibit cometary activity, such as the first centaur discovered, 2060 Chiron , which has been classified as a comet (95P) because it develops a coma just as comets do when they approach the Sun. The largest known centaur, 10199 Chariklo , has
9768-455: The Sun compared to around two billion years for all other subsequent phases of the Sun's pre- remnant life combined. The Solar System will remain roughly as it is known today until the hydrogen in the core of the Sun has been entirely converted to helium, which will occur roughly 5 billion years from now. This will mark the end of the Sun's main-sequence life. At that time, the core of the Sun will contract with hydrogen fusion occurring along
9900-495: The Sun fuses hydrogen at its core, it is a main-sequence star. More specifically, it is a G2-type main-sequence star , where the type designation refers to its effective temperature . Hotter main-sequence stars are more luminous but shorter lived. The Sun's temperature is intermediate between that of the hottest stars and that of the coolest stars. Stars brighter and hotter than the Sun are rare, whereas substantially dimmer and cooler stars, known as red dwarfs , make up about 75% of
10032-422: The Sun is 0.0047 AU (700,000 km; 400,000 mi). Thus, the Sun occupies 0.00001% (1 part in 10 ) of the volume of a sphere with a radius the size of Earth's orbit, whereas Earth's volume is roughly 1 millionth (10 ) that of the Sun. Jupiter, the largest planet, is 5.2 AU from the Sun and has a radius of 71,000 km (0.00047 AU; 44,000 mi), whereas the most distant planet, Neptune,
10164-403: The Sun is growing brighter; early in its main-sequence life its brightness was 70% that of what it is today. The temperature, reaction rate , pressure, and density increased until hydrostatic equilibrium was achieved: the thermal pressure counterbalancing the force of gravity. At this point, the Sun became a main-sequence star. Solar wind from the Sun created the heliosphere and swept away
10296-472: The Sun twice for every three times that Neptune does, or once for every two. The classical belt consists of objects having no resonance with Neptune, and extends from roughly 39.4 to 47.7 AU. Members of the classical Kuiper belt are sometimes called "cubewanos", after the first of their kind to be discovered, originally designated 1992 QB 1 , (and has since been named Albion); they are still in near primordial, low-eccentricity orbits. Currently, there
10428-499: The Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn. This region is within the frost line , which is a little less than 5 AU from the Sun. The four terrestrial or inner planets have dense, rocky compositions, few or no moons , and no ring systems . They are composed largely of refractory minerals such as silicates —which form their crusts and mantles —and metals such as iron and nickel which form their cores . Three of
10560-602: The U.S. risked become a second or third-rate space power. As early as the Reagan Administration, there had been calls for NASA to expand private sector involvement in space exploration rather than do it all in-house. In the 1990s, NASA and Lockheed Martin entered into an agreement to develop the Lockheed Martin X-33 demonstrator of the VentureStar spaceplane, which was intended to replace
10692-678: The United States' military and civil spaceflight programs, which were organized together under the Defense Department 's Advanced Research Projects Agency . NASA was established on July 29, 1958, with the signing of the National Aeronautics and Space Act and it began operations on October 1, 1958. As the US's premier aeronautics agency, NACA formed the core of NASA's new structure by reassigning 8,000 employees and three major research laboratories. NASA also proceeded to absorb
10824-565: The astronomical sense (chemical compounds with melting points of up to a few hundred kelvins such as water, methane, ammonia, hydrogen sulfide , and carbon dioxide . ) Icy substances comprise the majority of the satellites of the giant planets and small objects that lie beyond Neptune's orbit. The centaurs are icy, comet-like bodies whose semi-major axes are longer than Jupiter's and shorter than Neptune's (between 5.5 and 30 AU). These are former Kuiper belt and scattered disc objects (SDOs) that were gravitationally perturbed closer to
10956-402: The bodies in the Kuiper belt . Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune . The principal component of the Solar System is the Sun, a G-type main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally. The Sun's four largest orbiting bodies,
11088-686: The budget of each mission, typically the most expensive mission in the scientific discipline. Within the Astrophysics Division and the Planetary Science Division, the large strategic missions are usually in excess of US$ 1 billion. Within Earth Science Division and Heliophysics Division, the large strategic missions are usually in excess of US$ 500 million. "Strategic" refers to their role advancing multiple strategic priorities set forth in plans such as
11220-410: The collisions caused their destruction and ejection. The orbits of Solar System planets are nearly circular. Compared to many other systems, they have smaller orbital eccentricity . Although there are attempts to explain it partly with a bias in the radial-velocity detection method and partly with long interactions of a quite high number of planets, the exact causes remain undetermined. The Sun
11352-432: The core will be hot enough for helium fusion; the Sun will burn helium for a fraction of the time it burned hydrogen in the core. The Sun is not massive enough to commence the fusion of heavier elements, and nuclear reactions in the core will dwindle. Its outer layers will be ejected into space, leaving behind a dense white dwarf , half the original mass of the Sun but only the size of Earth. The ejected outer layers may form
11484-413: The descriptions of the three largest bodies in the asteroid belt. They are all considered to be relatively intact protoplanets , a precursor stage before becoming a fully-formed planet (see List of exceptional asteroids ): Hilda asteroids are in a 3:2 resonance with Jupiter; that is, they go around the Sun three times for every two Jovian orbits. They lie in three linked clusters between Jupiter and
11616-441: The early Solar System, but they either merged or were destroyed or ejected, leaving the planets, dwarf planets, and leftover minor bodies . Due to their higher boiling points, only metals and silicates could exist in solid form in the warm inner Solar System close to the Sun (within the frost line ). They would eventually form the rocky planets of Mercury, Venus, Earth, and Mars. Because these refractory materials only comprised
11748-574: The end of the 1960s and installed James E. Webb as NASA administrator to achieve this goal. On May 25, 1961, President Kennedy openly declared this goal in his "Urgent National Needs" speech to the United States Congress, declaring: I believe this Nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to Earth. No single space project in this period will be more impressive to mankind, or more important for
11880-420: The first close up view of the planet. Both probes became the first objects to leave the Solar System. The Voyager program launched in 1977, conducting flybys of Jupiter and Saturn , Neptune , and Uranus on a trajectory to leave the Solar System. The Galileo spacecraft, deployed from the Space Shuttle flight STS-34 , was the first spacecraft to orbit Jupiter, discovering evidence of subsurface oceans on
12012-515: The first crew to make it habitable and operational. Skylab hosted nine missions and was decommissioned in 1974 and deorbited in 1979, two years prior to the first launch of the Space Shuttle and any possibility of boosting its orbit. In 1975, the Apollo–Soyuz mission was the first ever international spaceflight and a major diplomatic accomplishment between the Cold War rivals, which also marked
12144-453: The first generation of stars had to die before the universe could be enriched with these atoms. The oldest stars contain few metals, whereas stars born later have more. This higher metallicity is thought to have been crucial to the Sun's development of a planetary system because the planets formed from the accretion of "metals". The region of space dominated by the Solar magnetosphere is
12276-402: The first humans to see the Earth as a globe in space, the first to witness an Earthrise , and the first to see and manually photograph the far side of the Moon. The first lunar landing was conducted by Apollo 11. Commanded by Neil Armstrong with astronauts Buzz Aldrin and Michael Collins , Apollo 11 was one of the most significant missions in NASA's history, marking the end of
12408-559: The four Great Observatories , only the Spitzer Space Telescope is not a Flagship mission. Initially budgeted at US$ 2 billion, Spitzer was downscoped to a medium-size mission of US$ 720 million. NASA The National Aeronautics and Space Administration ( NASA / ˈ n æ s ə / ) is an independent agency of the U.S. federal government responsible for the civil space program , aeronautics research, and space research. Established in 1958 , it succeeded
12540-407: The four inner planets (Venus, Earth, and Mars) have atmospheres substantial enough to generate weather; all have impact craters and tectonic surface features, such as rift valleys and volcanoes. Asteroids except for the largest, Ceres, are classified as small Solar System bodies and are composed mainly of carbonaceous , refractory rocky and metallic minerals, with some ice. They range from
12672-441: The giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System (including the four terrestrial planets, the dwarf planets, moons, asteroids , and comets) together comprise less than 0.002% of the Solar System's total mass. The Sun is composed of roughly 98% hydrogen and helium, as are Jupiter and Saturn. A composition gradient exists in
12804-569: The gravitational influence of Neptune's early outward migration . Most scattered disc objects have perihelia within the Kuiper belt but aphelia far beyond it (some more than 150 AU from the Sun). SDOs' orbits can be inclined up to 46.8° from the ecliptic plane. Some astronomers consider the scattered disc to be merely another region of the Kuiper belt and describe scattered-disc objects as "scattered Kuiper belt objects". Some astronomers classify centaurs as inward-scattered Kuiper belt objects along with
12936-488: The hypersonic test aircraft becoming the first non-dedicated spacecraft to cross from the atmosphere to outer space. The X-15 also served as a testbed for Apollo program technologies, as well as ramjet and scramjet propulsion. Escalations in the Cold War between the United States and Soviet Union prompted President John F. Kennedy to charge NASA with landing an American on the Moon and returning him safely to Earth by
13068-415: The larger moons orbit their planets in prograde direction, matching the direction of planetary rotation; Neptune's moon Triton is the largest to orbit in the opposite, retrograde manner. Most larger objects rotate around their own axes in the prograde direction relative to their orbit, though the rotation of Venus is retrograde. To a good first approximation, Kepler's laws of planetary motion describe
13200-491: The largest natural satellites are in synchronous rotation , with one face permanently turned toward their parent. The four giant planets have planetary rings, thin discs of tiny particles that orbit them in unison. As a result of the formation of the Solar System , planets and most other objects orbit the Sun in the same direction that the Sun is rotating. That is, counter-clockwise, as viewed from above Earth's north pole. There are exceptions, such as Halley's Comet . Most of
13332-451: The last flight of the Apollo capsule. Flown in 1975, a U.S. Apollo spacecraft docked with a Soviet Soyuz capsule. During the 1960s, NASA started its space science and interplanetary probe program. The Mariner program was its flagship program, launching probes to Venus , Mars , and Mercury in the 1960s. The Jet Propulsion Laboratory was the lead NASA center for robotic interplanetary exploration, making significant discoveries about
13464-422: The level of cosmic-ray penetration in the Solar System varies, though by how much is unknown. The zone of habitability of the Solar System is conventionally located in the inner Solar System, where planetary surface or atmospheric temperatures admit the possibility of liquid water . Habitability might be possible in subsurface oceans of various outer Solar System moons. Compared to many extrasolar systems,
13596-484: The long-range exploration of space; and none will be so difficult or expensive to accomplish. Kennedy gave his " We choose to go to the Moon " speech the next year, on September 12, 1962 at Rice University , where he addressed the nation hoping to reinforce public support for the Apollo program. Despite attacks on the goal of landing astronauts on the Moon from the former president Dwight Eisenhower and 1964 presidential candidate Barry Goldwater , President Kennedy
13728-443: The main asteroid belt. Trojans are bodies located within another body's gravitationally stable Lagrange points : L 4 , 60° ahead in its orbit, or L 5 , 60° behind in its orbit. Every planet except Mercury and Saturn is known to possess at least 1 trojan. The Jupiter trojan population is roughly equal to that of the asteroid belt. After Jupiter, Neptune possesses the most confirmed trojans, at 28. The outer region of
13860-434: The majority of the International Space Station, Russia, Canada, Japan, and the European Space Agency all contributed components. Despite NASA's insistence that costs would be kept at a budget of $ 17.4, they kept rising and NASA had to transfer funds from other programs to keep the International Space Station solvent. Ultimately, the total cost of the station was $ 150 billion, with the United States paying for two-thirds.Following
13992-400: The mass orbiting the Sun. All four giant planets have multiple moons and a ring system, although only Saturn's rings are easily observed from Earth. Jupiter and Saturn are composed mainly of gases with extremely low melting points, such as hydrogen, helium, and neon , hence their designation as gas giants . Uranus and Neptune are ice giants , meaning they are largely composed of 'ice' in
14124-556: The military. The Mercury 7 astronauts included three Air Force pilots, three Navy aviators, and one Marine Corps pilot. On May 5, 1961, Alan Shepard became the first American to enter space, performing a suborbital spaceflight in the Freedom 7 . This flight occurred less than a month after the Soviet Yuri Gagarin became the first human in space, executing a full orbital spaceflight. NASA's first orbital spaceflight
14256-634: The moon of Enceladus , which could harbor life. Finally launched in 2006, the New Horizons mission was the first spacecraft to visit Pluto and the Kuiper Belt . Beyond interplanetary probes, NASA has launched many space telescopes . Launched in the 1960s, the Orbiting Astronomical Observatory were NASA's first orbital telescopes, providing ultraviolet, gamma-ray, x-ray, and infrared observations. NASA launched
14388-476: The next forty years, NACA would conduct aeronautical research in support of the U.S. Air Force , U.S. Army , U.S. Navy , and the civil aviation sector. After the end of World War II , NACA became interested in the possibilities of guided missiles and supersonic aircraft, developing and testing the Bell X-1 in a joint program with the U.S. Air Force . NACA's interest in space grew out of its rocketry program at
14520-402: The orbits of objects around the Sun. These laws stipulate that each object travels along an ellipse with the Sun at one focus , which causes the body's distance from the Sun to vary over the course of its year. A body's closest approach to the Sun is called its perihelion , whereas its most distant point from the Sun is called its aphelion . With the exception of Mercury, the orbits of
14652-464: The planets are nearly circular, but many comets, asteroids, and Kuiper belt objects follow highly elliptical orbits. Kepler's laws only account for the influence of the Sun's gravity upon an orbiting body, not the gravitational pulls of different bodies upon each other. On a human time scale, these perturbations can be accounted for using numerical models , but the planetary system can change chaotically over billions of years. The angular momentum of
14784-415: The primary characteristic of the Solar System enabling the presence of life is the heliosphere and planetary magnetic fields (for those planets that have them). These magnetic fields partially shield the Solar System from high-energy interstellar particles called cosmic rays . The density of cosmic rays in the interstellar medium and the strength of the Sun's magnetic field change on very long timescales, so
14916-740: The purview of any larger "Flagship Program", unlike, e.g., Discovery-class missions that are under the purview of the Discovery Program . Unlike these competed classes that tender proposals through a competitive selection process, the development of Flagship missions is directed to a specific institution — usually a NASA center or the Jet Propulsion Laboratory — by the Science Mission Directorate . Flagship missions are developed ad-hoc, with no predetermined launch cadence or uniform budget size. Flagship missions are always Class A missions: high priority, very low risk. Of
15048-570: The radiation levels on Mars were equal to those on the International Space Station , greatly increasing the possibility of Human exploration, and observed the key chemical ingredients for life to occur. In 2013, the Mars Atmosphere and Volatile Evolution ( MAVEN ) mission observed the Martian upper atmosphere and space environment and in 2018, the Interior exploration using Seismic Investigations Geodesy, and Heat Transport ( InSight ) studied
15180-511: The remaining gas and dust from the protoplanetary disc into interstellar space. Following the dissipation of the protoplanetary disk , the Nice model proposes that gravitational encounters between planetisimals and the gas giants caused each to migrate into different orbits. This led to dynamical instability of the entire system, which scattered the planetisimals and ultimately placed the gas giants in their current positions. During this period,
15312-507: The satellites were repaired and relaunched. Despite ushering in a new era of spaceflight, where NASA was contracting launch services to commercial companies, the Space Shuttle was criticized for not being as reusable and cost-effective as advertised. In 1986, Challenger disaster on the STS-51L mission resulted in the loss of the spacecraft and all seven astronauts on launch, grounding the entire space shuttle fleet for 36 months and forced
15444-676: The separation of dark and regular matter during galactic collisions. Finally, the Spitzer Space Telescope is an infrared telescope launched in 2003 from a Delta II rocket. It is in a trailing orbit around the Sun, following the Earth and discovered the existence of brown dwarf stars . Other telescopes, such as the Cosmic Background Explorer and the Wilkinson Microwave Anisotropy Probe , provided evidence to support
15576-560: The setback caused by the Apollo 1 fire, which killed three astronauts, the program proceeded. Apollo 8 was the first crewed spacecraft to leave low Earth orbit and the first human spaceflight to reach the Moon . The crew orbited the Moon ten times on December 24 and 25, 1968, and then traveled safely back to Earth . The three Apollo 8 astronauts— Frank Borman , James Lovell , and William Anders —were
15708-404: The solar wind is halted, resulting in the heliopause . This is the boundary of the Solar System to interstellar space . The outermost region of the Solar System is the theorized Oort cloud , the source for long-period comets , extending to a radius of 2,000–200,000 AU . The closest star to the Solar System, Proxima Centauri , is 4.25 light-years (269,000 AU) away. Both stars belong to
15840-592: The space agency where he would serve as the director of the Apollo program. Development of the Saturn V rocket was led by Wernher von Braun and his team at the Marshall Space Flight Center , derived from the Army Ballistic Missile Agency's original Saturn I . The Apollo spacecraft was designed and built by North American Aviation , while the Apollo Lunar Module was designed and built by Grumman . To develop
15972-549: The space shuttle be retired. In 2006, the Space Shuttle returned to flight, conducting several mission to service the Hubble Space Telescope , but was retired following the STS-135 resupply mission to the International Space Station in 2011. NASA never gave up on the idea of a space station after Skylab's reentry in 1979. The agency began lobbying politicians to support building a larger space station as soon as
16104-481: The space station spelled an end to the program. In 2003, a second space shuttle was destroyed when the Columbia was destroyed upon reentry during the STS-107 mission, resulting in the loss of the spacecraft and all seven astronauts. This accident marked the beginning of the retiring of the Space Shuttle program, with President George W. Bush directing that upon the completion of the International Space Station,
16236-466: The spaceflight skills and equipment required for a lunar mission, NASA initiated Project Gemini . Using a modified Air Force Titan II launch vehicle, the Gemini capsule could hold two astronauts for flights of over two weeks. Gemini pioneered the use of fuel cells instead of batteries, and conducted the first American spacewalks and rendezvous operations . The Ranger Program was started in
16368-480: The terrestrial inner planets, allowing them to grow massive enough to capture large atmospheres of hydrogen and helium, the lightest and most abundant elements. Leftover debris that never became planets congregated in regions such as the asteroid belt, Kuiper belt, and Oort cloud. Within 50 million years, the pressure and density of hydrogen in the center of the protostar became great enough for it to begin thermonuclear fusion . As helium accumulates at its core,
16500-456: The total mass of the Kuiper belt is thought to be only a tenth or even a hundredth the mass of Earth. Many Kuiper belt objects have satellites, and most have orbits that are substantially inclined (~10°) to the plane of the ecliptic. The Kuiper belt can be roughly divided into the " classical " belt and the resonant trans-Neptunian objects . The latter have orbits whose periods are in a simple ratio to that of Neptune: for example, going around
16632-450: The various projects, mission architectures and associated timelines relevant to lunar and Mars exploration and science. Solar System The Solar System is the gravitationally bound system of the Sun and the objects that orbit it. It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc . The Sun
16764-461: Was Venus , sharing many similar characteristics to Earth. First visited by American Mariner 2 spacecraft, Venus was observed to be a hot and inhospitable planet. Follow-on missions included the Pioneer Venus project in the 1970s and Magellan , which performed radar mapping of Venus' surface in the 1980s and 1990s. Future missions were flybys of Venus, on their way to other destinations in
16896-683: Was able to previously accomplish. NASA launched its first commercial satellites on the STS-5 mission and in 1984, the STS-41-C mission conducted the world's first on-orbit satellite servicing mission when the Challenger captured and repaired the malfunctioning Solar Maximum Mission satellite. It also had the capability to return malfunctioning satellite to Earth, like it did with the Palapa B2 and Westar 6 satellites. Once returned to Earth,
17028-424: Was able to protect NASA's growing budget, of which 50% went directly to human spaceflight and it was later estimated that, at its height, 5% of Americans worked on some aspect of the Apollo program. Mirroring the Department of Defense's program management concept using redundant systems in building the first intercontinental ballistic missiles, NASA requested the Air Force assign Major General Samuel C. Phillips to
17160-472: Was also a concern with sharing sensitive space technologies with the Europeans, which had the potential to dilute America's technical lead. Ultimately, an international agreement to develop the Space Station Freedom program would be signed with thirteen countries in 1985, including the European Space Agency member states, Canada , and Japan . Despite its status as the first international space program,
17292-601: Was conducted by John Glenn on February 20, 1962, in the Friendship 7 , making three full orbits before reentering. Glenn had to fly parts of his final two orbits manually due to an autopilot malfunction. The sixth and final Mercury mission was flown by Gordon Cooper in May 1963, performing 22 orbits over 34 hours in the Faith 7 . The Mercury Program was wildly recognized as a resounding success, achieving its objectives to orbit
17424-497: Was launched in 1990 on STS-31 from the Discovery and could view galaxies 15 billion light years away. A major defect in the telescope's mirror could have crippled the program, had NASA not used computer enhancement to compensate for the imperfection and launched five Space Shuttle servicing flights to replace the damaged components. The Compton Gamma Ray Observatory was launched from the Atlantis on STS-37 in 1991, discovering
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