93-421: The Discovery Program is a series of Solar System exploration missions funded by the U.S. National Aeronautics and Space Administration (NASA) through its Planetary Missions Program Office . The cost of each mission is capped at a lower level than missions from NASA's New Frontiers or Flagship Programs. As a result, Discovery missions tend to be more focused on a specific scientific goal rather than serving
186-632: A spherical Earth , which they refer to as bhugol (or भूगोल in Hindi and Sanskrit), which literally translates to "spherical land". Ancient models were typically geocentric , putting the Earth at the center of the universe, based solely in the common experience of seeing the skies slowly moving around above our heads, and by feeling the land under our feet to be firmly at rest. Some traditions in Chinese cosmology proposed an outer surface to which planets and
279-450: A transit of Mercury across the Sun, leading him to realise that observations of the solar parallax of a planet (more ideally using the transit of Venus ) could be used to trigonometrically determine the distances between Earth, Venus , and the Sun. In 1705, Halley realised that repeated sightings of a comet were recording the same object, returning regularly once every 75–76 years. This
372-551: A volume-equivalent diameter of approximately 16.8 kilometers (10.4 miles). Visited by the NEAR Shoemaker space probe in 1998, it became the first asteroid ever studied from its own orbit. The asteroid was discovered by German astronomer C. G. Witt at the Berlin Observatory on 13 August 1898 in an eccentric orbit between Mars and Earth. It was later named after Eros , a god from Greek mythology ,
465-574: A Venus orbiter mission. A previous proposal of Vesper had also been a finalist in the 1998 round of selection. The three finalists were announced in October 2006 and awarded US$ 1.2 million to further develop their proposals for the final round. In November 2007 NASA selected the GRAIL mission as the next Discovery mission, with a goal of mapping lunar gravity and a 2011 launch. There were 23 other proposals that were also under consideration. The mission had
558-560: A body in heliocentric conjunction with Earth, its retrograde motion is very small. For example, in January and February 2137, it moves retrograde only 34 minutes in right ascension. In the novel and television series The Expanse , a catastrophic science experiment is unleashed on a civilian population living within tunnels cut through Eros. This so-called "Eros Incident" ends with the asteroid mysteriously breaking its usual orbit and crashing into Venus . It makes an appearance in
651-530: A budget of US$ 375 million (then-year dollars) which included construction and launch. The Announcement of Opportunity for a Discovery mission released on June 7, 2010. For this cycle, 28 proposals were received; 3 were for the Moon, 4 for Mars, 7 for Venus, 1 for Jupiter, 1 to a Jupiter Trojan, 2 to Saturn, 7 to asteroids, and 3 to comets. Out of the 28 proposals, three finalists received US$ 3 million in May 2011 to develop
744-598: A comet sample-return mission, was selected in November 1995 over the two other finalists. In October 1997, NASA selected Genesis and CONTOUR as the next Discovery missions, out of 34 proposals that were submitted in December 1996. The five finalists were: In July 1999, NASA selected MESSENGER and Deep Impact as the next Discovery Program missions. MESSENGER was the first Mercury orbiter and mission to that planet since Mariner 10 . Both missions targeted
837-551: A concept Phase A study was JASSI, which was a Jupiter flyby mission based on the New Frontiers Mission Juno that was already under consideration for final selection (eventually Juno was selected as the 2nd New Frontiers mission in 2005 and launched in 2011). No other discovery mission proposed in response to the Announcement of Opportunity was considered for concept study and therefore no Discovery mission
930-593: A detailed concept study: In August 2012, InSight was selected for development and launch. The mission launched on May 5, 2018, and successfully landed on Mars on November 26. In February 2014, NASA released a Discovery Program 'Draft Announcement of Opportunity' for launch readiness date of December 31, 2021. The final AO was released on November 5, 2014, and on September 30, 2015, NASA selected five mission concepts as finalists, each received $ 3 million for one-year of further study and concept refinement. On January 4, 2017, Lucy and Psyche were selected for
1023-545: A draft of its Discovery 2019 Announcement of Opportunity, which outlined its intent to select up to two missions with launch readiness dates of July 1, 2025 – December 31, 2026, and/or July 1, 2028 – December 31, 2029, as Discovery 15 and 16, respectively. The final Announcement of Opportunity was released on April 1, 2019, and proposal submissions were accepted between then and July 1, 2019. Finalists, announced on February 13, 2020, were: On June 2, 2021, NASA administrator Bill Nelson announced in his "State of NASA" address that
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#17327721166121116-491: A general purpose. The Discovery Program was founded in 1990 to implement the policy of the then-NASA administrator Daniel S. Goldin of " faster, better, cheaper " planetary science missions. Existing NASA programs had specified mission targets and objectives in advance, then sought bidders to construct and operate them. In contrast, Discovery missions are solicited through a call for proposals on any science topic and assessed through peer review . Selected missions are led by
1209-468: A great deal of exploration has been performed by robotic spacecraft missions that have been organized and executed by various space agencies. All planets in the Solar System, plus their major moons along some asteroids and comets , have now been visited to varying degrees by spacecraft launched from Earth. Through these uncrewed missions, humans have been able to get close-up photographs of all
1302-404: A launch in late 2004 and the cost was constrained at about US$ 300 million each. In 1998 five finalists had been selected to receive US$ 375,000 to further mature their design concept. The five proposals were selected out of about 30 with the goal of achieving the best science. Those missions were: Aladdin and MESSENGER were also finalists in the 1997 selection. 26 proposals were submitted to
1395-495: A new mission. As of June 2021, the most recently selected Discovery missions were VERITAS and DAVINCI , the fifteenth and sixteenth missions in the program. In 1989, NASA's Solar System Exploration Division began to define a new strategy for Solar System exploration up to the year 2000. This included a Small Mission Program Group that investigated missions that would be low cost and allow focused scientific questions to be addressed in shorter time than existing programs. The result
1488-413: A proof of Kepler's laws. Newton was able to explain the motions of the planets by hypothesizing a force of gravity acting between all solar system objects in proportion to their mass and an inverse-square law for distance - Newton's law of universal gravitation . Newton's 1687 Philosophiæ Naturalis Principia Mathematica explained this along with Newton's laws of motion , for the first time providing
1581-411: A science instrument or hardware components of an instrument, or for an extended mission for a spacecraft that may differ from its original purpose. However often the funding comes in, there is a selection process with perhaps two dozen concepts. These sometimes get further matured and re-proposed in another selection or program. An example of this is Suess-Urey Mission , which was passed over in favor of
1674-407: A scientist called the principal investigator (PI) and may include contributions from industry, universities or government laboratories. The Discovery Program also includes Missions of Opportunity, which fund U.S. participation in spacecraft operated by other space agencies, for example by contributing a single scientific instrument . It can also be used to re-purpose an existing NASA spacecraft for
1767-464: A small world between Mars and Jupiter. It was considered another planet, but after subsequent discoveries of other small worlds in the same region, it and the others were eventually reclassified as asteroids . By 1846, discrepancies in the orbit of Uranus led many to suspect a large planet must be tugging at it from farther out. John Adams and Urbain Le Verrier 's calculations eventually led to
1860-434: A time scale of 10 ~10 years. It is a potential Earth impactor , about five times larger than the impactor that created Chicxulub crater and led to the extinction of the non-avian dinosaurs . The NEAR Shoemaker probe visited Eros twice, first with a brief flyby in 1998, and then by orbiting it in 2000, when it extensively photographed its surface. On 12 February 2001, at the end of its mission, it landed on
1953-418: A unified explanation for astronomical and terrestrial phenomena. These concepts became the basis of classical mechanics , which enabled future advancements in many fields of physics . The telescope made it possible for the first time to detect objects not visible to the naked eye. This took some time to accomplish, due to various logistical considerations such as the low magnification power of early equipment,
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#17327721166122046-594: A unique element called aether . A later geocentric model developed by Ptolemy attached smaller spheres to a smaller number of large spheres to explain the complex motions of the planets, a device known as deferent and epicycle first developed by Apollonius of Perga . Published in the Almagest , this model of celestial spheres surrounding a spherical Earth was reasonably accurate and predictive, and became dominant among educated people in various cultures, spreading from Ancient Greece to Ancient Rome, Christian Europe,
2139-607: A working group for the program recommended that the first mission should be to a near-Earth asteroid . A series of proposals limited to missions to a near-Earth asteroid missions were reviewed in 1991. What would be the NEAR spacecraft mission was formally selected in December 1993, after which began a 2-year development period prior to launch. NEAR was launched on February 15, 1996, and arrived to orbit asteroid Eros on February 14, 2000. Mars Pathfinder launched on December 4, 1996, and landed on Mars on July 4, 1997, bringing along with it
2232-551: Is 2.67 g/cm , about the same as the density of Earth's crust. NEAR scientists have found that most of the larger rocks strewn across Eros were ejected from a single crater in an impact approximately 1 billion years ago. (The crater involved was proposed to be named "Shoemaker", but is not recognized as such by the International Astronomical Union (IAU), and has been formally designated Charlois Regio.) This event may also be responsible for
2325-401: Is a Mars-crosser asteroid , the first known to come within the orbit of Mars . Objects in such an orbit can remain there for only a few hundred million years before the orbit is perturbed by gravitational interactions. Dynamical system modeling suggests that Eros may evolve into an Earth-crosser within as short an interval as two million years, and has a roughly 50% chance of doing so over
2418-476: Is derived from the Latin word for Sun, Sol (genitive Solis ). Anything related to the Sun is called "solar": for example, stellar wind from the Sun is called solar wind . The first humans had limited understanding of the celestial bodies that could be seen in the sky. The Sun , however, was of immediate interest, as it generates the day-night cycle. Even more, the dawn and sunset always take part at roughly
2511-651: Is known to be the Solar System was regarded as the " whole universe ", so the knowledge of both mostly advanced in parallel. A clear distinction was not made until around the mid-17th century. Since then, incremental knowledge has been gained not only about the Solar System, but also about outer space and its deep-sky objects . The composition of stars and planets was investigated with spectroscopy . Observations of Solar System bodies with other types of electromagnetic radiation became possible with radio astronomy , infrared astronomy , ultraviolet astronomy , X-ray astronomy , and gamma-ray astronomy . Robotic space probes ,
2604-672: The New Horizons probe is the first human-made spacecraft to explore the Kuiper belt. This uncrewed mission flew by Pluto in July 2015. The mission was extended to observe a number of other Kuiper belt objects, including a close flyby of 486958 Arrokoth on New Year's Day, 2019. 433 Eros 433 Eros is a stony asteroid of the Amor group , and the first discovered, and second-largest near-Earth object . It has an elongated shape and
2697-454: The Apollo program landings of humans on the Moon, and space telescopes have vastly increased human knowledge about the atmosphere, geology, and electromagnetic properties of other planets, giving rise to the new field of planetary science . The Solar System is one of many planetary systems in the galaxy. The planetary system that contains Earth is named the "Solar" System. The word "solar"
2790-507: The Kuiper belt ; an icy analogue to the asteroid belt of which such objects as Pluto and Charon were deemed a part, the Kuiper belt objects (KBO). Teams by Mike Brown , Chad Trujillo and David Rabinowitz discovered the trans-Neptunian objects (TNO) Quaoar in 2002, Sedna in 2003, Orcus and Haumea in 2004 and Makemake in 2005, part of the most notable KBOs, some now regarded as dwarf planets . Also in 2005 they announced
2883-661: The Lick Observatory , University of California . Perrine published progress reports in 1906 and 1908. He took 965 photographs with the Crossley Reflector and selected 525 for measurement. A similar program was then carried out, during a closer approach, in 1930–1931 by Harold Spencer Jones . The value of the Astronomical Unit (roughly the Earth-Sun distance) obtained by this program
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2976-580: The Moon was cratered, that the Sun was marked with sunspots , and that Jupiter had four satellites in orbit around it. Christiaan Huygens followed on from Galileo's discoveries by discovering Saturn's moon Titan and the shape of the rings of Saturn . Giovanni Domenico Cassini later discovered four more moons of Saturn and the Cassini division in Saturn's rings. Around 1677, Edmond Halley observed
3069-485: The classical planets (these star-like points visible with the naked eye) with deities , in part due to their puzzling forward and retrograde motion against the otherwise fixed stars , which gave them their nickname of "wanderer stars", πλάνητες ἀστέρες ( planētes asteres ) in Ancient Greek, from which today's word " planet " was derived. Systematic astronomical observations were performed in many areas around
3162-406: The distance to the Moon , with a visual magnitude of +8.1. During rare oppositions, every 81 years, such as in 1975 and 2056, Eros can reach a magnitude of +7.0, which is brighter than Neptune and brighter than any main-belt asteroid except 1 Ceres , 4 Vesta and, rarely, 2 Pallas and 7 Iris . Under this condition, the asteroid actually appears to stop, but unlike the normal condition for
3255-452: The spectroscope , which they used to pioneer the identification of the chemical elements in Earth, and also in the Sun. Around 1862 Father Angelo Secchi developed the heliospectrograph , enabling him to study both the Sun and the stars, and identifying them as things intrinsically of the same kind. In 1868 Jules Janssen and Norman Lockyer discovered a new element in the Sun unknown on Earth, helium , which currently comprises 23.8% of
3348-676: The termination shock , heliosheath, and heliopause . According to NASA , both Voyager probes have encountered the termination shock at a distance of approximately 93 AU from the Sun. The first flyby of a comet occurred in 1985, when the International Cometary Explorer (ICE) passed by the comet Giacobini–Zinner , whereas the first flybys of asteroids were conducted by the Galileo space probe, which imaged both 951 Gaspra (in 1991) and 243 Ida (in 1993) on its way to Jupiter . Launched on January 19, 2006,
3441-467: The 13th and 14th Discovery missions, respectively and launched on 16 October 2021 and 13 October 2023, respectively. Lucy will fly by five Jupiter trojans , asteroids which share Jupiter's orbit around the Sun , orbiting either ahead of or behind the planet. Psyche will explore the origin of planetary cores by orbiting and studying the metallic asteroid 16 Psyche . On December 22, 2018, NASA released
3534-493: The 2000 Discovery solicitation, with budget initially targeted at US$ 300 million. Three candidates were shortlisted in January 2001 for a phase-A design study: Dawn , Kepler space telescope , and INSIDE Jupiter . INSIDE Jupiter was similar to a later New Frontiers mission called Juno ; Dawn was a mission to asteroids Vesta and Ceres , and Kepler was a space telescope mission aimed to discover extrasolar planets . The three finalists received US$ 450,000 to further mature
3627-455: The 40 percent of the Erotian surface that is devoid of craters smaller than 0.5 kilometers across. It was originally thought that the debris thrown up by the collision filled in the smaller craters. An analysis of crater densities over the surface indicates that the areas with lower crater density are within 9 kilometers of the impact point. Some of the lower density areas were found on
3720-465: The English language by 1704, when John Locke used it to refer to the Sun, planets, and comets as a whole. By then it had been stablished beyond doubt that planets are other worlds, then the stars would be other distant suns, so the whole Solar System is actually only a small part of an immensely large universe, and definitively something distinct. Although it is debatable when the Solar System as such
3813-499: The Islamic world, South Asia, and China via inheritance and copying of texts, conquest, trade, and missionaries. It remained in widespread use until the 16th century. Various astronomers, especially those who had access to more precise observations, were skeptical of the geocentric model and proposed alternatives, including the heliocentric theory where the planets and the Earth orbit the Sun. Many proposals did not diffuse outside
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3906-508: The Maragha school in Persia. Kerala -based astronomer Nilakantha Somayaji proposed a geoheliocentric system, in which the planets circled the Sun while the Sun, Moon and stars orbited the Earth. Finally, Polish astronomer Nicolaus Copernicus developed in full a system called Copernican heliocentrism , in which the planets and the Earth orbit the Sun, and the Moon orbits the Earth. Though
3999-402: The Solar System. Telescopic observations resulted in the discovery of moons and rings around planets , and new planets, comets and the asteroids ; the recognition of planets as other worlds, of Earth as another planet, and stars as other suns; the identification of the Solar System as an entity in itself, and the determination of the distances to some nearby stars. For millennia, what today
4092-457: The Sun and Moon were attached; another proposed they were free-floating. All remaining stars were regarded as " fixed " in the background. One important discovery made at different times in different places is that the bright planet sometimes seen near the sunrise (called Phosphorus by the Greeks) and the bright planet sometimes seen near the sunset (called Hesperus by the Greeks) were actually
4185-535: The Sun, Moon, and planets not available to the naked eye. It appeared around 1608 in the Netherlands, and was quickly adopted among European enthusiasts and astronomers to study the skies. Italian polymath Galileo Galilei was an early user and made prolific discoveries, including the phases of Venus , which definitively disproved the arrangement of spheres in the Ptolemaic system. Galileo also discovered that
4278-510: The asteroid's surface using its maneuvering jets. This was the first time a Near Earth asteroid was closely visited by a spacecraft. Surface gravity depends on the distance from a spot on the surface to the center of a body's mass. Eros's surface gravity varies greatly because Eros is not a sphere but an elongated peanut-shaped object. The daytime temperature on Eros can reach about 100 °C (373 K) at perihelion . Nighttime measurements fall near −150 °C (123 K). Eros's density
4371-517: The by-then-late Copernicus' theory was known to Danish astronomer Tycho Brahe , he did not accept it, and proposed his own geoheliocentric Tychonic system . Brahe undertook a substantial series of more accurate observations. German natural philosopher Johannes Kepler at first worked to combine Copernican system with Platonic solids in line with his interpretation of Christianity and an ancient musical resonance theory known as Musica universalis . After becoming an assistant for Brahe, Kepler inherited
4464-481: The cause of the aberration of starlight is the Earth's motion around the Sun), but also accurately revealed, for the first time, the vast distance between the Solar System and the closest stars. Then, in 1859, Robert Bunsen and Gustav Kirchhoff , using the newly invented spectroscope , examined the spectral signature of the Sun and discovered that it was composed of the same elements as existed on Earth, establishing for
4557-556: The confinement of the whole universe , its edge, rotating daily around. Since Hellenistic astronomy and through the Middle Ages , the estimated radius of such sphere was becoming increasingly large, up to inconceivable distances. But by the European Renaissance , the possibility that such a huge sphere could complete a single revolution of 360° around the Earth in only 24 hours was deemed improbable, and this point
4650-554: The discovery of Eris , a scattered disc object initially thought to be larger than Pluto, which would make it the largest object discovered in orbit around the Sun since Neptune. New Horizons ' fly-by of Pluto in July 2015 resulted in more-accurate measurements of Pluto, which is slightly larger, though less massive, than Eris. Radar astronomy is the technique for observing nearby astronomical objects by reflecting radio waves or microwaves off target objects and analyzing their reflections, which provide information about
4743-605: The discovery of Neptune . The excess perihelion precession of Mercury 's orbit led Le Verrier to postulate the intra-Mercurian planet Vulcan in 1859, but that would turn out not to exist: the excess perihelion precession was finally explained by Einstein's general relativity , which displaced Newton's theory as the most accurate description of gravity on large scales. Eventually, new moons were discovered also around Uranus starting in 1787 by Herschel, around Neptune starting in 1846 by William Lassell and around Mars in 1877 by Asaph Hall . Further apparent discrepancies in
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#17327721166124836-604: The first extrasolar planet around a Sunlike star, was discovered. NASA announced in March 2022 that the number of discovered exoplanets reached 5,000, of several types and sizes. Also in 1992, astronomers David C. Jewitt of the University of Hawaii and Jane Luu of the Massachusetts Institute of Technology discovered Albion . This object proved to be the first of a new population, which became known as
4929-466: The first NASA Mars rover, Sojourner . In August 1994, NASA made an Announcement of Opportunity for the next proposed Discovery missions. There were 28 proposals submitted to NASA in October 1994: In February 1995, Lunar Prospector , a lunar orbiter mission, was selected for launch. Three other missions were left to undergo a further selection later in 1995 for the fourth Discovery mission: Stardust , Suess-Urey , and Venus Multiprobe . Stardust ,
5022-507: The first time a physical similarity between Earth and the other bodies visible from Earth. Then, Father Angelo Secchi compared the spectral signature of the Sun with those of other stars, and found them virtually identical. The realisation that the Sun is a star led to a scientifically updated hypothesis that other stars could have planetary systems of their own, though this was not to be proven for nearly 140 years. Observational cosmology began with attempts by William Herschel to describe
5115-575: The launch year. Solar System exploration Discovery and exploration of the Solar System is observation, visitation, and increase in knowledge and understanding of Earth 's "cosmic neighborhood". This includes the Sun , Earth and the Moon , the major planets Mercury , Venus , Mars , Jupiter , Saturn , Uranus , and Neptune , their satellites , as well as smaller bodies including comets , asteroids , and dust . In ancient and medieval times, only objects visible to
5208-521: The local culture, or did not become locally dominant. Aristarchus of Samos had speculated about heliocentrism in Ancient Greece ; Martianus Capella taught in the early Middle Ages that both Mercury and Venus orbit the Sun, while the Moon, the Sun and the other planets orbit the Earth; in Al-Andalus , Arzachel proposed that Mercury orbits the Sun, and heliocentric astronomers worked in
5301-464: The mass in the solar photosphere . As of today, spectroscopes are an important tool to know about the chemical composition of the celestial bodies. By the mid-20th century, new important technologies for remote sensing and observation arose, as radar , radio astronomy and astronautics . In ancient times, there was a common belief in the so-called "sphere of fixed stars ", a giant dome-like structure or firmament centered on Earth which acted as
5394-422: The mission concept. In December 2001, Kepler and Dawn were selected for flight. At this time, only 80 exoplanets had been detected, and the main mission of Kepler to look for more exoplanets, especially Earth-sized. Both Kepler and Dawn were initially projected for launch in 2006. The original Announcement of Opportunity for a Discovery mission released on April 16, 2004. The only candidate for selection for
5487-475: The naked eye—the Sun, the Moon, the five classical planets , and comets , along with phenomena now known to take place in Earth's atmosphere , like meteors and aurorae —were known. Ancient astronomers were able to make geometric observations with various instruments. The collection of precise observations in the early modern period and the invention of the telescope helped determine the overall structure of
5580-616: The novel (and its film adaptation ) Ender's Game by Orson Scott Card , serving as a base for humanity and the location of Command School after having been captured from the invading aliens (the Formics) prior to the initial novel who had used the asteroid as their forward operating base in their previous invasion. In the Space Angel episode 'Visitors from Outer Space' (title text not quite matching narration), Scott McCloud and his crew are forced to destroy Eros by deflecting it into
5673-404: The observations and was directed to mathematically analyze the orbit of Mars. After many failed attempts, he eventually made the groundbreaking discovery that the planets moved around the Sun in ellipses . He formulated and published what are now known as Kepler's laws of planetary motion from 1609 to 1619. This became the dominant model among astronomers, though as with celestial sphere models ,
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#17327721166125766-410: The opposite side of the asteroid but still within 9 kilometers. It is thought that seismic shockwaves propagate through the asteroid, shaking smaller craters into rubble. Since Eros is irregularly shaped, parts of the surface antipodal to the point of impact can be within 9 kilometres of the impact point (measured in a straight line through the asteroid) even though some intervening parts of
5859-416: The orbits of the outer planets led Percival Lowell to conclude that yet another planet, " Planet X ", must lie beyond Neptune. After his death, his Lowell Observatory conducted a search that ultimately led to Clyde Tombaugh 's discovery of Pluto in 1930. Pluto was, however, found to be too small to have disrupted the orbits of the outer planets, and its discovery was therefore coincidental. Like Ceres, it
5952-582: The physical mechanism by which this motion occurred was somewhat mysterious and theories abounded. It took some time for the new theories to diffuse across the world. For example, with the Age of Discovery already well underway, astronomical thought in America was based on the older Greek theories, but newer western European ideas began to appear in writings by 1659. The invention of the telescope revolutionized astronomy, making it possible to see details about
6045-502: The planets and, in the case of landers , perform tests of the soils and atmospheres of some. The first artificial object sent into space was the Soviet satellite Sputnik 1 , launched on 4 October 1957, which successfully orbited Earth until 4 January the following year. The American probe Explorer 6 , launched in 1959, was the first satellite to image Earth from space. The first successful probe to fly by another Solar System body
6138-463: The same impact is believed to have created the thrust fault Hinks Dorsum. A phenomenon named dust ponds were discovered in the asteroid in October 2000. Dust ponds are a phenomenon where pockets of dust are seen in airless celestial bodies. These are smooth deposits of dust accumulated in depressions on the surface of the body (like craters), contrasting from the rocky terrain around them. They typically have different color and albedo compared to
6231-621: The same planet, Venus . Though unclear if motivated by empirical observations, the concept of a spherical Earth apparently first gained intellectual dominance in the Pythagorean school in Ancient Greece in the 5th century BC. Meanwhile, the Pythagorean astronomical system proposed the Earth and Sun and a counter-Earth rotate around an unseen "Central Fire". Influenced by Pythagoran thinking and Plato , philosophers Eudoxus , Callippus , and Aristotle all developed models of
6324-461: The same points of the horizon, which helped to develop the cardinal directions . The Moon was another body of immediate interest, because of its higher visual size. The Lunar phases allowed to measure time in longer periods than those of days, and predict the duration of seasons . Prehistoric beliefs about the structure and origin of the universe were highly diverse, often rooted in religious cosmology , and many are unrecorded. Many associated
6417-541: The same selection process that started once the program was under-way. Mars Pathfinder was salvaged from the idea for a technology and EDL demonstrator from the Mars Environmental Survey program. One of the goals of Pathfinder was to support the Mars Surveyor program. Later missions would be selected by a more sequential process involving Announcements of Opportunity. In the case of NEAR,
6510-575: The shape of the then known universe. In 1785, he proposed the Milky Way was a disk, but assumed the Sun was at the center. This heliocentric theory was overturned by galactocentrism in the 1910s, after more observations by Harlow Shapley placed the Galactic Center relatively far away. In 1992, the first evidence of a planetary system other than our own was discovered, orbiting the pulsar PSR B1257+12 . Three years later, 51 Pegasi b ,
6603-417: The shapes and surface properties of solid bodies, unavailable by other means. Radar can also accurately measure the position and track the movement of such bodies, specially when they are small, as comets and asteroids, as well as to determine distances between objects in the Solar System. In certain cases radar imaging has produced images with up to 7.5-meter resolution. The Moon is comparatively close and
6696-417: The skies and constellations through a telescope , he concluded that the "fixed stars" which had been studied and mapped were only a tiny portion of the massive universe that lay beyond the reach of the naked eye. He also aimed his telescope to the faint strip of the Milky Way , and he found it resolves into countless white star-like spots, presumably farther stars themselves. The term "Solar System" entered
6789-429: The small area of the sky covered in any given observation, and the work involved in comparing multiple observations over different nights. In 1781, William Herschel was looking for binary stars in the constellation of Taurus when he observed what he thought was a new comet. Its orbit revealed that it was a new planet, Uranus , the first ever discovered telescopically. Giuseppe Piazzi discovered Ceres in 1801,
6882-405: The solar system based on concentric spheres . These required more than one sphere per planet in order to account for the complicated curves they traced across the sky. Aristotelian physics used the Earth's place at the center of the universe along with the theory of classical elements to explain phenomena such as falling rocks and rising flames; objects in the sky were theorized to be composed of
6975-533: The son of Aphrodite . He is identified with the planet Venus . Eros was discovered on 13 August 1898 by Carl Gustav Witt at Berlin Urania Observatory and Auguste Charlois at Nice Observatory and temporarily labeled D.Q. Witt was taking a two-hour exposure of beta Aquarii to secure astrometric positions of asteroid 185 Eunike . Eros is named after the Greek god of love , Erōs . It
7068-664: The successful Stardust mission, but was eventually flown as Genesis , while a more extensive mission similar to INSIDE was flown as Juno in the New Frontiers program . Some of these concepts went on to become actual missions, or similar concepts were eventually realized in another mission class. This list is a mix of previous and current proposals. Additional examples of Discovery-class mission proposals include: The first two Discovery missions were Near Earth Asteroid Rendezvous (NEAR) (later called Shoemaker NEAR) and Mars Pathfinder . These initial missions did not follow
7161-411: The surface are more than 9 kilometres away in straight-line distance. A suitable analogy would be the distance from the top centre of a bun to the bottom centre as compared to the distance from the top centre to a point on the bun's circumference: top-to-bottom is a longer distance than top-to-periphery when measured along the surface but shorter than it in direct straight-line terms. Compression from
7254-431: The surrounding areas. The asteroid contains lots of large craters more than 200 m in diameter. Their number is near to the saturation point of these craters. But craters smaller than that are relatively low. Suggesting that some process of erasure has covered them up. The floors of some craters are covered with smooth and flat areas (less than 10° slope). Such dust ponds are characterized by slightly bluer colour compared to
7347-620: The surrounding terrain. 334 of such ponds are identified, with a diameter of 10m. 255 of these are larger than 30m, and 231 (or 91%) are found within 30° from equator. Data from the Near Earth Asteroid Rendezvous spacecraft collected on Eros in December 1998 suggests that it could contain 20 billion tonnes of aluminum and similar amounts of metals that are rare on Earth, such as gold and platinum. On 31 January 2012, Eros passed Earth at 0.17867 AU (26,729,000 km ; 16,608,000 mi ), about 70 times
7440-456: The two Venus missions, VERITAS and DAVINCI , had been selected for development. The two missions will launch between 2031 and 2032. Other proposal submissions for Discovery 15 and 16 missions included: This section includes an image of the Discovery missions' patches or logos, as well as the launch year . This section includes an image of the Discovery missions' rockets, as well as
7533-475: The world are of that type. In 1840 John W. Draper takes a daguerreotype of the Moon, the first astronomical photograph. Since then, astrophotography is a key tool in the observational studies of the skies. Spectroscopy is a method that permits to study materials by means of the light they emit, developed around 1835–1860 by Charles Wheatstone , Léon Foucault , Anders Jonas Ångström and others. Robert Bunsen and Gustav Kirchhoff further develop
7626-522: The world, and started to inform cosmological knowledge, although they were mostly driven by astrological purposes such as divination and/or omens . Early historic civilizations in Egypt , the Levant , pre-Socratic Greece , Mesopotamia , and ancient China , recorded beliefs in a flat Earth . Vedic texts proposed a number of shapes, including a wheel (flat) and a bag (concave), though they likely promote
7719-412: Was Luna 1 , which sped past the Moon in 1959. Originally meant to impact with the Moon, it instead missed its target and became the first artificial object to orbit the Sun. Mariner 2 was the first planetary flyby , passing Venus in 1962. The first successful flyby of Mars was made by Mariner 4 in 1965. Mariner 10 first passed Mercury in 1974. The first probe to explore the outer planets
7812-462: Was Pioneer 10 , which flew by Jupiter in 1973. Pioneer 11 was the first to visit Saturn, in 1979. The Voyager probes performed a Grand Tour of the outer planets following their launch in 1977, with both probes passing Jupiter in 1979 and Saturn in 1980–1981. Voyager 2 then went on to make close approaches to Uranus in 1986 and Neptune in 1989. The two Voyager probes are now far beyond Neptune's orbit, and are on course to find and study
7905-643: Was a request for rapid studies of potential missions and NASA committed funding in 1990. The new program was called "Discovery". The panel assessed several concepts that could be implemented as low-cost programs, selecting NEAR Shoemaker which became the first launch in the Discovery Program on February 17, 1996. The second mission, Mars Pathfinder , launched on December 4, 1996, carried the Sojourner rover to Mars. These provide opportunities to participate in non-NASA missions by providing funding for
7998-501: Was considered definitive until 1968, when radar and dynamical parallax methods started producing more precise measurements. Eros was the first asteroid detected by the Arecibo Observatory 's radar system. Eros was one of the first asteroids visited by a spacecraft, the first one orbited, and the first one soft-landed on. NASA spacecraft NEAR Shoemaker entered orbit around Eros in 2000, and landed in 2001. Eros
8091-479: Was initially considered to be a planet, but after the discovery of many other similarly sized objects in its vicinity it was reclassified in 2006 as a dwarf planet by the IAU. In 1668 Isaac Newton builds his own reflecting telescope , the first fully functional of this kind, and a landmark for future developments as it reduces spherical aberration with no chromatic aberration . Today, most powerful telescopes in
8184-507: Was one of the arguments of Nicholas Copernicus for leaving behind the centuries-old geocentric model. In the sixteenth century, a number of writers inspired by Copernicus, such as Thomas Digges , Giordano Bruno and William Gilbert argued for an indefinitely extended or even infinite universe, with other stars as distant suns, paving the way to deprecate the Aristotelian sphere of the fixed stars. When Galileo Galilei examined
8277-519: Was selected for this opportunity (although a mission of opportunity was selected (Moon Mineralogy Mapper) as part of the AO in 2004). The next Announcement of Opportunity for a Discovery mission was released on January 3, 2006. There were three finalists for this Discovery selection including GRAIL (the eventual winner), OSIRIS, and VESPER. OSIRIS was very similar to the later OSIRIS-REx mission, an asteroid sample-return mission to 101955 Bennu , and Vesper ,
8370-457: Was studied by radar soon after the invention of the technique in 1946, mainly precise measurements of its distance and its surface roughness. Other bodies that have been observed by this means include: By 2018, there have been radar observations of 138 main belt asteroids , 789 near-Earth asteroids , and 20 comets, including 73P/Schwassmann-Wachmann . Since the start of the Space Age ,
8463-415: Was the first evidence that anything other than the planets orbited the Sun, though this had been theorized about comets in the 1st century by Seneca . Around 1704, the term "Solar System" first appeared in English. English astronomer and mathematician Isaac Newton , incidentally building on recent scientific inquiries into the speed at which objects fall, was inspired by claims by rival Robert Hooke of
8556-419: Was the first minor planet to be given a male name; the break with earlier tradition was made because it was the first near-Earth asteroid discovered. During the opposition of 1900–1901, a worldwide program was launched to make parallax measurements of Eros to determine the solar parallax (or distance to the Sun), with the results published in 1910 by Arthur Hinks of Cambridge and Charles D. Perrine of
8649-511: Was truly "discovered", three 19th century observations determined its nature and place in the Universe beyond reasonable doubt. First, by 1835–1838, Thomas Henderson and Friedrich Bessel successfully measured two stellar parallax , an apparent shift in the position of a nearby star created by Earth's motion around the Sun. This was not only a direct, experimental proof of heliocentrism ( James Bradley already did it in 1729 when he discovered
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