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Rocks/Rocky objects/Asteroids

RocksEdit

 
This image shows the sedimentary rock layers at Zabriskie Point in Death Valley, USA. Credit: Brigitte Werner (werner22brigitte).

Petrology is a branch of geology that studies rocks, and the conditions in which rocks form. Lithology focuses on macroscopic hand-sample or outcrop-scale description of rocks, as in the image on the right, while petrography deals with microscopic details. Petrology benefits from mineralogy, optical mineralogy, geochemistry, and geophysics.

Three branches of petrology focus on the three major rock types: igneous petrology, metamorphic petrology, and sedimentary petrology.

Rocky objectsEdit

 
This is an image of a rock, a diabase with an aphanitic groundmass and plagioclase phenocrysts. Credit: Siim Sepp.

A rocky object is any object, including astronomical objects, composed of one or more types of rocks.

A division of astronomical objects between rocky objects, liquid objects, gaseous objects (including gas giants and stars), and plasma objects may be natural and informative.

This division allows moons like Io to be viewed as rocky objects like Earth, rather than as a satellite around Jupiter.

The astronomy of such objects may be called rocky-object astronomy.

The object imaged on the right is a rock, a diabase with an aphanitic groundmass and plagioclase phenocrysts. It is also a rocky object in part because it is no longer connected to the rest of its original rock. From its rounded appearance it was probably found in a stream bed.

1999 JU3Edit

"Asteroid 1999 JU3 is a so-called carbonaceous, or C-type, space rock — a different type of asteroid than the rocky (S-type) asteroid Itokawa visited by the first Hayabusa. Scientists suspect asteroid 1999 JU3 holds water and organic materials — some of the building blocks of the solar system."[1]

2007 VK184Edit

 
Asteroid 2007 VK184 has been eliminated as Impact Risk to Earth. Credit: Steven Chesley.

"Recent observations have removed from NASA's asteroid impact hazard list the near-Earth object (NEO) known to pose the most significant risk of Earth impact over the next 100 years."[2]

"2007 VK184, an asteroid estimated to be roughly 130 meters in size, has been on NASA's Impact Risk Page maintained by the NEO Program Office at the Jet Propulsion Laboratory (JPL) for several years, with an estimated 1-in-1800 chance of impacting Earth in June 2048. This predicted risk translates to a rating of 1 on the 10-point Torino Impact Hazard Scale. In recent months, 2007 VK184 has been the only known NEO with a non-zero Torino Scale rating."[2]

"2007 VK184 was discovered in November 2007 by the NASA-funded Catalina Sky Survey (CSS) at the University of Arizona and tracked by the CSS and other stations for two months before moving beyond view of ground based telescopes in January 2008."[2]

"But in the early morning hours of March 26 and 27, 2014, Dr. David Tholen of the University of Hawaii sighted 2007 VK184 once again. Using the 3.6-meter-diameter Canada-France-Hawaii Telescope at the Mauna Kea Observatories in Hawaii, he was able to detect and track the asteroid. Because it had not been observed for almost six years, its predicted position was only approximate. Nonetheless, Dr. Tholen was able to find it within the predicted search region, which is called a "recovery." He measured the asteroid's position and movement relative to the background of stars, and forwarded his tracking data to the Minor Planet Center (MPC) in Cambridge, Massachusetts, the central node for the global NEO observer community."[2]

"Although the asteroid will be closer to Earth and brighter in May, I made the recovery attempt in March because I didn't want the position uncertainty to grow so much that it would force a time-consuming search of much more of the sky. The trade-off was increased exposure time to detect such a faint, distant object. Greater atmospheric turbulence on March 26 blurred the images of the asteroid enough to make the detection questionable, but the March 27 images were much better and confirmed the recovery."[3]

"The "Sentry" asteroid monitoring system at JPL automatically retrieved the new observations of 2007 VK184 from the MPC database, updated the orbit for the object, and computed a new impact hazard assessment. This new work shows that 2007 VK184 will pass no closer than 1.9 million kilometers (1.2 million miles) from the Earth in June 2048, with no closer encounters predicted for the foreseeable future. The NEO Program Office removed 2007 VK184 from the Impact Risk Page about three hours after receiving Dr. Tholen's observations from the MPC."[2]

"While these new observations of 2007 VK184 were challenging for Dave Tholen to obtain, they were reported quickly, and the global, distributed NEO impact hazard monitoring system worked smoothly to provide the all-clear for this object."[2]

"JPL's Sentry is an automated monitoring system that continually scans the most current catalog of known asteroids and predicts potential hazards of impacts with Earth over the next 100 years. As additional observations become available, objects will be removed from Sentry's Impact Risk Page when sufficient data become available to eliminate any potential for impact in the projected future. According to the Torino Impact Hazard Scale, developed and used by NEO observers to assess potential impact risks, a rating of 1 indicates a predicted event that "merits careful monitoring," and a rating of zero indicates the predicted event has "no likely consequences.""[2]

"Objects typically appear on the Sentry Impact Risk Page because a limited number of available observations may indicate a potential hazard of impact with Earth but do not provide astronomers enough information to precisely define their orbital movements. Whenever a newly discovered NEO is posted on the Sentry Impact Risk Page, the most likely outcome is that the object will eventually be removed as new observations become available, the object's orbit is more precisely known, and its future motion is more tightly constrained. NASA's NEO Program Office at JPL, which operates Sentry, receives asteroid observations and orbit predictions daily from the MPC. Once an asteroid is classified as a near-Earth object, the Sentry system automatically calculates orbit updates for it as new data become available."[2]

"NASA's Near-Earth Object Observation (NEOO) Program, located in the Planetary Science Division of the Science Mission Directorate at NASA Headquarters in Washington, D.C., is responsible for finding, tracking, and characterizing near-Earth objects (NEOs) - asteroids and comets whose orbits periodically bring them close to Earth. The NEOO Program sponsors internal NASA and external research projects. The Jet Propulsion Laboratory (JPL) in Pasadena, California, manages a NEO Program Office for the Headquarters' NEOO Program and conducts a number of NASA-sponsored NEO projects."[2]

"Asteroid 2007 VK184 is another case study on how our system works."[4]

"We find them, track them, learn as much as we can about those found to be of special interest - an impact hazard or a space mission destination - and we predict and monitor their movement in the inner solar system until we know they are of no more concern."[4]

2012 LZ1Edit

 
This image is of asteroid 2012 LZ1 by the Arecibo Observatory in Puerto Rico using the Arecibo Planetary Radar. Credit: Arecibo Observatory.

The image at right is of asteroid 2012 LZ1 using the Arecibo Planetary Radar.

"On Sunday, June 10, a potentially hazardous asteroid thought to have been 500 meters (0.31 miles) wide was discovered by Siding Spring Observatory in New South Wales, Australia. Fortunately for us, asteroid 2012 LZ1 drifted safely by, coming within 14 lunar distances from Earth on Thursday, June 14."[5]

"Asteroid 2012 LZ1 is actually bigger than thought… in fact, it is quite a lot bigger. 2012 LZ1 is one kilometer wide (0.62 miles), double the initial estimate."[5]

Asteroid "2012 LZ1′s surface is really dark, reflecting only 2-4 percent of the light that hits it — this contributed to the underestimated initial optical observations. Looking for an asteroid the shade of charcoal isn’t easy."[5]

“This object turned out to be quite a bit bigger than we expected, which shows how important radar observations can be, because we’re still learning a lot about the population of asteroids”.[1]

“The sensitivity of our radar has permitted us to measure this asteroid’s properties and determine that it will not impact the Earth at least in the next 750 years”.[6]

1 CeresEdit

 
Ceres is seen by the Hubble Space Telescope, Advanced Camera for Surveys (ACS). The contrast has been enhanced to reveal surface details. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), and L. McFadden (University of Maryland, College Park).
 
Ceres as seen by the Dawn spacecraft, 19 February 2015. Credit: NASA, JPL-Caltech, UCLA, MPS, DLR, IDA.
 
Hemispheric topographic maps of Ceres, centered on 60° and 240° east longitude (July 2015). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

High-resolution ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface which was nicknamed "Piazzi" in honour of the discoverer of Ceres.[7] This was thought to be a crater. Later near-infrared images with a higher resolution taken over a whole rotation with the Keck telescope using adaptive optics showed several bright and dark features moving with the dwarf planet's rotation.[8][9]

"This pair of images shows color-coded maps from NASA's Dawn mission, revealing the highs and lows of topography on the surface of dwarf planet Ceres."[10]

"The map at left is centered on terrain at 60 degrees east longitude; the map at right is centered on 240 degrees east longitude."[10]

"The color scale extends about 5 miles (7.5 kilometers) below the surface in indigo to 5 miles (7.5 kilometers) above the surface in white."[10]

"The topographic map was constructed from analyzing images from Dawn's framing camera taken from varying sun and viewing angles. The map was combined with an image mosaic of Ceres and projected as an orthographic projection."[10]

"The well-known bright spots in the center of Ceres northern hemisphere in the image at right retain their bright appearance, although they are color-coded in the same green elevation of the crater floor in which they sit."[10]

"Note: The elevation scale used for this topographic map product differs slightly from the scale used to create PIA19605."[10]

2 PallasEdit

 
This is an ultraviolet image of Pallas showing its flattened shape taken by the Hubble Space Telescope. Credit: NASA.

"Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered (after Ceres), and one of the largest in the Solar System. It is estimated to comprise 7% of the mass of the asteroid belt,[11] and its diameter of 544 kilometres (338 mi) is slightly larger than that of 4 Vesta. It is however 10–30% less massive than Vesta,[12] placing it third among the asteroids.

3 JunoEdit

3 Juno is a siliceous asteroid type S(IV).[13]

4 VestaEdit

 
This is a composite Dawn spacecraft image of Vesta.
 
Hubble's Wide Field Planetary Camera 2 to snapped this new image of Vesta on May 14 and 16, 2007. Credit: NASA; ESA; L. McFadden and J.Y. Li (University of Maryland, College Park); M. Mutchler and Z. Levay (Space Telescope Science Institute, Baltimore); P. Thomas (Cornell University); J. Parker and E.F. Young (Southwest Research Institute); and C.T. Russell and B. Schmidt (University of California, Los Angeles).

"The [NASA's Dawn spacecraft] Framing Camera (FC) discovered enigmatic orange material on Vesta. FC images revealed diffuse orange ejecta around two impact craters, 34-km diameter Oppis, and 30-km diameter Octavia, as well as numerous sharp-edge orange units in the equatorial region."[14] The spacecraft "entered orbit around asteroid (4) Vesta in July 2011 for a year-long mapping orbit."[14]

"Using Dawn’s Gamma Ray and Neutron Detector, ... Global Fe/O and Fe/Si ratios are consistent with [howardite, eucrite, and diogenite] HED [meteorite] compositions."[15]

"To prepare for the Dawn spacecraft's visit to Vesta, astronomers used Hubble's Wide Field Planetary Camera 2 to snap new images of the asteroid. The image at right was taken on May 14 and 16, 2007. Using Hubble, astronomers mapped Vesta's southern hemisphere, a region dominated by a giant impact crater formed by a collision billions of years ago. The crater is 285 miles (456 kilometers) across, which is nearly equal to Vesta's 330-mile (530-kilometer) diameter. If Earth had a crater of proportional size, it would fill the Pacific Ocean basin. The impact broke off chunks of rock, producing more than 50 smaller asteroids that astronomers have nicknamed "vestoids." The collision also may have blasted through Vesta's crust. Vesta is about the size of Arizona."[16]

"Previous Hubble images of Vesta's southern hemisphere were taken in 1994 and 1996 with the wide-field camera. In this new set of images, Hubble's sharp "eye" can see features as small as about 37 miles (60 kilometers) across. The image shows the difference in brightness and color on the asteroid's surface. These characteristics hint at the large-scale features that the Dawn spacecraft [sees] when it arrives at Vesta."[16]

"Hubble's view reveals extensive global features stretching longitudinally from the northern hemisphere to the southern hemisphere. The image also shows widespread differences in brightness in the east and west, which probably reflects compositional changes. Both of these characteristics could reveal volcanic activity throughout Vesta. The size of these different regions varies. Some are hundreds of miles across."[16]

"The brightness differences could be similar to the effect seen on the Moon, where smooth, dark regions are more iron-rich than the brighter highlands that contain minerals richer in calcium and aluminum. When Vesta was forming 4.5 billion years ago, it was heated to the melting temperatures of rock. This heating allowed heavier material to sink to Vesta's center and lighter minerals to rise to the surface."[16]

"Astronomers combined images of Vesta in two colors to study the variations in iron-bearing minerals. From these minerals, they hope to learn more about Vesta's surface structure and composition."[16]

"The simplest model for the genesis of the HED meteorites involves a series of partial melting and crystallization events [1] of a small parent body whose bulk composition is more or less consistent with cosmic abundances but is depleted in the moderately volatile elements Na and K [2]."[17]

"Why should both Vesta and the Moon be rich in oxidized Fe but depleted in Na and K?"[17]

"How did the HEDs get here from Vesta? The discovery of a string of Vesta-like asteroids in orbits linking Vesta to nearby orbital resonances [5] has shown that [...] arguments [...] for material originating at Vesta to reach Earth-crossing orbits are [...] valid."[17]

"An alternative theory is based on electromagnetic heating during an episode of strong solar wind from the early proto-Sun when our star experienced a T Tauri phase, as predicted by modern stellar astrophysics."[18]

6 HebeEdit

 
This is visual spotting of 6 Hebe. Credit: NASA.

6 Hebe is a siliceous asteroid of subtype IV [S(IV)].[13]

The image on the right is a photograph of 6 Hebe (the brightest spot) in 2004.

"Compositional analysis of 2007 LE reveal Fs17 and Fa19 values, which are consistent with the Fa and Fs values for the H-type ordinary chondrites (Fs14.5–18 and Fa16–20) and of Asteroid (6) Hebe (Fs17 and Fa15)."[19]

"It is probable that the H-chondrites and IIE irons came from (6) Hebe (Gaffey and Gilbert, 1998), though caveats exist (e.g., Rubin and Bottke, 2009)."[19]

8 FloraEdit

8 Flora may be ambiguously a type S(II-III) siliceous asteroid.[13]

9 MetisEdit

9 Metis is a siliceous asteroid.[13]

11 ParthenopeEdit

11 Parthenope is a siliceous asteroid type S(IV).[13]

12 VictoriaEdit

12 Victoria is a siliceous asteroid of subtype II [S(II)].[13]

15 EunomiaEdit

15 Eunomia is a siliceous asteroid of subtype III [S(III)].[13]

16 PsycheEdit

 
A three-dimensional model of 16 Psyche was computed using light curve inversion techniques. Credit: Josef Ďurech, Vojtěch Sidorin, Astronomical Institute of the Charles University.
 
This is an animation of the revolution of 16 Psyche. Credit: WilyD.
 
Asteroid 16 Psyche displays significant variations in radar albedo with rotation. Credit: Imke de Pater.

A "huge, metallic asteroid named 16 Psyche [...] resides" in the asteroid belt.[20]

16 Psyche is "a 130-mile-wide (210 kilometers) metallic asteroid that may be the core of an ancient, Mars-size planet. Violent collisions billions of years ago might have stripped away the layers of rock that once lay atop this metallic object."[21]

"16 Psyche is the only known object of its kind in the solar system, and this is the only way humans will ever visit a core. We learn about inner space by visiting outer space."[21]

The "asteroid Psyche displays significant variations in radar and optical albedo with rotation."[22]

"16 Psyche [is] the largest M-class asteroid in the main belt."[22]

"18 radar imaging and 6 continuous wave runs in November and December 2015, [were] combined [...] with 16 continuous wave runs from 2005 and 6 recent adaptive-optics (AO) images (Drummond et al., 2016) to generate a three-dimensional shape model of Psyche."[22]

The "shape model has dimensions 279 × 232 × 189 km (± 10%), Deff = 226 ± 23 km, and is 6% larger than, but within the uncertainties of, the most recently published size and shape model generated from the inversion of lightcurves (Hanus et al., 2013). Psyche is roughly ellipsoidal but displays a mass-deficit over a region spanning 90° of longitude. There is also evidence for two ∼50–70 km wide depressions near its south pole. Their size and published masses lead to an overall bulk density estimate of 4500 ± 1400 kg·m−3. Psyche's mean radar albedo of 0.37 ± 0.09 is consistent with a near-surface regolith composed largely of iron-nickel and ∼40% porosity. Its radar reflectivity varies by a factor of 1.6 as the asteroid rotates, suggesting global variations in metal abundance or bulk density in the near surface."[22]

18 MelpomeneEdit

18 Melpomene is a siliceous asteroid type S(V).[13]

20 MassaliaEdit

20 Massalia is a siliceous asteroid type S(VI).[13]

25 PhocaeaEdit

25 Phocaea is a siliceous asteroid type S(IV).[13]

26 ProserpinaEdit

26 Proserpina is a siliceous asteroid of subtype II [S(II)].[13]

27 EuterpeEdit

27 Euterpe is a siliceous asteroid type S(IV).[13]

29 AmphitriteEdit

29 Amphitrite is a siliceous asteroid type S(V).[13]

33 PolyhymniaEdit

33 Polyhymnia is a siliceous asteroid type S(IV).[13]

37 FidesEdit

37 Fides is a siliceous asteroid type S(V).[13]

39 LaetitiaEdit

39 Laetitia is a siliceous asteroid of subtype II [S(II)].[13]

42 IsisEdit

42 Isis is a siliceous asteroid of subtype I [S(I)].[13]

43 AriadneEdit

43 Ariadne is a siliceous asteroid of subtype III [S(III)].[13]

57 MnemosyneEdit

57 Mnemosyne is a siliceous asteroid type S(VII).[13]

63 AusoniaEdit

63 Ausonia is a siliceous asteroid of subtype III [S(III)].[13]

"Ausonia is classed ambiguously as type S(II-III)."[13]

67 AsiaEdit

67 Asia is a siliceous asteroid type S(IV).[13]

68 LetoEdit

68 Leto is a siliceous asteroid of subtype II [S(II)].[13]

80 SapphoEdit

80 Sappho is a siliceous asteroid type S(IV).[13]

82 AlkmeneEdit

82 Alkmene is a siliceous asteroid type S(VI).[13]

89 JuliaEdit

89 Julia is a siliceous asteroid.[13]

101 HelenaEdit

101 Helena is a siliceous asteroid type S(V).[13]

113 AmaltheaEdit

113 Amalthea is a siliceous asteroid of subtype I [S(I)].[13]

115 ThyraEdit

115 Thyra is a siliceous asteroid of subtype III [S(III)].[13]

158 KoronisEdit

170 MariaEdit

197 AreteEdit

"More than 150 years after the discovery of 4 Vesta in 1807, Hertz (1966) made the first asteroid mass determination by analyzing its perturbation on 197 Arete."[23]

221 EosEdit

243 IdaEdit

 
This is the first image of the asteroid Ida using the green 559 nm filter onboard the Galileo spacecraft. Credit: NASA/JPL.
 
This is an approximately natural color picture of the asteroid 243 Ida on August 28, 1993. Credit: NASA/JPL.

"This is the first full picture [on the right] showing both asteroid 243 Ida and its newly discovered moon to be transmitted to Earth from the National Aeronautics and Space Administration's (NASA's) Galileo spacecraft--the first conclusive evidence that natural satellites of asteroids exist. Ida, the large object, is about 56 kilometers (35 miles) long. Ida's natural satellite is the small object to the right. This portrait was taken by Galileo's charge-coupled device (CCD) camera on August 28, 1993, about 14 minutes before the Jupiter-bound spacecraft's closest approach to the asteroid, from a range of 10,870 kilometers (6,755 miles). Ida is a heavily cratered, irregularly shaped asteroid in the main asteroid belt between Mars and Jupiter--the 243rd asteroid to be discovered since the first was found at the beginning of the 19th century. Ida is a member of a group of asteroids called the Koronis family. The small satellite, which is about 1.5 kilometers (1 mile) across in this view, has yet to be given a name by astronomers. It has been provisionally designated '1993 (243) 1' by the International Astronomical Union. ('1993' denotes the year the picture was taken, '243' the asteroid number and '1' the fact that it is the first moon of Ida to be found.) Although appearing to be 'next' to Ida, the satellite is actually in the foreground, slightly closer to the spacecraft than Ida is. Combining this image with data from Galileo's near-infrared mapping spectrometer, the science team estimates that the satellite is about 100 kilometers (60 miles) away from the center of Ida. This image, which was taken through a green filter, is one of a six-frame series using different color filters. The spatial resolution in this image is about 100 meters (330 feet) per pixel."[24]

On the second lower right is an approximately natural color image of the asteroid 243 Ida. "There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right-hand edge (the limb). This is a combination of more reflected blue light and greater absorption of near infrared light, suggesting a difference in the abundance or composition of iron-bearing minerals in these areas."[25]

246 AsporinaEdit

246 Asporina is an A-type asteroid.[26]

253 MathildeEdit

 
253 Mathilde is a C-type asteroid measuring about 50 km across, covered in craters half that size. Credit: NEAR Shoemaker.

Mathide is a carbonaceous (C) asteroid.

"The masses of 253 Mathide (Yeomans et al., 1998) and Eros (Yeomans et al., 2000) are the first two asteroid masses determined by observing the perturbation of a spacecraft in the vicinity of the asteroid."[23]

258 TycheEdit

258 Tyche is a siliceous asteroid type S(V).[13]

264 LibussaEdit

264 Libussa is a siliceous asteroid type S(V).[13]

289 NenettaEdit

289 Nenetta is an A asteroid.[13]

335 RobertaEdit

335 Roberta is a blue asteroid.[27]

354 EleonoraEdit

354 Eleonora is a siliceous asteroid of subtype I [S(I)].[13]

364 IsaraEdit

364 Isara is a siliceous asteroid of subtype II [S(II)].[13]

387 AquitaniaEdit

389 IndustriaEdit

389 Industria is a siliceous asteroid type S(V).[13]

433 ErosEdit

"In 2000, 433 Eros became the first asteroid to be orbited by a spacecraft, NEAR Shoemaker (Yeomans et al., 2000)."[23]

446 AeternitasEdit

446 Aeternitas is an A asteroid.[13]

532 HerculinaEdit

532 Herculina is a siliceous asteroid of subtype III [S(III)].[13]

584 SemiramisEdit

584 Semiramis is a siliceous asteroid type S(IV).[13]

674 RacheleEdit

674 Rachele is a siliceous asteroid of subtype VII [S(VII)].[13]

951 GaspraEdit

The "Galileo flyby images of 951 Gaspra suggest the presence of some regolith on that 16- by 12-km object (e.g., Belton et al. 1992)."[13]

980 AnacostiaEdit

1036 GanymedEdit

1036 Ganymed is a siliceous asteroid type S(VI-VII).[13]

3103 EgerEdit

4179 ToutatisEdit

 
This is a Goldstone radar image of asteroid 4179 Toustatis. Credit: Steve Ostro, JPL.

At right is a Goldstone radar image of the asteroid 4179 Toutatis on November 26, 1996.

The "images were recorded at NASA's Deep Space Network 70-meter and 34-meter radio/radar antennas in Goldstone, CA, and the 305-meter Arecibo Radio Telescope in Puerto Rico."[28]

"It's amazing that the shape of Toutatis can be determined so accurately from ground-based observations".[29]

"This technology will provide us with startling, close-up views of thousands of asteroids that orbit near the Earth."[29]

"We used the computer to mathematically create a three- dimensional model of the surface and rotation of Toutatis".[30]

"It's as though we put a clay model in space and molded it until it matched the appearance of the actual asteroid."[30]

"The video is of particular interest as Toutatis nears Earth and makes its closest approach on Friday, Nov. 29, when it will pass by at a distance of 3.3 million miles (5.3 million kilometers), or about 14 times the distance from the Earth to the Moon. In 2004, Toutatis will pass only four lunar distances from Earth, closer than any known Earth- approaching object expected to pass by in the next 60 years."[28]

"Toutatis poses no significant threat to Earth, at least for a few hundred years".[31]

"The discovery that we live in an asteroid swarm is important for the future of humanity".[31]

"These leftover debris from planetary formation can teach us a good deal about the formation of our Solar System. Asteroids also contain valuable minerals and many are the cheapest possible destinations for space missions."[31]

On September 29, 2004 the asteroid 4179 Toutatis made a particularly close approach (within 4 LD, or lunar distances) from Earth. The next close approach is November 9, 2008, but it will be five times more distant. It is about 4.6 km by 2.4 km in size.

99942 ApophisEdit

There is some concern that the asteroid 99942 Apophis could impact Earth on April 13, 2036. It is about 210 - 330 meters in size. The probability of a collision is currently esitmated to be 1 in 45,000. These calculations are uncertain due to another close encounter in 2029 which will modify the orbit of the asteroid, making a collision either more or less likely. New measurements possible in 2011-2013 will likely confirm that the asteroid will miss the Earth.

HypothesesEdit

  1. Asteroids are any-size rocky astronomical objects.

See alsoEdit

ReferencesEdit

  1. 1.0 1.1 Ellen Howell (June 22, 2012). Asteroid 2012 LZ1 Just Got Supersized. Discovery Communications, LLC. Retrieved 2013-10-24.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Steven Chesley (2 April 2014). Asteroid 2007 VK184 Eliminated as Impact Risk to Earth. Pasadena, California USA: NASA/JPL. Retrieved 2015-09-02.
  3. David Tholen (2 April 2014). Asteroid 2007 VK184 Eliminated as Impact Risk to Earth. Pasadena, California USA: NASA/JPL. Retrieved 2015-09-02.
  4. 4.0 4.1 Lindley Johnson (2 April 2014). Asteroid 2007 VK184 Eliminated as Impact Risk to Earth. Pasadena, California USA: NASA/JPL. Retrieved 2015-09-02.
  5. 5.0 5.1 5.2 Ian O'Neill (June 22, 2012). Asteroid 2012 LZ1 Just Got Supersized. Discovery Communications, LLC. Retrieved 2013-10-24.
  6. Mike Nolan (June 22, 2012). Asteroid 2012 LZ1 Just Got Supersized. Discovery Communications, LLC. Retrieved 2013-10-24.
  7. Parker, J. W.; Stern, Alan S.; Thomas Peter C.; et al.. "Analysis of the first disk-resolved images of Ceres from ultraviolet observations with the Hubble Space Telescope 2002". The Astrophysical Journal 123 (1): 549–557. doi:10.1086/338093. 
  8. Carry, Benoit; et al. (November). "Near-Infrared Mapping and Physical Properties of the Dwarf-Planet Ceres 2007". Astronomy & Astrophysics 478 (1): 235–244. doi:10.1051/0004-6361:20078166. 
  9. Staff (2006-10-11). Keck Adaptive Optics Images the Dwarf Planet Ceres. Adaptive Optics. Retrieved 2007-04-27.
  10. 10.0 10.1 10.2 10.3 10.4 10.5 Karen Boggs (28 July 2015). PIA19607: Topographic Maps of Ceres' East and West Hemispheres. Pasadena, California USA: NASA/JPL. Retrieved 2015-11-09.
  11. Elena V. Pitjeva. "High-Precision Ephemerides of Planets—EPM and Determination of Some Astronomical Constants". Solar System Research 2005 39 (3): 176. doi:10.1007/s11208-005-0033-2. http://iau-comm4.jpl.nasa.gov/EPM2004.pdf. 
  12. James Baer and Steven R. Chesley (2008). "Astrometric masses of 21 asteroids, and an integrated asteroid ephemeris". Celestial Mechanics and Dynamical Astronomy 100 (2008): 27–42. doi:10.1007/s10569-007-9103-8. http://www.springerlink.com/content/h747307j43863228/fulltext.pdf. Retrieved 2008-11-11. 
  13. 13.00 13.01 13.02 13.03 13.04 13.05 13.06 13.07 13.08 13.09 13.10 13.11 13.12 13.13 13.14 13.15 13.16 13.17 13.18 13.19 13.20 13.21 13.22 13.23 13.24 13.25 13.26 13.27 13.28 13.29 13.30 13.31 13.32 13.33 13.34 13.35 13.36 13.37 13.38 13.39 13.40 Michael J. Gaffey, Jeffrey F. Bell, R. Hamilton Brown, Thomas H. Burbine, Jennifer L. Piatek, Kevin L. Reed, and Damon A. Chaky (December 1993). "Mineralogical variations within the S-type asteroid class". Icarus 106 (2): 573-602. http://www.mtholyoke.edu/~tburbine/gaffey.icarus.1993.pdf. Retrieved 2015-09-03. 
  14. 14.0 14.1 L Le Corre, V Reddy, KJ Becker (October 2012). "Nature of Orange Ejecta Around Oppia and Octavia Craters on Vesta from Dawn Framing Camera". American Astronomical Society, DPS meeting (44). 
  15. Thomas H. Prettyman, David W. Mittlefehidt, Naoyuki Yamashita, David J. Lawrence, Andrew W. Beck, William C. Feldman, Timothy J. McCoy, Harry Y. McSween, Michael J. Toplis, Timothy N. Titus, Pasquale Tricarico, Robert C. Reedy, John S. Hendricks, Olivier Forni, Lucille Le Corre, Jian-Yang Li, Hugau Mizzon, Vishnu Reddy, Carol A. Raymond, Christopher T. Russell (October 2012). "Elemental Mapping by Dawn Reveals Exogenic H in Vesta's Regolith". Science 338 (6104): 242-6. doi:10.1126/science.1225354. 
  16. 16.0 16.1 16.2 16.3 16.4 Ray Villard and Lucy McFadden (June 20, 2007). Hubble Images of Asteroids Help Astronomers Prepare for Spacecraft Visit. Space Telescope Science Institute, Baltimore, Md USA: HubbleSite. Retrieved 2013-12-22.
  17. 17.0 17.1 17.2 G. J. Consolmagno (January 1996). "Cosmogonic Implications of the HED-Vesta Connection". Workshop on Evolution of Igneous Asteroids: Focus on Vesta and the HED Meteorites: 6. http://adsabs.harvard.edu/abs/1996eiaf.conf....6C. Retrieved 2013-12-22. 
  18. L. Bussolino, R. Sommat, C. Casaccit, V. Zappala, A. Cellino, and M. Di Martino (January 1996). "A Space Mission to Vesta: General Considerations". Workshop on Evolution of Igneous Asteroids: Focus on Vesta and the HED Meterorites (http://adsabs.harvard.edu/abs/1996eiaf.conf....5B): 5. 
  19. 19.0 19.1 Sherry K. Fieber-Beyer, Michael J. Gaffey, William F. Bottke, Paul S. Hardersen (2015). "Potentially hazardous Asteroid 2007 LE: Compositional link to the black chondrite Rose City and Asteroid (6) Hebe". Icarus 250: 430-7. doi:10.1016/j.icarus.2014.12.021. http://www.boulder.swri.edu/~bottke/Reprints/Fieber_Beyer_2015_Icarus_250_430_Link_2007LE_Black_Chondrite.pdf. Retrieved 2015-09-24. 
  20. Mike Wall (4 January 2017). NASA Unveils 2 New Missions to Study Truly Strange Asteroids. Space.com. Retrieved 2017-01-09.
  21. 21.0 21.1 Lindy Elkins-Tanton (4 January 2017). NASA Unveils 2 New Missions to Study Truly Strange Asteroids. Space.com. Retrieved 2017-01-09.
  22. 22.0 22.1 22.2 22.3 Imke de Pater (27 October 2016). Prof. Imke de Pater Confirms Asteroid 16 Psyche to be the Largest Metal Asteroid in the Main Belt. Retrieved 2017-01-09.
  23. 23.0 23.1 23.2 James L. Hilton (January 1, 2002). William Frederick Bottke. ed. Asteroid Masses and Densities, In: Asteroids III. Tucson, Arizona USA: University of Arizona Press. pp. 103-20. ISBN 0816522812. http://books.google.com/books?hl=en&lr=&id=JwHTyO6IHh8C&oi=fnd&pg=PA235&ots=AI9aRiuWcM&sig=2dO3vVO2i-v_oO0zGwe_zzg_p0M. Retrieved 2014-01-10. 
  24. Sue Lavoie (February 1, 1996). PIA00136: Asteroid Ida and Its Moon. Pasadena, California USA: NASA/JPL. Retrieved 2013-01-25.
  25. Sue Lavoie (January 29, 1996). PIA00069: Ida and Dactyl in Enhanced Color. Pasadena, California USA: NASA/JPL. Retrieved 2013-06-01.
  26. V. Reddy, P. S. Hardersen, M. J. Gaffey, and P. A. Abell (2005). Mineralogic and Temperature-Induced Spectral Investigations of A-type Asteroids 246 Asporina and 446 Aeternitas, In: Lunar and Planetary Science (PDF). XXXVI. USRA. p. 2. Retrieved 2015-09-04.CS1 maint: Multiple names: authors list (link)
  27. Bin Yang and David Jewitt (September 2010). "Identification of Magnetite in B-type Asteroids". The Astronomical Journal 140 (3): 692. doi:10.1088/0004-6256/140/3/692. http://iopscience.iop.org/1538-3881/140/3/692. Retrieved 2013-06-01. 
  28. 28.0 28.1 Don Savage and Jane Platt (November 27, 1996). Images of Asteroid 4179 Toutatis. Washington, DC USA: NASA. Retrieved 2013-10-24.
  29. 29.0 29.1 Eric De Jong (November 27, 1996). Images of Asteroid 4179 Toutatis. Washington, DC USA: NASA. Retrieved 2013-10-24.
  30. 30.0 30.1 Scott Hudson (November 27, 1996). Images of Asteroid 4179 Toutatis. Washington, DC USA: NASA. Retrieved 2013-10-24.
  31. 31.0 31.1 31.2 Steven Ostro (November 27, 1996). Images of Asteroid 4179 Toutatis. Washington, DC USA: NASA. Retrieved 2013-10-24.

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