Mosaic image of 101955 Bennu consisting of 12 PolyCam images collected on 2 December 2018 by OSIRIS-REx from a range of 24 km (15 mi).
|Discovery site||Lincoln Lab's ETS|
|Discovery date||11 September 1999|
|MPC designation||(101955) Bennu|
|Apollo · NEO · PHA|
|Epoch 31 July 2016 (JD 2457600.5)|
|Uncertainty parameter 0|
|Observation arc||13.36 yr (4880 days)|
|Aphelion||1.3559 au (202.84 Gm)|
|Perihelion||0.89689 au (134.173 Gm)|
|1.1264 au (168.51 Gm)|
|1.20 yr (436.65 d)|
Average orbital speed
|28,000 metres per second (63,000 mph)|
|0° 49m 28.056s / day|
|Earth MOID||0.0032228 au (482,120 km)|
|Venus MOID||0.194 au (29,000,000 km)|
|Mars MOID||0.168 au (25,100,000 km)|
|Jupiter MOID||3.877 au (580.0 Gm)|
|Proper orbital elements|
Proper mean motion
|301.1345 deg / yr|
Proper orbital period
|1.19548 yr |
|±37.5 m 262.5|
|Mass||6.0×1010 kg to ±0.97.8×1010 kg|
|±0.070 g/cm3 1.26|
Equatorial surface gravity
|4.288 h (0.1787 d)|
|176 ± 2°|
|±0.005 0.046 |
| B |
101955 Bennu (provisional designation 1999 RQ36) is a carbonaceous asteroid in the Apollo group discovered by the LINEAR Project on 11 September 1999. It is a potentially hazardous object that is listed on the Sentry Risk Table with the second-highest cumulative rating on the Palermo Technical Impact Hazard Scale. It has a cumulative 1-in-2,700 chance of impacting Earth between 2175 and 2199. It is named after the Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth.
C-type (carbonaceous) asteroids are the most common variety, forming around 75% of known asteroids. They are distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks and minerals. They occur most frequently at the outer edge of the asteroid belt, 3.5 astronomical units (AU) from the Sun, where 80% of the asteroids are of this type, whereas only 40% of asteroids at 2 AU from the Sun are C-type. The proportion of C-types may actually be greater than this, because C-types are much darker than most other asteroid types except for D-types and others that are mostly at the extreme outer edge of the asteroid belt.
The Apollo asteroids are a group of near-Earth asteroids named after 1862 Apollo, discovered by German astronomer Karl Reinmuth in the 1930s. They are Earth-crossing asteroids that have an orbital semi-major axis greater than that of the Earth but perihelion distances less than the Earth's aphelion distance.
The Lincoln Near-Earth Asteroid Research (LINEAR) project is a collaboration of the United States Air Force, NASA, and the MIT's Lincoln Laboratory for the systematic detection and tracking of near-Earth objects. LINEAR was responsible for the majority of asteroid discoveries from 1998 until it was overtaken by the Catalina Sky Survey in 2005. As of 15 September 2011, LINEAR had detected 231,082 new small Solar System bodies, of which at least 2,423 were near-Earth asteroids and 279 were comets. The instruments used by the LINEAR program are located at Lincoln Laboratory's Experimental Test Site (ETS) on the White Sands Missile Range (WSMR) near Socorro, New Mexico.
101955 Bennu has a mean diameter of approximately 492 m (1,614 ft; 0.306 mi) and has been observed extensively with the Arecibo Observatory planetary radar and the Goldstone Deep Space Network.
The Arecibo Observatory is a radio telescope in the municipality of Arecibo, Puerto Rico. This observatory is operated by University of Central Florida, Yang Enterprises and UMET, under cooperative agreement with the US National Science Foundation (NSF). The observatory is the sole facility of the National Astronomy and Ionosphere Center (NAIC), which is the formal name of the observatory. From its construction in the 1960s until 2011, the observatory was managed by Cornell University.
The Goldstone Deep Space Communications Complex (GDSCC), commonly called the Goldstone Observatory, is a satellite ground station located in the Mojave Desert near Barstow in the U.S. state of California. Operated by NASA's Jet Propulsion Laboratory (JPL), its main purpose is to track and communicate with space missions. It is named after Goldstone, California, a nearby gold-mining ghost town.
The NASA Deep Space Network (DSN) is a worldwide network of U.S. spacecraft communication facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA's interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the Solar System and the universe, and supports selected Earth-orbiting missions. DSN is part of the NASA Jet Propulsion Laboratory (JPL). Similar networks are run by Russia, China, India, Japan and the European Space Agency.
Bennu is the target of the OSIRIS-REx mission which is intended to return samples to Earth in 2023 for further study.On 3 December 2018, the OSIRIS-REx spacecraft arrived at Bennu after a two-year journey. Before attempting to obtain a sample from the asteroid, it will map out Bennu's surface in detail and orbit the asteroid to calculate its mass.
The OSIRIS-REx is a NASA asteroid study and sample-return mission. The mission's main goal is to obtain a sample of at least 60 grams (2.1 oz) from 101955 Bennu, a carbonaceous near-Earth asteroid, and return the sample to Earth for a detailed analysis. The material returned is expected to enable scientists to learn more about the formation and evolution of the Solar System, its initial stages of planet formation, and the source of organic compounds that led to the formation of life on Earth. If successful, OSIRIS-REx will be the first U.S. spacecraft to return samples from an asteroid. The Lidar instrument used aboard the OSIRIS-REx was built by Lockheed Martin, in conjunction with the Canadian Space Agency.
A sample-return mission is a spacecraft mission with the goal of collecting and returning samples from an extraterrestrial location to Earth for analysis. Sample-return missions may bring back merely atoms and molecules or a deposit of complex compounds such as loose material ("soil") and rocks. These samples may be obtained in a number of ways, such as soil and rock excavation or a collector array used for capturing particles of solar wind or cometary debris.
Bennu was discovered on 11 September 1999 during a Near-Earth asteroid survey by the Lincoln Near-Earth Asteroid Research (LINEAR). 1999 RQ36 and classified a near-Earth asteroid. Bennu approached close to Earth and it was observed extensively by the Arecibo Observatory and the Goldstone Deep Space Network using radar imaging as Bennu closely approached Earth on 23 September 1999.The asteroid was designated
The name Bennu was selected from more than eight thousand student entries from dozens of countries around the world who entered a "Name That Asteroid!" contest run by the University of Arizona, The Planetary Society, and the LINEAR Project in 2012.Third-grade student Michael Puzio from North Carolina proposed the name in reference to the Egyptian mythological bird Bennu. To Puzio, the OSIRIS-REx spacecraft with its extended TAGSAM arm resembled the Egyptian deity, which is typically depicted as a heron.
The University of Arizona is a public research university in Tucson, Arizona. Founded in 1885, the UA was the first university in the Arizona Territory. As of 2017, the university enrolls 44,831 students in 19 separate colleges/schools, including the University of Arizona College of Medicine in Tucson and Phoenix and the James E. Rogers College of Law, and is affiliated with two academic medical centers. The University of Arizona is governed by the Arizona Board of Regents. The University of Arizona is one of the elected members of the Association of American Universities and is the only representative from the state of Arizona to this group.
The Planetary Society is an American internationally active, non-governmental, nonprofit foundation. It is involved in research, public outreach, and political advocacy for engineering projects related to astronomy, planetary science, and space exploration. It was founded in 1980 by Carl Sagan, Bruce Murray, and Louis Friedman, and has about 60,000 members from more than 100 countries around the world.
North Carolina is a state in the southeastern region of the United States. It borders South Carolina and Georgia to the south, Tennessee to the west, Virginia to the north, and the Atlantic Ocean to the east. North Carolina is the 28th-most extensive and the 9th-most populous of the U.S. states. The state is divided into 100 counties. The capital is Raleigh, which along with Durham and Chapel Hill is home to the largest research park in the United States. The most populous municipality is Charlotte, which is the second-largest banking center in the United States after New York City.
Bennu has a roughly spheroidal shape, resembling a spinning top. Bennu's axis of rotation is tilted 176 degrees to its orbit; The direction of rotation about its axis is retrograde with respect to its orbit. m boulder on its surface, in the southern hemisphere. 10–20Bennu has a fairly smooth shape with one prominent
A spinning top is a toy designed to spin rapidly on the ground, the motion of which causes it to remain precisely balanced on its tip due to its rotational inertia. Such toys have existed since antiquity. Traditionally tops were constructed of wood, sometimes with an iron tip, and would be set in motion by aid of a string or rope coiled around its axis which, when pulled quickly, caused a rapid unwinding that would set the top in motion. Today they are often built of plastic, and modern materials and manufacturing processes allow tops to be constructed with such precise balance that they can be set in motion by a simple twist of the fingers and twirl of the wrist without need for string or rope.
Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is the central object. It may also describe other motions such as precession or nutation of the object's rotational axis. Prograde or direct motion is motion in the same direction as the primary rotates. Rotation is determined by an inertial frame of reference, such as distant fixed stars. However, retrograde and prograde can also refer to an object other than the primary if so described.
There is a well-defined ridge along the equator of Bennu. The presence of this ridge suggests that fine-grained regolith particles have accumulated in this area, possibly because of its low gravity and fast rotation.Observations by the OSIRIS-Rex spacecraft has shown that Bennu is rotating faster over time. This change in Bennu's rotation is caused by the Yarkovsky-O'Keefe-Radzievskii-Paddack effect, or the YORP effect. Due to the uneven emission of thermal radiation from its surface as Bennu rotates in sunlight, the rotation period of Bennu decreases by about one second every 100 years.
Observations of this minor planet by the Spitzer Space Telescope in 2007 gave an effective diameter of ±10 m, which is in line with other studies. It has a low visible geometric albedo of 484±0.005. The thermal inertia was measured and found to vary by approximately 19% during each rotational period. The data suggest that the regolith grain size is moderate, ranging from several millimeters up to a centimeter, and evenly distributed. No emission from a potential dust coma has been detected around Bennu, which puts a limit of 106 0.046 g of dust within a radius of 4750 km.
Astrometric observations between 1999 and 2013 have demonstrated that 101955 Bennu is influenced by the Yarkovsky effect, causing the semimajor axis to drift on average by ±1.5284 meters/year. Analysis of the gravitational and thermal effects has given a bulk density of ρ = ±701260 kg/m3, which is only slightly denser than water. Therefore, the predicted macroporosity is ±10%, suggesting the interior has a rubble pile structure. The estimated mass is 40±0.9)×1010 kg. (7.8
Photometric observations of Bennu in 2005 yielded a synodic rotation period of ±0.0065 h. It has a B-type classification, which is a sub-category of carbonaceous asteroids. Polarimetric observations show that Bennu belongs to the rare F subclass of carbonaceous asteroids, which is usually associated with cometary features. 4.2905 Measurements over a range of phase angles showed a phase function slope of 0.040 magnitudes per degree, which is similar to other near-Earth asteroids with low albedo.
Preliminary spectroscopic surveys of the asteroid's surface by OSIRIS-REx spacecraft, detected the presence of hydrated minerals in the form of clay. While researchers suspect that Bennu was too small to host water, the hydroxyl groups may have come from water presence in its parent body before Bennu split off.
The carbonaceous material that composes Bennu originally came from the breakup of a much larger parent body—a planetoid or a proto-planet. But like nearly all other matter in the Solar System, the origins of its minerals and atoms are to be found in dying stars such as red giants and supernovae. billion years ago during the formation of the Solar System.According to the accretion theory, this material came together 4.5
Bennu's basic mineralogy and chemical nature would have been established during the first 10 million years of the Solar System's formation, where the carbonaceous material underwent some geologic heating and chemical transformation inside a much larger planetoid or a proto-planet capable of producing the requisite pressure, heat and of course the hydration (if need be)—into more complex minerals. km. Simulations suggest a 70% chance it came from the Polana family and a 30% chance it derived from the Eulalia family.Bennu probably began in the inner asteroid belt as a fragment from a larger body with a diameter of 100
Subsequently, the orbit drifted as a result of the Yarkovsky effect and mean motion resonances with the giant planets, such as Jupiter and Saturn. Various interactions with the planets in combination with the Yarkovsky effect modified the asteroid, possibly changing its spin, shape, and surface features.
Cellino et al. have suggested a possible cometary origin for Bennu, based on similarities of its spectroscopic properties with known comets. The estimated fraction of comets in the population of Near Earth asteroids is ±5%. 8%
On average, an asteroid with a diameter of 500 m (1,600 ft; 0.31 mi) can be expected to impact Earth about every 130,000 years or so. A 2010 dynamical study by Andrea Milani and collaborators predicted a series of eight potential Earth impacts by Bennu between 2169 and 2199. The cumulative probability of impact is dependent on physical properties of Bennu that were poorly known at the time, but was found to not exceed 0.071% for all eight encounters. The authors recognized that an accurate assessment of 101955 Bennu's probability of Earth impact would require a detailed shape model and additional observations (either from the ground or from spacecraft visiting the object) to determine the magnitude and direction of the Yarkovsky effect.
The publication of the shape model and of astrometry based on radar observations obtained in 1999, 2005, and 2011, current (as of 2014) [update] best estimate of the impact probability is a cumulative probability of 0.037% in the interval 2175 to 2196. This corresponds to a cumulative score on the Palermo scale of −1.71. If an impact were to occur, the expected kinetic energy associated with the collision would be 1,200 megatons in TNT equivalent (for comparison, TNT equivalent of Little Boy was approx 15 kiloton).made possible an improved estimate of the Yarkovsky acceleration and a revised assessment of the impact probability. The
Bennu will pass 0.005 au (750,000 km ; 460,000 mi ) from Earth on 23 September 2060. The close approach of 2060 causes divergence in the close approach of 2135. On 25 September 2135, the nominal approach distance is 0.002 au (300,000 km; 190,000 mi) from Earth, but Bennu could pass as close as 0.0007 au (100,000 km; 65,000 mi). There is no chance of an Earth impact in 2135. The 2135 approach will create many lines of variations and Bennu may pass through a gravitational keyhole during the 2135 passage which could create an impact scenario at a future encounter. The keyholes are all less than 55 km wide.
On 25 September 2175, there is a 1 in 24,000 chance of an Earth impact, 0.1 au (15,000,000 km ; 9,300,000 mi ). The most threatening virtual impactor is on 24 September 2196 when there is a 1 in 11,000 chance of an Earth impact. There is a cumulative 1 in 2,700 chance of an Earth impact between 2175–2199.but the nominal 2175 approach is in February 2175 at a distance of roughly
Lauretta et al. reported in 2015 their results of a computer simulation, concluding that it is more likely that 101955 Bennu will be destroyed by some other cause:
The orbit of Bennu is intrinsically dynamically unstable, as are those of all NEOs. In order to glean probabilistic insights into the future evolution and likely fate of Bennu beyond a few hundred years, we tracked 1,000 virtual "Bennus" for an interval of 300 Myr with the gravitational perturbations of the planets Mercury–Neptune included. Our results ... indicate that Bennu has a 48% chance of falling into the Sun. There is a 10% probability that Bennu will be ejected out of the inner Solar System, most likely after a close encounter with Jupiter. The highest impact probability for a planet is with Venus (26%), followed by the Earth (10%) and Mercury (3%). The odds of Bennu striking Mars are only 0.8% and there is a 0.2% chance that Bennu will eventually collide with Jupiter.
|Asteroid||Date||Nominal approach distance (LD)||Min. distance (LD)||Max. distance (LD)||Absolute magnitude (H)||Size (meters)|
|(152680) 1998 KJ9||1914-12-31||0.606||0.604||0.608||19.4||279–900|
|(458732) 2011 MD5||1918-09-17||0.911||0.909||0.913||17.9||556–1795|
|(163132) 2002 CU11||1925-08-30||0.903||0.901||0.905||18.5||443–477|
|(153814) 2001 WN5||2028-06-26||0.647||0.647||0.647||18.2||921–943|
|(153201) 2000 WO107||2140-12-01||0.634||0.631||0.637||19.3||427–593|
The small Earth-MOID may result in a weak meteor shower around September 25 radiating from the southern constellation of Sculptor.The meteors are expected to be near the naked eye limit and only produce a Zenith hourly rate of less than 1.
The OSIRIS-REx mission of NASA's New Frontiers program was launched towards 101955 Bennu on September 8, 2016. On December 3, 2018, the spacecraft arrived at the asteroid Bennu after a two-year journey. One week later, at the American Geophysical Union Fall Meeting, investigators announced that OSIRIS-REx had discovered spectroscopic evidence for hydrated minerals on the surface of the asteroid, implying that liquid water was present in Bennu's parent body. OSIRIS-REx is expected to return samples to Earth in 2023.
Bennu was selected from over 000 known asteroids by the OSIRIS-REx selection committee. The primary constraint for selection was close proximity to Earth, since proximity implies low impulse (Δv) required to reach an object from Earth orbit. 500 The criteria stipulated an asteroid in an orbit with low eccentricity, low inclination, and an orbital radius of au . 0.8–1.6 Furthermore, the candidate asteroid for a sample-return mission must have loose regolith on its surface, which implies a diameter greater than 200 meters. Asteroids smaller than this typically spin too fast to retain dust or small particles. Finally, a desire to find an asteroid with pristine carbon material from the early Solar System, possibly including volatile molecules and organic compounds, reduced the list further.
With the above criteria applied, five asteroids remained as candidates for the OSIRIS-REx mission, and Bennu was chosen, in part for its potentially hazardous orbit.
A near-Earth object (NEO) is any small Solar System body whose orbit brings it to proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). If a NEO's orbit crosses the Earth's and the object is larger than 140 meters (460 ft) across, it is considered a potentially hazardous object (PHO). Most known PHOs and NEOs are asteroids, but a small fraction are comets.
Psyche is one of the ten most massive asteroids in the asteroid belt. It is over 200 km (120 mi) in diameter and contains a little less than 1% of the mass of the entire asteroid belt. It is thought to be the exposed iron core of a protoplanet. It is the most massive metallic M-type asteroid. Psyche was discovered by the Italian astronomer Annibale de Gasparis on 17 March 1852 from Naples and named after the Greek mythological figure Psyche.
Phobos is the innermost and larger of the two natural satellites of Mars, the other being Deimos. Both moons were discovered in 1877 by American astronomer Asaph Hall.
Deimos is the smaller and outermost of the two natural satellites of the planet Mars, the other being Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes 30.3 hours to orbit Mars. Deimos is 23,460 km (14,580 mi) from Mars, much further than Mars's other moon, Phobos. It is named for Deimos who in Greek mythology is the twin brother of Phobos, and personifies terror.
NASA's Discovery Program is a series of lower-cost, highly focused American scientific space missions that are exploring the Solar System. It was founded in 1992 to implement then-NASA Administrator Daniel S. Goldin's vision of "faster, better, cheaper" planetary missions. Discovery missions differ from traditional NASA missions where targets and objectives are pre-specified. Instead, these cost-capped missions are proposed and led by a scientist called the Principal Investigator (PI). Proposing teams may include people from industry, small businesses, government laboratories, and universities. Proposals are selected through a competitive peer review process. All of the completed Discovery missions are accomplishing ground-breaking science and adding significantly to the body of knowledge about the Solar System.
25143 Itokawa (; Japanese: イトカワ,いとかわ,糸川 [itokaɰa]; provisional designation 1998 SF36) is a sub-kilometer near-Earth object of the Apollo group and a potentially hazardous asteroid. It was discovered by the LINEAR program in 1998 and later named after Japanese rocket engineer Hideo Itokawa. The strange peanut-shaped S-type asteroid has a rotation period of 12.1 hours and measures approximately 330 meters (1,100 feet) in diameter. Due to its low density and high porosity, Itokawa is considered to be a rubble pile, consisting of numerous boulders of different sizes rather than of a single solid body.
Carl William Hergenrother is an American astronomer and discoverer of minor planets and comets.
In astronomy, a rubble pile is a celestial body that is not a monolith, consisting instead of numerous pieces of rock that have coalesced under the influence of gravity. Rubble piles have low density because there are large cavities between the various chunks that make them up.
Dante Lauretta is a Professor of planetary science and cosmochemistry at the University of Arizona's Lunar and Planetary Laboratory. He is currently serving as the Principal investigator on NASA's OSIRIS-REx mission.
The New Frontiers program is a series of space exploration missions being conducted by NASA with the purpose of researching several of the Solar System bodies, including the dwarf planet Pluto.
The Nysa family is part of the Nysa–Polana complex, the largest cluster of asteroid families in the asteroid belt. It is located in the inner region of the asteroid belt, orbiting the Sun between 2.41 and 2.5 AU. Asteroids in this complex have eccentricities between 0.12 and 0.21 and inclinations of 1.4 to 4.3. The family derives its name from its most massive member, 44 Nysa. It has also been known as the Hertha family(adj. Herthian) named after 135 Hertha.
65803 Didymos , provisional designation 1996 GT, is a sub-kilometer asteroid and synchronous binary system, classified as potentially hazardous asteroid and near-Earth object of both the Apollo and Amor group. It is the target of the proposed AIDA asteroid-mission. The asteroid was discovered in 1996, by the Spacewatch survey at Kitt Peak, and its small 170-meter minor-planet moon was discovered in 2003. Due to its binary nature, it was then named "Didymos", the Greek word for twin.
An Earth trojan is an asteroid that orbits the Sun in the vicinity of the Earth–Sun Lagrangian points L4 (leading 60°) or L5 (trailing 60°), thus having an orbit similar to Earth's. Only one Earth trojan has so far been discovered. The name trojan was first used in 1906 for the Jupiter trojans, the asteroids that were observed near the Lagrangian points of Jupiter's orbit.
162173 Ryugu, provisional designation 1999 JU3, is a near-Earth object and a potentially hazardous asteroid of the Apollo group. It measures approximately 1 kilometer (0.6 mi) in diameter and is a dark object of the rare spectral type Cg, with qualities of both a C-type asteroid and a G-type asteroid. In June 2018, a spacecraft, Hayabusa2, arrived at the asteroid.
(341843) 2008 EV5, provisional designation 2008 EV5, is a sub-kilometer asteroid, classified as a near-Earth object and potentially hazardous asteroid of the Aten group, approximately 400 metres (1,300 feet) in diameter. It was discovered on 4 March 2008, by astronomers of the Mount Lemmon Survey at Mount Lemmon Observatory near Tucson, Arizona, United States.
Hyper-velocity Asteroid Mitigation Mission for Emergency Response (HAMMER) is a concept study by NASA on a spacecraft capable of detonating a nuclear bomb to deflect an asteroid, if it was on a collision course to Earth. The study is a collaboration between the National Nuclear Security Administration, NASA, and two Energy Department weapons labs.
TAGSAM or Touch-and-Go Sample Acquisition Mechanism is a device on the OSIRIS-REx space probe for collection samples from asteroid 101955 Bennu. OR was launched in 2016, and arriving at the asteroid in December 2018 with plans to study the asteroid and return samples to Earth by the early 2020s.