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101955 Bennu

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101955 Bennu
Grey asteroid
Mosaic image of Bennu after two years of observation by OSIRIS-REx
Discovery[1]
Discovered byLINEAR
Discovery siteLincoln Lab's ETS
Discovery date11 September 1999
Designations
(101955) Bennu
Pronunciation/ˈbɛnuː/[2]
Named after
Bennu
1999 RQ36
Apollo · NEO · PHA · risk listed
Orbital characteristics[1]
Epoch 1 January 2011 (JD 2455562.5)
Uncertainty parameter 0
Observation arc21.06 yr (7693 days)
Aphelion1.3559 au (202.84 Gm)
Perihelion0.8969 au (134.17 Gm)
1.1264 au (168.51 Gm)
Eccentricity0.2038
1.1955 yr (436.65 d)
28.0 km/s (63,000 mph)
101.7039°
0° 49m 28.056s / day
Inclination6.0349°
2.0609°
66.2231°
Earth MOID0.0032228 au (482,120 km)
Venus MOID0.194 au (29,000,000 km)[3]
Mars MOID0.168 au (25,100,000 km)[3]
Jupiter MOID3.877 au (580.0 Gm)
TJupiter5.525
Proper orbital elements[4]
0.21145
5.0415°
301.1345 deg / yr
1.19548 yr
(436.649 d)
Physical characteristics[5]
Dimensions565 m × 535 m × 508 m (1854 ft × 1755 ft × 1667 ft)[1]
245.03±0.08 m (804±0.262 ft)
Equatorial radius
282.37±0.06 m (926.4±0.197 ft)
Polar radius
249.25±0.06 m (817.74±0.197 ft)
0.782±0.004 km2 (0.302±0.002 sq mi)
Volume0.0615±0.0001 km3
Mass(7.329±0.009)×1010 kg
Mean density
1.190±0.013 g/cm3
Equatorial surface gravity
6.27 micro-g[6] (61.5 μm/s2)
Equatorial escape velocity
20 cm/s
4.296057±0.000002 h
177.6±0.11°
North pole right ascension
+85.65±0.12°
North pole declination
−60.17±0.09°
0.044±0.002
Surface temp. min mean max
Kelvin[7] 236 259 279
Fahrenheit -34.6 6.8 42.8
Celsius -37 -14 6
B[1][5]
F[8]
20.9

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 and has the highest cumulative rating on the Palermo Technical Impact Hazard Scale.[9] It has a cumulative 1-in-1,750 chance of impacting Earth between 2178 and 2290 with the greatest risk being on 24 September 2182.[10][11] It is named after Bennu, the ancient Egyptian mythological bird associated with the Sun, creation, and rebirth.

101955 Bennu has a mean diameter of 490 m (1,610 ft; 0.30 mi) and has been observed extensively by the Arecibo Observatory planetary radar and the Goldstone Deep Space Network.[5][12][13]

Bennu was the target of the OSIRIS-REx mission that returned samples of the asteroid to Earth.[14][15][16] The spacecraft, launched in September 2016, arrived at the asteroid two years later and mapped its surface in detail, seeking potential sample collection sites.[17] Analysis of the orbits allowed calculation of Bennu's mass and its distribution.[18] In October 2020, OSIRIS-REx briefly touched down and collected a sample of the asteroid's surface.[19][20][21] A capsule containing the sample was returned and landed on Earth in September 2023, with distribution and analysis of the sample ongoing.[22][23][24] On 15 May 2024, an overview of preliminary analytical studies on the returned samples was reported.[25]

Discovery and observation

[edit]
Series of Goldstone radar images in 1999 showing Bennu's rotation

Bennu was discovered on 11 September 1999 during a Near-Earth asteroid survey by the Lincoln Near-Earth Asteroid Research (LINEAR).[3] The asteroid was given the provisional designation 1999 RQ36 and classified as a near-Earth asteroid.[26] Bennu 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.[27][12]

Naming

[edit]

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.[1][28] 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.[1]

Its features will be named after birds and bird-like creatures in mythology.[29]

Physical characteristics

[edit]
Animation of Bennu rotating, imaged by OSIRIS-REx in December 2018.

Bennu has a roughly spheroidal shape, resembling a spinning top. Bennu's axis of rotation is tilted 178 degrees to its orbit; the direction of rotation about its axis is retrograde with respect to its orbit.[5] While the initial ground based radar observations indicated that Bennu had a fairly smooth shape with one prominent 10–20 m boulder on its surface,[30] high resolution data obtained by OSIRIS-REx revealed that the surface is much rougher with more than 200 boulders larger than 10 m on the surface, the largest of which is 58 m across.[5] The boulders contain veins of high albedo carbonate minerals believed to have formed prior to the formation of the asteroid due to hot water channels on the much larger parent body.[31][32] The veins range from 3 to 15 centimeters wide, and can be over one meter in length, much bigger than carbonate veins seen in meteorites.[32]

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 (about once every 4.3 hours).[30] Observation by the OSIRIS-REx spacecraft has shown that Bennu is rotating faster over time.[33] This change in Bennu's rotation is caused by the Yarkovsky–O'Keefe–Radzievskii–Paddack effect.[33] 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.[33]

Observations of this minor planet by the Spitzer Space Telescope in 2007 gave an effective diameter of 484±10 m, which is in line with other studies. It has a low visible geometric albedo of 0.046±0.005. The thermal inertia was measured and found to vary by approximately 19% during each rotational period. It was based on this observation that scientists (incorrectly) estimated a moderate regolith grain size, ranging from several millimeters up to a centimeter, evenly distributed. No emission from a potential dust coma has been detected around Bennu, which puts a limit of 106 g of dust within a radius of 4750 km.[34]

Astrometric observations between 1999 and 2013 have demonstrated that 101955 Bennu is influenced by the Yarkovsky effect, causing the semimajor axis of its orbit to drift on average by 284±1.5 meters/year. Analysis of the gravitational and thermal effects has given a bulk density of ρ = 1190±13 kg/m3, which is only slightly denser than water. Therefore, the predicted macroporosity is 40±10%, suggesting the interior has a rubble pile structure or even hollows.[35] The estimated mass is (7.329±0.009)×1010 kg.[5]

Photometry and spectroscopy

[edit]

Photometric observations of Bennu in 2005 yielded a synodic rotation period of 4.2905±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.[8] 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.[36]

Before OSIRIS-REx, spectroscopy indicated a correspondence with the CI and/or CM carbonaceous chondrite meteorites,[37][38][39] including carbonaceous-chondrite mineral magnetite.[40][41][42] Magnetite, a spectrally prominent[43][44] water product[45][46][47] but destroyed by heat,[47] is an important proxy of astronomers[48][49][50] including OSIRIS-REx staff.[51]

Water

[edit]

According to Dante Lauretta,[52] OSIRIS-REx Principal Investigator, "Bennu appears to be a very water-rich target, and water is the most interesting and perhaps the most lucrative commodity that you would mine from an asteroid".[53][54]

Predicted beforehand,[55] Dante Lauretta (University of Arizona) reiterates that Bennu is water-rich- already detectable while OSIRIS-REx was still technically in approach.[56]

Preliminary spectroscopic surveys of the asteroid's surface by OSIRIS-REx confirmed magnetite and the meteorite-asteroid linkage,[57][58][59] dominated by phyllosilicates.[60][61][62] Phyllosilicates, among others, hold water.[63][64][65] Bennu's water spectra were detectable on approach,[58][66] reviewed by outside scientists,[67][43] then confirmed from orbit.[40][68][69][70]

OSIRIS-REx observations have resulted in a (self-styled) conservative estimate of about 7 x 108 kg water in one form alone, neglecting additional forms. This is a water content of ~1 wt.%, and potentially much more. In turn this suggests transient pockets of water beneath Bennu's regolith. The surficial water may be lost from the collected samples. However, if the sample return capsule maintains low temperatures, the largest (centimeter-scale) fragments may contain measurable quantities of adsorbed water, and some fraction of Bennu's ammonium compounds.[70] A separate estimate, including other forms of water storage, is 6.2 wt%.[71]

NASA and university sample facilities are preparing to secure, study, and curate the sample, predicted to be rich in water and organic compounds.[72][73][74]

The German SAL (Sample Analysis Laboratory) is preparing to receive cosmochemical water from Ryugu, Bennu, and other airless bodies.[75]

Further information: Asteroidal water and 162173 Ryugu § Water

Activity

[edit]

Bennu is an active asteroid,[76][77][78][79] sporadically emitting plumes of particles[80][81] and rocks as large as 10 cm (3.9 in),[82][83] (not dust, defined as tens of micrometers).[84][85] Scientists hypothesize the releases may be caused by thermal fracturing, volatile release through dehydration of phyllosilicates, pockets of subsurface water,[70] and/or meteoroid impacts.[83]

Before the arrival of OSIRIS-REx, Bennu had displayed polarization consistent with Comet Hale-Bopp and 3200 Phaethon, a rock comet.[8] Bennu, Phaethon, and inactive Manx comets[86] are examples of active asteroids.[87][88][78] B-type asteroids displaying a blue color in particular, may be dormant comets,[89][90][91][92][70] similar to Ryugu but at an earlier stage.[93] If the IAU declares Bennu to be a dual-status object, its comet designation would be P/1999 RQ36 (LINEAR).[94]

Asteroid Bennu ejecting particles
6 January 2019
Particle trajectories from four 2019 ejection events (video; 0:43)
19 January 2019
OSIRIS-REx mission[83][33][95]

Surface features

[edit]
Asteroid Bennu regolith surface
Wide angle shot of the Northern Hemisphere of Bennu, imaged by OSIRIS-REx at an altitude of approximately 1.8 km (1.1 mi)
Bennu's regolith-covered surface as imaged by OSIRIS-REx
The Nightingale sample site imaged by OSIRIS-REx at touchdown. The circular TAGSAM head in the center of the frame is 0.30 m (1 ft) in diameter.

All geological features on Bennu are named after various species of birds and bird-like figures in mythology.[96] The first features to be named were the final four candidate OSIRIS-REx sample sites, which were given unofficial names by the team in August 2019.[97] On 6 March 2020 the IAU announced the first official names for 12 Bennu surface features, including regiones (broad geographic regions), craters, dorsa (ridges), fossae (grooves or trenches) and saxa (rocks and boulders).[98]

Analysis showed that the particles making up Bennu's exterior are loosely packed and lightly bound to each other; "The spacecraft would have sunk into Bennu had it not fired its thrusters to back away immediately after it grabbed dust and rock from the asteroid's surface."[99] Analysis also revealed that the Sun's heat fractures rocks on Bennu in just 10,000 to 100,000 years instead of millions of years as was thought before.[100]

Candidate sample sites

[edit]
Final four OSIRIS-REx candidate sample sites[101]
Name Location Description
Nightingale 56°N 43°E Abundant fine-grained material with a large variation in color. Primary sample collection site.[102]
Kingfisher 11°N 56°E A relatively new crater with the highest water signature of all four sites.
Osprey 11°N 80°E Located on a low albedo patch with a large variety of rocks. Backup sample collection site.[102]
Sandpiper 47°S 322°E Located between two young craters, located in rough terrain. Minerals vary in brightness with hints of hydrated minerals.

On 12 December 2019, after a year of mapping Bennu's surface, a target site was announced. Named Nightingale, the area is near Bennu's north pole and lies inside a small crater within a larger crater. Osprey was selected as the backup sample site.[102]

The final four candidate OSIRIS-REx sample sites

IAU named features

[edit]
Map of Bennu showing the locations of the IAU-named surface features
List of official IAU-named Bennu surface features[103]
Name Named after Location
Aellopus Saxum Aello, one of the half-bird half-woman Harpy sisters from Greek mythology 25.44°N 335.67°E
Aetos Saxum Aetos, childhood playmate of the god Zeus who was turned into an eagle from Greek mythology 3.46°N 150.36°E
Amihan Saxum Amihan, bird deity from Philippine mythology 17.96°S 256.51°E
Benben Saxum Benben, Ancient Egyptian primordial mound that arose from the primordial waters Nu 45.86°S 127.59°E
Boobrie Saxum Boobrie, shapeshifting entity from Scottish mythology that often takes the form of a giant water bird 48.08°N 214.28°E
Camulatz Saxum Camulatz, one of four birds in the K'iche' creation myth in Maya mythology 10.26°S 259.65°E
Celaeno Saxum Celaeno, one of the half-bird half-woman Harpy sisters from Greek mythology 18.42°N 335.23°E
Ciinkwia Saxum Ciinkwia, thunder beings from Algonquian mythology that look like giant eagles 4.97°S 249.47°E
Dodo Saxum Dodo, a dodo bird character from Alice's Adventures in Wonderland 32.68°S 64.42°E
Gamayun Saxum Gamajun, prophetic bird from Slavic mythology 9.86°N 105.45°E
Gargoyle Saxum Gargoyle, dragon-like monster with wings 4.59°N 92.48°E
Gullinkambi Saxum Gullinkambi, rooster from Norse mythology that lives in Valhalla 18.53°N 17.96°E
Huginn Saxum Huginn, one of two ravens that accompany the god Odin in Norse mythology 29.77°S 43.25°E
Kongamato Saxum Kongamato, giant flying creature from Kaonde mythology 5.03°N 66.31°E
Muninn Saxum Muninn, one of two ravens that accompany the god Odin in Norse mythology 29.34°S 48.68°E
Ocypete Saxum Ocypete, one of the half-bird half-woman Harpy sisters from Greek mythology 25.09°N 328.25°E
Odette Saxum Odette, princess that turns into the White Swan in Swan Lake 44.86°S 291.08°E
Odile Saxum Odile, the Black Swan from Swan Lake 42.74°S 294.08°E
Pouakai Saxum Poukai, monstrous bird from Maori mythology 40.45°S 166.75°E
Roc Saxum Roc, giant bird of prey from Arabic mythology 23.46°S 25.36°E
Simurgh Saxum Simurgh, benevolent bird that possesses all knowledge from Iranian mythology 25.32°S 4.05°E
Strix Saxum Strix, bird of ill omen from Classical mythology 13.40°N 88.26°E
Thorondor Saxum Thorondor, the King of the Eagles in Tolkien's Middle-earth 47.94°S 45.10°E
Tlanuwa Regio Tlanuwa, giant birds from Cherokee mythology 37.86°S 261.70°E

Origin and evolution

[edit]

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.[104] According to the accretion theory, this material came together 4.5 billion years ago during the formation of the Solar System.

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 hydration (if need be)—into more complex minerals.[30] Bennu probably began in the inner asteroid belt as a fragment from a larger body with a diameter of 100 km.[105] Simulations suggest a 70% chance it came from the Polana family and a 30% chance it derived from the Eulalia family.[106] Impactors on boulders of Bennu indicate that Bennu has been in near Earth orbit (separated from the main asteroid belt) for 1–2.5 million years.[107]

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.[108]

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 objects is 8%±5%.[8] This includes rock comet 3200 Phaethon, discovered and still numbered as an asteroid.[109][110]

Orbit

[edit]
Diagram of the orbits of Bennu and the inner planets around the Sun

Bennu orbits the Sun with a period of 1.19 years (435 days) as of 2022.[3] Earth gets as close as about 480,000 km (0.0032 au) from its orbit around 23 to 25 September. On 22 September 1999 Bennu passed 0.0147 au from Earth, and six years later on 20 September 2005 it passed 0.033 au from Earth.[1] The next close approaches of less than 0.04 au will be 30 September 2054 and then 23 September 2060, which will perturb the orbit slightly. Between the close approach of 1999 and that of 2060, Earth completes 61 orbits and Bennu 51. An even closer approach will occur on 25 September 2135 around 0.0014 au (see table).[1] In the 75 years between the 2060 and 2135 approaches, Bennu completes 64 orbits, meaning its period will have changed to 1.17 years (427 days).[111] The Earth approach of 2135 will increase the orbital period to about 1.24 years (452 days).[111] Before the 2135 Earth approach, Bennu will be at its maximum distance from Earth on 27 November 2045 at a distance of 2.34 AU (350 million km).[112]

Bennu approaches less than 0.05AU
Position uncertainty and increasing divergence[1]
Date JPL SBDB
nominal geocentric
distance (AU) 		uncertainty
region
(3-sigma)
2054-09-30 0.039299 AU (5.8790 million km) ±7 km
2060-09-23 0.005008 AU (749.2 thousand km) ±5 km
2080-09-22 0.015630 AU (2.3382 million km) ±3 thousand km
2135-09-25 0.001364 AU (204.1 thousand km) ±20 thousand km
(virtual impactor)
2182-09-24[10]		 ≈0.3 AU (40 million km) (Gravity Simulator)[113][114]
1.1 AU (160 million km) (NEODyS)[115]		 ±370 million km

Possible Earth impact

[edit]

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.[116] 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.[117] 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[27] made possible an improved estimate of the Yarkovsky acceleration and a revised assessment of the impact probability. In 2014, the best estimate of the impact probability was a cumulative probability of 0.037% in the interval 2175 to 2196.[118] 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 Tsar Bomba, the most powerful nuclear weapon ever tested, was approximately 54 megatons,[10] and that of the Tunguska event, the most energetic impact event in recorded history, has been estimated at 3–5 megatons,[119] though another estimate is 20–30 megatons[120]).

The 2021 orbit solution extended the virtual impactors from the year 2200 to the year 2300 and slightly increased the cumulative Palermo impact scale to −1.42. The solution included the estimated gravitational effect of 343 other asteroids, representing about 90% of the total mass of the main asteroid belt.[11]

2060/2135 close approaches

[edit]
Animation of 101955 Bennu's position relative to the Earth, as both orbit the Sun, in the years 2128 to 2138. 2135 close approach is shown near the end of the animation.
   Earth ·   101955 Bennu

Bennu will pass 0.005 au (750,000 km; 460,000 mi) from Earth on 23 September 2060,[1] while for comparison the Moon's average orbital distance (lunar distance) is 384,402 km (238,856 mi) and will only change to 384,404 km in 50 years time. Bennu will be too dim to be seen with common binoculars.[121] The close approach of 2060 causes divergence in the close approach of 2135. On 25 September 2135, the Earth approach distance is 0.00136 au (203,000 km; 126,000 mi) ±20 thousand km.[1] There is no chance of an Earth impact in 2135.[122][10] 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 ~20 km wide with some keyholes being only 5 meters wide.[123]

2182

[edit]

The most threatening virtual impactor is on Tuesday, 24 September 2182 when there is a 1 in 2,700 chance of an Earth impact,[10] but the asteroid could be as far as the Sun is from Earth.[115] To impact Earth on 24 September 2182 Bennu must pass through a keyhole roughly 5 km wide on 25 September 2135.[123] The next two biggest risks occur in 2187 (1:14,000) and 2192 (1:26,000).[10] There is a cumulative 1 in 1,800 chance of an Earth impact between 2178 and 2290.[10]

Long term

[edit]

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.[108]

Asteroids of absolute magnitude less than 21 passing less than 1 lunar distance from Earth
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
2017 VW13 2001-11-08 0.373 0.316 3.236 20.7 153–494
(153814) 2001 WN5 2028-06-26 0.647 0.647 0.647 18.2 921–943
99942 Apophis 2029-04-13 0.0989 0.0989 0.0989 19.7 310–340
2005 WY55 2065-05-28 0.865 0.856 0.874 20.7 153–494
101955 Bennu 2135-09-25 0.531 0.507 0.555 20.19 472–512
(153201) 2000 WO107 2140-12-01 0.634 0.631 0.637 19.3 427–593

Meteor shower

[edit]

As an active asteroid with a small minimum orbit intersection distance from Earth, Bennu may be the parent body of a weak meteor shower. Bennu particles would radiate around 25 September from the southern constellation of Sculptor.[124] The meteors are expected to be near the naked eye visibility limit and only produce a Zenith hourly rate of less than 1.[124]

Exploration

[edit]

OSIRIS-REx

[edit]
Main article: OSIRIS-REx
The successful October 2020 sample collection, showing OSIRIS-REx touching down on the Nightingale sample site

The OSIRIS-REx mission of NASA's New Frontiers program was launched towards 101955 Bennu on 8 September 2016. On 3 December 2018, the spacecraft arrived at the asteroid Bennu after a two-year journey.[17] 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 before it split off.[125][5]

On 20 October 2020, OSIRIS-REx descended to the asteroid and "pogo-sticked off"[19] it while successfully collecting a sample.[126] On 7 April 2021, OSIRIS-REx completed its final flyover of the asteroid and began slowly drifting away from it.[127] On 10 May 2021, the departure was completed with OSIRIS-REx still managing to contain the asteroid sample.[24] OSIRIS-REx returned samples to Earth in 2023[128] via a capsule-drop by parachute, ultimately, from the spacecraft to the Earth's surface in Utah on 24 September 2023.[19]

Shortly after the sample container was retrieved and transferred to an airtight chamber at the Johnson Space Center in Houston, Texas, the lid on the container was opened. Scientists commented that they "found black dust and debris on the avionics deck of the OSIRIS-REx science canister" on the initial opening. Further study is planned. On 11 October 2023, the recovered capsule was opened to reveal a "first look" at the asteroid sample contents.[129] On 13 December 2023, further studies of the returned sample were reported and revealed organic molecules as well as unknown materials which require more study to have a better idea of their composition and makeup.[130][131] On 11 January 2024, NASA reported finally fully opening, after three months of trying, the recovered container with samples from the Bennu asteroid.[132][133][134] The total weight of the recovered material weighed 121.6 g (4.29 oz), over twice the mission's goal.[135] On 15 May 2024, an overview of preliminary analytical studies on the returned samples was reported.[25]

Selection

[edit]

The asteroid Bennu was selected from over half a million 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.[136] The criteria stipulated an asteroid in an orbit with low eccentricity, low inclination, and an orbital radius of 0.8–1.6 au.[137] 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.[137]

  •   OSIRIS-REx –   101955 Bennu –   Earth
  • Trajectory in the Solar System from 9 August 2016 to 24 September 2023
    Trajectory in the Solar System from 9 August 2016 to 24 September 2023
  • Trajectory around 101955 Bennu from 25 December 2018
    Trajectory around 101955 Bennu from 25 December 2018
  • Touchdown on Bennu
    Touchdown on Bennu

Returned samples

[edit]
The bulk Bennu sample in the glovebox. (a) Sample obtained from the top of the Mylar flap (left two trays) and scooped from beneath it (right two trays). (b) Sample poured from the TAGSAM into eight trays.[138]
Phosphate in a mottled particle (OREX-803009-101). (a) Visible light microscopy image of a dark particle with an outer crust of high-reflectance material. (b–d) SEM images showing progressively zoomed view of a fragment of the particle that split off along a high-reflectance vein, revealing material similar to the outer crust, with a blocky friable texture and consisting of Na, Mg, and P.[138]

The OSIRIS-REx mission successfully returned approximately 120 grams of material from Bennu to Earth in September 2023. The returned material is predominantly very dark, with reflectance values consistent with observations of Bennu's surface, though it contains some brighter inclusions and particles. Particle sizes in the sample span a wide range, from submicron dust to rocks measuring about 3.5 cm in length. Mineralogical analysis shows that the sample is rich in hydrated minerals, particularly Mg-rich phyllosilicates, confirming predictions from remote sensing data. Other major components include magnetite, sulfides, carbonates, and organic compounds. An unexpected discovery was the presence of phosphate minerals in some samples, including Mg, Na-rich phosphates found as veins and crusts in some particles.[138]

The elemental composition of the Bennu samples closely resembles that of CI chondrite meteorites. However, the Bennu material shows some distinct isotopic ratios. The average oxygen isotopic composition places Bennu in the same region of oxygen three-isotope space as CI and CY chondrites, as well as samples from asteroid Ryugu. The carbon content of the samples (4.5–4.7 wt%) is higher than that found in known meteorites and Ryugu samples. The presence of presolar grains in the samples indicates that some of the material has remained largely unprocessed since the formation of the solar system. Presolar silicon carbide and graphite were identified, with abundances of 52+12
−10 ppm and 12+7
−5 ppm respectively, similar to unheated chondrite samples.[138]

Evidence suggests that the samples come from at least two different lithologies on Bennu's surface. Three predominant types of particles were identified: hummocky, angular, and mottled. These show distinct densities, with hummocky particles having the lowest average density (1.55±0.07 g/cm3) and mottled particles the highest (1.77±0.04 g/cm3). Spectral analysis of the samples shows a redder slope from 0.4 to 2.5 μm compared to Bennu's global spectrum, potentially indicating differences in particle size, surface texture, or space weathering between the sampled material and the asteroid's surface.[138]

Since 3 November 2023, a part of the sample is exhibited at the Hall of Meteorites of the National Museum of Natural History (Washington, DC).[139] Another portion of the sample was exhibited by NASA at the International Astronautical Congress in Milan, Italy, from 14 to 18 October 2024.[140][141]

See also

[edit]

References

[edit]
  1. ^ a b c d e f g h i j k "JPL Small-Body Database Browser: 101955 Bennu (1999 RQ36)" (Solution #118: 2020-10-03 last observation. Solution includes non-gravitational parameters). Jet Propulsion Laboratory. 7 January 2021. Archived from the original on 19 March 2018. Retrieved 28 March 2021.
  2. ^ "Bennu". Dictionary.com Unabridged (Online). n.d.
  3. ^ a b c d "(101955) Bennu = 1999 RQ36 Orbit". Minor Planet Center. Retrieved 21 March 2018.
  4. ^ "(101955) Bennu". NEODyS. University of Pisa. Retrieved 1 December 2015.
  5. ^ a b c d e f g Lauretta, D.S. (19 March 2019). "The unexpected surface of asteroid (101955) Bennu". Nature. 568 (7750): 55–60. Bibcode:2019Natur.568...55L. doi:10.1038/s41586-019-1033-6. PMC 6557581. PMID 30890786.
  6. ^ Barnouin, O.S. (19 March 2019). "Shape of (101955) Bennu indicative of a rubble pile with internal stiffness". Nature Geoscience. 12 (4): 247–252. Bibcode:2019NatGe..12..247B. doi:10.1038/s41561-019-0330-x. PMC 6505705. PMID 31080497.
  7. ^ "Planetary Habitability Calculators". Planetary Habitability Laboratory. University of Puerto Rico at Arecibo. Archived from the original on 18 October 2021. Retrieved 6 December 2015.
  8. ^ a b c d Hergenrother, Carl W.; Maria Antonietta Barucci; Barnouin, Olivier; Bierhaus, Beau; Binzel, Richard P.; Bottke, William F.; Chesley, Steve; Clark, Ben C.; Clark, Beth E.; Cloutis, Ed; Christian Drouet d'Aubigny; Delbo, Marco; Emery, Josh; Gaskell, Bob; Howell, Ellen; Keller, Lindsay; Kelley, Michael; Marshall, John; Michel, Patrick; Nolan, Michael; Rizk, Bashar; Scheeres, Dan; Takir, Driss; Vokrouhlický, David D.; Beshore, Ed; Lauretta, Dante S. (2018). "Unusual polarimetric properties of (101955) Bennu: similarities with F-class asteroids and cometary bodies". Monthly Notices of the Royal Astronomical Society: Letters. 481 (1): L49 – L53. arXiv:1808.07812. Bibcode:2018MNRAS.481L..49C. doi:10.1093/mnrasl/sly156. S2CID 119226483.
  9. ^ "Sentry Risk Table". NASA/JPL Near-Earth Object Program Office. Archived from the original on 11 September 2016. Retrieved 20 March 2018. (Use Unconstrained Settings)
  10. ^ a b c d e f g "101955 1999 RQ36: Earth Impact Risk Summary". NASA. Jet Propulsion Laboratory. 14 July 2021. Retrieved 14 August 2021.
  11. ^ a b Farnocchia, Davide; Chesley, Steven R.; Takahashi, Yu (2021). "Ephemeris and hazard assessment for near-Earth asteroid (101955) Bennu based on OSIRIS-REx data". Icarus. 369: 114594. Bibcode:2021Icar..36914594F. doi:10.1016/j.icarus.2021.114594.
  12. ^ a b "Goldstone Delay-Doppler Images of 1999 RQ36". Asteroid Radar Research. Jet Propulsion Laboratory. Archived from the original on 30 August 2000.
  13. ^ Hudson, R.S.; Ostro, S.J.; Benner, L.A.M. (2000). "Recent Delay-Doppler Radar Asteroid Modeling Results: 1999 RQ36 and Craters on Toutatis". Bulletin of the American Astronomical Society. 32: 1001. Bibcode:2000DPS....32.0710H.
  14. ^ Corum, Jonathan (8 September 2016). "NASA Launches the Osiris-Rex Spacecraft to Asteroid Bennu". The New York Times. Retrieved 9 September 2016.
  15. ^ Chang, Kenneth (8 September 2016). "The Osiris-Rex Spacecraft Begins Chasing an Asteroid". The New York Times. Retrieved 9 September 2016.
  16. ^ Brown, Dwayne; Neal-Jones, Nancy (31 March 2015). "Release 15-056 – NASA's OSIRIS-REx Mission Passes Critical Milestone". NASA. Retrieved 4 April 2015.
  17. ^ a b Chang, Kenneth (3 December 2018). "NASA's Osiris-Rex Arrives at Asteroid Bennu After a Two-Year Journey". The New York Times. Retrieved 12 February 2021.
  18. ^ Plait, Phil (4 December 2018). "Welcome to Bennu!". SYFY Wire. Retrieved 5 December 2018.
  19. ^ a b c Chang, Kenneth (20 October 2020). "Seeking Solar System's Secrets, NASA's OSIRIS-REX Mission Touches Bennu Asteroid". The New York Times. Retrieved 12 February 2021.
  20. ^ Hautaluoma, Grey; Johnson, Alana; Jones, Nancy Neal; Morton, Erin (29 October 2020). "Release 20-109 – NASA's OSIRIS-REx Successfully Stows Sample of Asteroid Bennu". NASA. Retrieved 30 October 2020.
  21. ^ Chang, Kenneth (29 October 2020). "NASA's Asteroid Mission Packs Away Its Cargo. Next Stop: Earth". The New York Times. Retrieved 12 February 2021.
  22. ^ Miller, Katrina (24 September 2023). "A NASA Spacecraft Comes Home With an Asteroid Gift for Earth – The seven-year OSIRIS-REX mission ended on Sunday [9/23/2023] with the return of regolith from the asteroid Bennu, which might hold clues about the origins of our solar system and life. + comment". The New York Times. Archived from the original on 25 September 2023. Retrieved 25 September 2023.
  23. ^ Chang, Kenneth (10 May 2021). "Bye-Bye, Bennu: NASA Heads Back to Earth With Asteroid Stash in Tow – The OSIRIS-REX mission will spend two years cruising home with space rock samples that could unlock secrets of the early solar system". The New York Times. Retrieved 11 May 2021.
  24. ^ a b Marcia Dunn, Associated Press (10 May 2021). "NASA spacecraft begins 2-year trip home with asteroid rubble". WJHL. Retrieved 10 May 2021.
  25. ^ a b Nicitopoulos, Theo (15 May 2024). "NASA's asteroid Bennu samples have rocks unlike any meteorite ever found – Early results from NASA's OSIRIS-REx mission to Bennu have uncovered exotic versions of chondrules – rocks commonly found in meteorites". Astronomy. Archived from the original on 16 May 2024.
  26. ^ "All That is Known About Bennu". The Planetary Society. Retrieved 28 September 2023.
  27. ^ a b Nolan, M.C.; Magri, C.; Howell, E.S.; Benner, L.A.M.; Giorgini, J.D.; Hergenrother, C.W.; Hudson, R.S.; Lauretta, D.S.; Margot, J.L.; Ostro, S.J.; Scheeres, D.J. (2013). "Shape model and surface properties of the OSIRIS-REx target Asteroid (101955) Bennu from radar and lightcurve observations". Icarus. 226 (1): 629–640. Bibcode:2013Icar..226..629N. doi:10.1016/j.icarus.2013.05.028. ISSN 0019-1035.
  28. ^ Murphy, Diane (1 May 2013). "Nine-Year-Old Names Asteroid Target of NASA Mission in Competition Run By The Planetary Society". The Planetary Society. Retrieved 20 August 2016.
  29. ^ Hille, Karl (8 August 2019). "Asteroid's features to be named after mythical birds". NASA.gov (Press release). National Aeronautics and Space Administration. Retrieved 10 August 2019.
  30. ^ a b c Lauretta, D.S.; Bartels, A.E.; et al. (April 2015). "The OSIRIS-REx target asteroid (101955) Bennu: Constraints on its physical, geological, and dynamical nature from astronomical observations". Meteoritics & Planetary Science. 50 (4): 834–849. Bibcode:2015M&PS...50..834L. CiteSeerX 10.1.1.723.9955. doi:10.1111/maps.12353. S2CID 32777236.
  31. ^ Voosen P (2020). "NASA mission set to sample carbon-rich asteroid". Science. 370 (6513): 158. Bibcode:2020Sci...370..158V. doi:10.1126/science.370.6513.158. PMID 33033199. S2CID 222237648.
  32. ^ a b Kaplan, H. H.; Lauretta, D. S.; Simon, A. A.; Eno, H. L. (2020). "Bright carbonate veins on asteroid (101955) Bennu: Implications for aqueous alteration history". Science. 370 (6517): eabc3557. Bibcode:2020Sci...370.3557K. doi:10.1126/science.abc3557. PMID 33033155. S2CID 222236463.
  33. ^ a b c d Morton, Erin (19 March 2019). "NASA Mission Reveals Asteroid Has Big Surprises". AsteroidMission.org. Retrieved 19 March 2019.
  34. ^ Emery, J.; et al. (July 2014), Muinonen, K. (ed.), "Thermal infrared observations and thermophysical characterization of the OSIRIS-REx target asteroid (101955) Bennu", Conference Proceedings Asteroids, Comets, Meteors 2014: 148, Bibcode:2014acm..conf..148E.
  35. ^ Scheeres, D.J. (8 October 2020). "Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu". Science Advances. 6 (41): eabc3350. Bibcode:2020SciA....6.3350S. doi:10.1126/sciadv.abc3350. PMC 7544499. PMID 33033036.
  36. ^ Hergenrother, Carl W.; et al. (September 2013), "Lightcurve, Color and Phase Function Photometry of the OSIRIS-REx Target Asteroid (101955) Bennu", Icarus, 226 (1): 663–670, Bibcode:2013Icar..226..663H, doi:10.1016/j.icarus.2013.05.044.
  37. ^ King, A.; Solomon, J.; Schofield, P.; Russell, S. (December 2015). "Characterising the CI and CI-like carbonaceous chondrites using thermogravimetric analysis and infrared spectroscopy". Earth, Planets and Space. 67: 1989. Bibcode:2015EP&S...67..198K. doi:10.1186/s40623-015-0370-4. hdl:10141/622224.
  38. ^ Takir, D.; Emery, J.; Hibbits, C. (2017). 3-μm Spectroscopy of Water-Rich Meteorites and Asteroids: New Results and Implications. Hayabusa Symposium 2017.
  39. ^ Bates, H.; Hanna, K.; King, A.; Bowles, N. (2018). Thermal Infrared Spectra of Heated CM and C2 Chondrites and Implications for Asteroid Sample Return Missions (PDF). Hayabusa Symposium 2018.
  40. ^ a b Hamilton, V.; Simon, A.; Kaplan, H.; Christensen, P.; Reuter, D.; DellaGiustina, D.; Haberle, C.; Hanna, R.; Brucato, J.; Praet, A.; Glotch, T.; Rogers, A.; Connolly, H.; McCoy, T.; Emery, J.; Howell, E; Barucci, M.; Clark, B.; Lauretta, D. (March 2020). "OVIRS Results". VNIR and TIR spectral characteristics of (101955) Bennu from OSIRIS-REx Detailed Survey and Reconnaissance Observations (PDF). 51st LPSC.
  41. ^ Mason, B. (1962). Meteorites. New York and London: John Wiley and Sons, Inc. p. 60. OCLC 468300914. an important constituent in many of the carbonaceous chondrites
  42. ^ Takir, D.; Emery, J.; McSween, H.; Hibbits, C.; Clark, R.; Pearson, N.; Wang, A. (2013). "Nature and degree of aqueous alteration in CM and CI carbonaceous chondrites". Meteoritics & Planetary Science. 48 (9): 1618. Bibcode:2013M&PS...48.1618T. doi:10.1111/maps.12171. S2CID 129003587.
  43. ^ a b Bates, H.; King, A.; Donaldson-Hanna, K.; Bowles, N.; Russell, S. (19 November 2019). "Linking mineralogy and spectroscopy of highly aqueously altered CM and CI carbonaceous chondrites in preparation for primitive asteroid sample return". Meteoritics & Planetary Science. 55 (1): 77–101. doi:10.1111/maps.13411. hdl:10141/622636. observations of primitive, water‐rich asteroids
  44. ^ King, A.; Schofield, P.; Russell, S. (2017). "Type 1 aqueous alteration in CM carbonaceous chondrites: Implications for the evolution of water-rich asteroids". Meteoritics & Planetary Science. 52 (6): 1197. Bibcode:2017M&PS...52.1197K. doi:10.1111/maps.12872. hdl:10141/622203. small amounts of opaque phases (e.g., magnetite, Fe-sulfides) known to ...have a large effect on the overall spectral shape
  45. ^ Kerridge, J.; Mackay, A.; Boynton, W. (27 July 1979). "Magnetite in CI Carbonaceous Meteorites: Origin by Aqueous Activity on a Planetesimal Surface". Science. 205 (4404): 395–397. Bibcode:1979Sci...205..395K. doi:10.1126/science.205.4404.395. PMID 17790849. S2CID 9916605.
  46. ^ Brearley, A. (2006). "The Action of Water". Meteorites and the Early Solar System II. Tucson: University of Arizona Press. p. 587. ISBN 978-0-8165-2562-1.
  47. ^ a b Rubin, A.; Li, Y. (December 2019). "Formation and destruction of magnetite in CO3 chondrites and other chondrite groups". Geochemistry. 79 (4): article 125528. Bibcode:2019ChEG...79l5528R. doi:10.1016/j.chemer.2019.07.009. S2CID 201224827.
  48. ^ Yang, B.; Jewitt, D. (2010). "Identification of Magnetite in B-type asteroids". Astronomical Journal. 140 (3): 692. arXiv:1006.5110. Bibcode:2010AJ....140..692Y. doi:10.1088/0004-6256/140/3/692. S2CID 724871. evidence of water ice" "an important product of parent-body aqueous alteration
  49. ^ Kita, J.; Defouilloy, C.; Goodrich, C.; Zolensky, M. (2017). "O. isotope ratios of magnetite in CI-like clasts from a polymict ureilite" (PDF). Annual Meeting of the Meteoritical Society 2017 (LPI Contrib. No. 1987). ratios of magnetite are of special interest because...
  50. ^ Cloutis, E.; Hiroi, T.; Gaffey, M.; Alexander, C.; Mann, P. (2011). "Spectral Reflectance Properties of carbonaceous chondrites: 1. CI chondrites". Icarus. 212 (1): 180. Bibcode:2011Icar..212..180C. doi:10.1016/j.icarus.2010.12.009.
  51. ^ Clark, B.; Binzel, R.; Howell, E; Cloutis, E.; Ockert-Bell, M.; Christensen, P.; Barucci, M.; DeMeo, F.; Lauretta, D.; Connolly, H.; Soderberg, A.; Hergenrother, C.; Lim, L.; Emery, J.; Mueller, M. (2011). "Asteroid (101955) 1999 RQ36: Spectroscopy from 0.4 to 2.4 μm and meteorite analogs". Icarus. 216 (2): 462. Bibcode:2011Icar..216..462C. doi:10.1016/j.icarus.2011.08.021.
  52. ^ Miller, Katrina (22 March 2024). "Life After Asteroid Bennu – Dante Lauretta, the planetary scientist who led the OSIRIS-REx mission to retrieve a handful of space dust, discusses his next final frontier". The New York Times. Archived from the original on 22 March 2024. Retrieved 22 March 2024.
  53. ^ "NASA's latest asteroid target had a wet and wild history". 10 December 2018. Retrieved 19 September 2023.
  54. ^ "OSIRIS-REx Arrives at Bennu – 2018 AGU Press Conference". 10 December 2018. Retrieved 31 December 2020.
  55. ^ Stolte, D. (9 January 2014). "7 Questions for Dante Lauretta, Leader of UA's Biggest Space Mission". Retrieved 31 December 2020. We think Bennu is a water-rich asteroid
  56. ^ Lauretta, D. (25 September 2019). "OSIRIS-REx Explores Asteroid Bennu". Retrieved 31 December 2020. water-rich asteroid
  57. ^ All About Bennu: A Rubble Pile with a Lot of Surprises. Kimberly M.S. Cartier, EOS Planetary Sciences. 21 March 2019. "In terms of spectra and minerology, Bennu's rocks 'look a lot like the rarest, most fragile meteorites in our collection,' Lauretta said, referring to the CM carbonaceous chondrites"
  58. ^ a b Hamilton, V.E.; Simon, A.A. (2019). "Evidence for widespread hydrated minerals on asteroid (101955) Bennu". Nature Astronomy. 3 (4): 332–340. Bibcode:2019NatAs...3..332H. doi:10.1038/s41550-019-0722-2. hdl:1721.1/124501. PMC 6662227. PMID 31360777.
  59. ^ Lauretta, D. (4 April 2019). "The unexpected surface of asteroid (101955) Bennu". Nature. 568 (7750): 55–60. Bibcode:2019Natur.568...55L. doi:10.1038/s41586-019-1033-6. PMC 6557581. PMID 30890786. "This finding is in agreement with pre-encounter measurements and consistent with CI and CM chondrites."
  60. ^ "NASA's Newly Arrived OSIRIS-REx Spacecraft Already Discovers Water on Asteroid". NASA. 11 December 2018.
  61. ^ "Water found on asteroid, confirming Bennu as excellent mission target". Science Daily. 10 December 2018. Retrieved 10 December 2018.
  62. ^ Lauretta, D. (12 December 2018). "Welcome to Bennu Press Conference – First Mission Science Results". YouTube. Archived from the original on 15 December 2021. Retrieved 24 July 2019. "Report Card" at 25:15
  63. ^ Feierberg, M.; Lebofsky, L.; Tholen, D. (1985). "The nature of C-class asteroids from 3u spectrophotometry". Icarus. 63 (2): 191. Bibcode:1985Icar...63..183F. doi:10.1016/0019-1035(85)90002-8.
  64. ^ Sears, D. (2004). The Origin of Chondrules and Chondrites. Cambridge University Press. ISBN 978-1-107-40285-0.[page needed]
  65. ^ Russell, Sara S.; Ballentine, Chris J.; Grady, Monica M. (17 April 2017). "The origin, history and role of water in the evolution of the inner Solar System". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 375 (2094): 20170108. Bibcode:2017RSPTA.37570108R. doi:10.1098/rsta.2017.0108. PMC 5394259. PMID 28416731. Water in chondrites is contained within clay minerals, with H2O accounting for up to 10% weight percent...water is also stored in chondrites in direct liquid form as inclusions
  66. ^ Kaplan, H.; Hamilton, V.; Howell, E.; Anderson, S.; Barrucci, M.; Brucato, J.; Burbine, T.; Clark, B.; Cloutis, E.; Connolly, H.; Dotto, E.; Emery, J.; Fornasier, S.; Lantz, C.; Lim, L.; Merlin, F.; Praet, A.; Reuter, D.; Sandford, S.; Simon, A.; Takir, D.; Lauretta, D. (2020). "Visible-near infrared spectral indices for mapping mineralogy and chemistry with OSIRIS-REx". Meteoritics & Planetary Science. 55 (4): 744–765. Bibcode:2020M&PS...55..744K. doi:10.1111/maps.13461. S2CID 216247217.
  67. ^ Potin, S.; Beck, P.; Usui, F.; Bonal, L.; Vernazza, P.; Schmidtt, B. (September 2020). "Style and intensity of hydration among C-complex asteroids: A comparison to desiccated carbonaceous chondrites". Icarus. 348: article 113826. arXiv:2004.09872. Bibcode:2020Icar..34813826P. doi:10.1016/j.icarus.2020.113826. S2CID 216036128.
  68. ^ Praet, A.; Barucci, M.; Kaplan, H.; Merlin, F.; Clark, B.; Simon, A.; Hamilton, V.; Emery, J.; Howell, E.; Lim, L. (March 2020). Estimated hydration of Bennu's surface from OVIRS observations by the OSIRIS-REx mission. 51st LPSC. Bibcode:2020LPI....51.1058P.
  69. ^ Simon, A.A.; Kaplan, H.H.; Hamilton, V.E.; Lauretta, D.S.; Campins, H.; Emery, J.P.; Barucci, M.A.; DellaGiustina, D. N; Reuter D.C.; Sandford S.A.; Golish D.R.; Lim L.F.; Ryan A.; Rozitis B.; Bennett C.A. (8 October 2020). "Widespread carbon-bearing materials on near-Earth asteroid (101955) Bennu" (PDF). Science. 370 (6517): eabc3522. Bibcode:2020Sci...370.3522S. doi:10.1126/science.abc3522. PMID 33033153. S2CID 222236203. water-rich, similar to the CM class of chondrites
  70. ^ a b c d Nuth, III, J.; Abreu, N.; Ferguson, F.; Glavin, D.; Hergenrother, C.; Hill, H.; Johnson, N.; Pajola, M.; Walsh, K. (December 2020). "Volatile-rich Asteroids in the Inner Solar System". Planetary Science Journal. 1 (3): 82. Bibcode:2020PSJ.....1...82N. doi:10.3847/PSJ/abc26a.
  71. ^ Osinski, G. "Feasibility Of Mining Bennu". Retrieved 22 August 2023.
  72. ^ Kurokawa, H.; Shibuya, T.; Sekine, Y.; Ehlmann, B.L.; Usui, F.; Kikuchi, S.; Yoda, M. (January 2022). "Distant Formation and Differentiation of Outer Main Belt Asteroids and Carbonaceous Chondrite Parent Bodies". AGU Advances. 3 (1). arXiv:2112.10284. Bibcode:2022AGUA....300568K. doi:10.1029/2021AV000568. S2CID 245302669.
  73. ^ Montoya, M.; Plummer, J.; Martinez, S. III; Snead, C.J.; Lunning, N.; Righter, K.; Allums, K.; Rodriguez, M.; Funk, R.C.; Connelly, W.; Gonzalez, C.; Calva, C.; Ferrodous, J.; Lugo, G.; Hernandez Gomez, N.; Connolly, H.C. Jr. (2023). Materials-Compliant Containers in Preparation for OSIRIS-REx Sample Return. 86th Meteoritical Society Meeting. p. 6050.
  74. ^ Prince, B.S.; Zega, T.J.; Connolly, H.C. Jr.; Lauretta, D.S. (2023). Developing Fluid Inclusion Analysis Techniques in Anticipation of OSIRIS-REx Sample Return. 86th MetSoc. p. 6155.
  75. ^ Bonato, E.; Helbert, J.; Schwinger, S.; Maturilli, A.; Greshake, A.; Hecht, L. (2023). The Sample Analysis Laboratory At DLR And Its Extension To Curation Facility for MMX. 86th MetSoc. p. 6035.
  76. ^ Connolly, H.; Jawin, E.; Ballouz, R.; Walsh, K.; McCoy, T.; Dellagiustina, D. (2019). OSIRIS-REx sample science and the geology of active asteroid Bennu. 82nd Meteoritical Society Meeting. p. 2157. Bibcode:2019LPICo2157.6209C.
  77. ^ Lim, L. (2019). OSIRIS-REx update. 21st NASA Small Bodies Assessment Group. "Bennu is an Active Asteroid!"
  78. ^ a b Barrucci, M.; Michel, P. (September 2019). Asteroid-Comet continuum: no doubt but many questions. 2019 EPSC-DPS conference. pp. 202–1.
  79. ^ Hergenrother, C.; Adam, C.; Antreasian, P.; Al Asad, M.; Balram-Knutson, S. (September 2019). (101955) Bennu is an active asteroid. 2019 EPSC-DPS conference. pp. 852–1.
  80. ^ "Feb 11, 2019". Retrieved 15 November 2019.
  81. ^ Hergenrother, C.; Maleszweski, C.; Nolan, C.; Li, J.; Drouet D'aubigny, C. (19 March 2019). "The Operational Environment and Rotational Acceleration of Asteroid (101955) Bennu from OSIRIS-REx Observations". Nature Communications. 10 (1): 1291. Bibcode:2019NatCo..10.1291H. doi:10.1038/s41467-019-09213-x. PMC 6425024. PMID 30890725.
  82. ^ No One Knows Why Rocks Are Exploding From Asteroid Bennu. Daniel Oberhaus, Wired. 5 December 2019.
  83. ^ a b c Lauretta, D.S.; Hergenrother, C.W.; Chesley, S.R.; Leonard, J.M.; Pelgrift, J.Y.; et al. (6 December 2019). "Episodes of particle ejection from the surface of the active asteroid (101955) Bennu" (PDF). Science. 366 (6470): eaay3544. Bibcode:2019Sci...366.3544L. doi:10.1126/science.aay3544. PMID 31806784. S2CID 208764910..
  84. ^ "Definitions of terms in meteor astronomy" (PDF). Retrieved 31 July 2020.
  85. ^ Grun, E.; Krüger, H.; Srama, R. (2019). "The Dawn of Dust Astronomy". Space Science Reviews. 215 (7): 46. arXiv:1912.00707. Bibcode:2019SSRv..215...46G. doi:10.1007/s11214-019-0610-1. S2CID 208527737. 3. Multifaceted Scientific Dust Observations
  86. ^ Boe, B.; Jedicke, R.; Wiegert, P.; Meech, K.; Morbidelli, A. (September 2019). Distinguishing Between Solar System Formation Models with Manxes (or not). 2019 EPSC-DPS conference. pp. 626–2.[page needed]
  87. ^ Gounelle, M. (2012). The Asteroid-Comet Continuum: Evidence from Extraterrestrial Samples. 2012 European Planetary Science Congress. p. 220.
  88. ^ Rickman, H. (2018). Origin and Evolution of Comets: Ten Years after the Nice Model, One Year after Rosetta. Singapore: World Scientific. pp. 162–168. Sec. 4.3 Dormancy and Rejuvenation
  89. ^ Nuth, J.; Johnson, N.; Abreu, N. (March 2019). Are B-type Asteroids Dormant Comets? (PDF). 50th LPSC. p. 2132.
  90. ^ Schroder, S.; Poch, I.; Ferrari, M.; De Angelis, S.; Sultana, R. (September 2019). Experimental evidence for the nature of Ceres blue material (PDF). 2019 EPSC-DPS conference. Epsc-DPS Joint Meeting 2019. Vol. 2019. pp. EPSC–DPS2019–78. Bibcode:2019EPSC...13...78S.
  91. ^ Marsset, M.; DeMeo, F.; Polishook, D.; Binzel, R. (September 2019). Near-infrared spectral variability on the newly active asteroid (6478) Gault. 2019 EPSC-DPS conference. Epsc-DPS Joint Meeting 2019. Vol. 2019. pp. EPSC-DPS2019-280. Bibcode:2019EPSC...13..280M.
  92. ^ Fukai, R.; Arakawa, S. (2021). "Assessment of Cr isotopic heterogeneities of volatile-rich asteroids based on multiple planet formation models". The Astrophysical Journal. 908 (1): 64. arXiv:2012.05467. Bibcode:2021ApJ...908...64F. doi:10.3847/1538-4357/abd2b9. S2CID 228084040.
  93. ^ Miura, H.; Nakamura, E.; Kunihiro, T. (2022). "The Asteroid 162173 Ryugu: a Cometary Origin". The Astrophysical Journal Letters. 925 (2): 15. Bibcode:2022ApJ...925L..15M. doi:10.3847/2041-8213/ac4bd5.
  94. ^ Bauer, G. (2019). Active Asteroids (PDF). 21st NASA Small Bodies Assessment Group.
  95. ^ Chang, Kenneth; Stirone, Shannon (19 March 2019). "The Asteroid Was Shooting Rocks Into Space. 'Were We Safe in Orbit?' – NASA's Osiris-Rex and Japan's Hayabusa2 spacecraft reached the space rocks they are surveying last year, and scientists from both teams announced early findings on Tuesday (03/19/2019)". The New York Times. Retrieved 21 March 2019.
  96. ^ "Asteroid's Features to be Named After Mythical Birds". 8 August 2019.
  97. ^ Davis, Jason (15 August 2019). "OSIRIS-REx Team Picks 4 Candidate Sample Sites on Asteroid Bennu". The Planetary Society. Retrieved 24 May 2021.
  98. ^ "First Official Names Given to Features on Asteroid Bennu". AsteroidMission.org. NASA. 6 March 2020. Retrieved 6 May 2020.
  99. ^ Shekhtman, Svetlana (6 July 2022). "NASA Reveals Surface of Asteroid Bennu is Like Plastic Ball Pit". NASA. Retrieved 4 November 2022. Public Domain This article incorporates text from this source, which is in the public domain.
  100. ^ Steigerwald, Bill (30 June 2022). "Some Asteroids 'Aged Early' by Sun, NASA Finds". NASA. Retrieved 4 November 2022. Public Domain This article incorporates text from this source, which is in the public domain.
  101. ^ "Candidate Sample Sites". AsteroidMission.org. NASA. Retrieved 2 January 2019.
  102. ^ a b c "X Marks the Spot: Sample Site Nightingale Targeted for Touchdown" (Press release). AsteroidMission.org. NASA. 12 December 2019. Retrieved 28 December 2019.
  103. ^ "Bennu". Gazetteer of Planetary Nomenclature. International Astronomical Union. Archived from the original on 7 May 2020. Retrieved 6 May 2020.
  104. ^ Bensby, T.; Feltzing, S. (2006). "The origin and chemical evolution of carbon in the Galactic thin and thick discs" (PDF). Monthly Notices of the Royal Astronomical Society. 367 (3): 1181–1193. arXiv:astro-ph/0601130. Bibcode:2006MNRAS.367.1181B. doi:10.1111/j.1365-2966.2006.10037.x. S2CID 7771039.
  105. ^ Michel, P.; Ballouz, R.-L.; Barnouin, O.S.; Jutzi, M.; Walsh, K.J.; May, B.H.; Manzoni, C.; Richardson, D.C.; Schwartz, S.R.; Sugita, S.; Watanabe, S. (27 May 2020). "Collisional formation of top-shaped asteroids and implications for the origins of Ryugu and Bennu". Nature Communications. 11 (1): 2655. Bibcode:2020NatCo..11.2655M. doi:10.1038/s41467-020-16433-z. ISSN 2041-1723. PMC 7253434. PMID 32461569.
  106. ^ Bottke, William F.; et al. (February 2015), "In search of the source of asteroid (101955) Bennu: Applications of the stochastic YORP model", Icarus, 247: 191–217, Bibcode:2015Icar..247..191B, doi:10.1016/j.icarus.2014.09.046.
  107. ^ Ballouz, R.; Walsh, K. J.; Barnouin, O. S.; Lauretta, D. S. (2020). "Bennu's near-Earth lifetime of 1.75 million years inferred from craters on its boulders" (PDF). Nature. 5 (587): 205–209. Bibcode:2020Natur.587..205B. doi:10.1038/s41586-020-2846-z. PMID 33106686. S2CID 225082141.
  108. ^ a b Lauretta, D. S.; et al. (April 2015), "The OSIRIS-REx target asteroid (101955) Bennu: Constraints on its physical, geological, and dynamical nature from astronomical observations", Meteoritics & Planetary Science, 50 (4): 834–849, Bibcode:2015M&PS...50..834L, CiteSeerX 10.1.1.723.9955, doi:10.1111/maps.12353, S2CID 32777236.
  109. ^ Hergenrother, C. (12 December 2013). "The Strange Life of Asteroid Phaethon – Source of the Geminid Meteors". Dslauretta: Life on the Asteroid Frontier. Archived from the original on 24 March 2019. Retrieved 25 July 2019.
  110. ^ Maltagliati, L. (24 September 2018). "Cometary Bennu?". Nature Astronomy. 2 (10): 761. Bibcode:2018NatAs...2..761M. doi:10.1038/s41550-018-0599-5. S2CID 189930305.
  111. ^ a b "Horizons Bennu Orbital Elements for 2135-Aug-30 and 2135-Sep-30" (PR is orbital period in days). JPL Horizons. Retrieved 19 August 2021.
  112. ^ "Horizons Batch for Bennu MaxDistance 2045". JPL Horizons. Retrieved 22 August 2021.
  113. ^ Gravity Simulator Solution for Sept 2182 by Tony Dunn
  114. ^ "Bennu 2135/2182 orbits" (Nominal and impacting solution for 2182). NASA Scientific Visualization Studio. 11 August 2021. Retrieved 20 August 2021.
  115. ^ a b "(101955) Bennu Ephemerides for 24 September 2182". NEODyS (Near Earth Objects – Dynamic Site). Archived from the original on 14 August 2021. Retrieved 14 August 2021.
  116. ^ Robert Marcus; H. Jay Melosh & Gareth Collins (2010). "Earth Impact Effects Program". Imperial College London / Purdue University. Retrieved 7 February 2013. (solution using density of 2,600 kg/m^3, sped of 17km/s, and impact angle of 45 degrees)
  117. ^ Milani, Andrea; Chesley, Steven R.; Sansaturio, Maria Eugenia; Bernardi, Fabrizio; Valsecchi, Giovanni B.; Arratia, Oscar (2009). "Long term impact risk for (101955) 1999 RQ36". Icarus. 203 (2): 460–471. arXiv:0901.3631. Bibcode:2009Icar..203..460M. doi:10.1016/j.icarus.2009.05.029. S2CID 54594575.
  118. ^ Chesley, Steven R.; Farnocchia, Davide; Nolan, Michael C.; Vokrouhlický, David; Chodas, Paul W.; Milani, Andrea; Spoto, Federica; Rozitis, Benjamin; Benner, Lance A.M.; Bottke, William F.; Busch, Michael W.; Emery, Joshua P.; Howell, Ellen S.; Lauretta, Dante S.; Margot, Jean-Luc; Taylor, Patrick A. (2014). "Orbit and bulk density of the OSIRIS-REx target Asteroid (101955) Bennu". Icarus. 235: 5–22. arXiv:1402.5573. Bibcode:2014Icar..235....5C. doi:10.1016/j.icarus.2014.02.020. ISSN 0019-1035. S2CID 30979660.
  119. ^ "Sandia supercomputers offer new explanation of Tunguska disaster". Sandia National Laboratories. 17 December 2007. Archived from the original on 19 February 2013. Retrieved 22 December 2007.
  120. ^ Wheeler, Lorien F.; Mathias, Donovan L. (2019). "Probabilistic assessment of Tunguska-scale asteroid impacts". Icarus. 327: 83–96. Bibcode:2019Icar..327...83W. doi:10.1016/j.icarus.2018.12.017.
  121. ^ "(101955) Bennu Ephemerides for September 2060". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 15 May 2019.
  122. ^ Paul Chodas (24 March 2018). "Recent Bennu Press Stories Need Correction". Center for NEO Studies (CNEOS).
  123. ^ a b Table 3. Impact dates, keyhole centers and widths in the 2135 B-plane (Farnocchia2021) The table reports the zeta coordinate on the B-plane, which is not the same thing as the miss distance during the 2135 encounter.
  124. ^ a b Ye, Quanzhi (2019). "Prediction of Meteor Activities from (101955) Bennu" (PDF). American Astronomical Society. 3 (3): 56. Bibcode:2019RNAAS...3...56Y. doi:10.3847/2515-5172/ab12e7. S2CID 187247696.
  125. ^ Wall, Mike (10 December 2018). "Asteroid Bennu Had Water! NASA Probe Makes Tantalizing Find". Space.com. Retrieved 6 January 2019.
  126. ^ "Touching the Asteroid" (video, 54:03 min.), Nova on PBS, 21 October 2020. Retrieved 20-10-22.
  127. ^ "NASA's OSIRIS-REx Completes Final Tour of Asteroid Bennu". NASA. 7 April 2021. Retrieved 10 May 2021.
  128. ^ "NASA to Launch New Science Mission to Asteroid in 2016". NASA. 25 May 2011. Retrieved 21 May 2013.
  129. ^ Chang, Kenneth (11 October 2023). "NASA Unveils First Glimpse of 'Scientific Treasure' Collected From Asteroid – Scientists said they got more material than expected from the Osiris-Rex mission during its seven-year journey to the asteroid Bennu". The New York Times. Archived from the original on 11 October 2023. Retrieved 12 October 2023.
  130. ^ Kuthunur, Sharmila (13 December 2023). "'What is that material?': Potentially hazardous asteroid Bennu stumps scientists with its odd makeup – Scientists found signs of organic molecules in the first samples of potentially hazardous asteroid Bennu, as well as a 'head scratching' material that has yet to be identified". LiveScience. Archived from the original on 14 December 2023. Retrieved 13 December 2023.
  131. ^ Rabie, Passant (15 December 2023). "It's Been 2 Months. Why Can't NASA Open the Asteroid Sample Container? – The space agency is having to develop new tools to crack open the canister containing bits from asteroid Bennu". Gizmodo. Archived from the original on 15 December 2023. Retrieved 16 December 2023.
  132. ^ Barry, Rachel Ann (11 January 2024). "NASA's OSIRIS-REx Team Clears Hurdle to Access Remaining Bennu Sample". OSIRIS-REx Mission. NASA.
  133. ^ MacDonald, Cheyenne (13 January 2024). "NASA finally got the stuck lid off its asteroid Bennu sample container – Thanks to some stubborn fasteners, the agency spent three months locked out of the sample OSIRIS-REx dropped off". Engadget. Archived from the original on 14 January 2024. Retrieved 13 January 2024.
  134. ^ Rabie, Passant (22 January 2024). "NASA Finally Opened the Asteroid Container and Holy Crap That's a Lot of Asteroid – After months of struggling to get to the bulk of the OSIRIS-REx asteroid sample, the space agency has unveiled a treasure trove of ancient rocks and dust". Gizmodo. Archived from the original on 23 January 2024. Retrieved 22 January 2024.
  135. ^ Rabie, Passant (15 February 2024). "We Finally Know How Much of That Asteroid OSIRIS-REx Grabbed in Space – Engineers struggled to open the sample canister for months, but it was all worth it for twice the amount of asteroid they thought they were getting". Gizmodo. Archived from the original on 16 February 2024. Retrieved 16 February 2024.
  136. ^ Near-Earth Asteroid Delta-V for Space Rendezvous
  137. ^ a b "Why Bennu?". OSIRIS-REx Mission. Arizona Board of Regents. Retrieved 10 September 2016.
  138. ^ a b c d e Lauretta, Dante S.; et al. (26 June 2024). "Asteroid (101955) Bennu in the laboratory: Properties of the sample collected by OSIRIS-REx". Meteoritics & Planetary Science. 59 (9): 2453–2486. doi:10.1111/maps.14227.
  139. ^ Pearlman, Robert Z. (3 November 2023). "Smithsonian debuts 1st display of asteroid Bennu sample brought back by OSIRIS-REx". space.com. Retrieved 6 November 2023.
  140. ^ @NASAExhibit (15 October 2024). "NASA exhibit at IAC 2024 opens with Bennu sample" (Tweet). Retrieved 24 October 2024 – via Twitter.
  141. ^ @NASAExhibit (18 October 2024). "NASA invites the general public to view a Bennu sample at their booth for the IAC 2024 public day" (Tweet). Retrieved 24 October 2024 – via Twitter.
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