(162173) Ryugu

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Asteroid
(162173) Ryugu
Animation composed of recordings from the Japanese probe Hayabusa 2
Animation composed of recordings from the Japanese probe Hayabusa 2
Properties of the orbit ( animation )
Epoch:  December 9, 2014 ( JD 2,457,000.5)
Orbit type Apollo type
Major semi-axis 1.1895  AU
eccentricity 0.1903
Perihelion - aphelion 0.96319 AU - 1.41582 AU
Inclination of the orbit plane 5.8839 °
Length of the ascending node 251.6117 °
Argument of the periapsis 211.4257 °
Sidereal period 473.87 d
Physical Properties
Medium diameter 0.9 km
Albedo 0.07
Medium density 1.19 g / cm³
Rotation period 7.63 h
Absolute brightness 19,173 likes
Spectral class C (Tholen) / Cg (SMASSII)
history
Explorer LINEAR
Date of discovery May 10, 1999
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . The affiliation to an asteroid family is automatically determined from the AstDyS-2 database . Please also note the note on asteroid items.
Orbit of the asteroid Ryugu

(162173) Ryugu (also: 1999 JU3, of Japanese 竜宮 Ryugu , German , Dragon Palace ' ) is an asteroid of the Apollo-type , which on 10 May 1999 under the LINEAR project was discovered. The asteroid is observed by the Arecibo Observatory and the Goldstone Deep Space Communications Complex , among others .

Physical data

Ryugu measures about a kilometer in diameter, its mass is about half a billion tons. The C-type asteroid ("C" for carbon-rich) resembles the 4.5 billion year old carbonaceous chondrites in meteorite collections , which are not exposed to higher temperatures and are thus little changed . The average density is only 1.19 ± 0.02 grams per cubic centimeter, which means that a large part of the asteroid must be riddled with cavities.

Orbit

Ryugu orbits the sun within 473.9 days at a distance of 0.96  AU to 1.42 AU, ie "crosses" the orbit of the earth and approaches the orbit of Mars. The smallest distance between the asteroid orbit (Earth MOID) is around 150,000 km.

construction

Replica of the surface of Ryugu in the Japanese exhibition "Kuroi Sho-Wakusei - Ryugu"

The mean density of Ryugu shows that the asteroid consists of numerous small "chunks" ( rubble pile ). From the size of the crater created by a 2.5 kg projectile from the Hayabusa 2 probe, it was concluded that the asteroid was not held together by cohesion , but only by gravitational force .

On photos taken by MASCOT , which the lander took himself during the descent and when he arrived on the surface, “mainly dark, decimeter to meter-sized, angular, but sometimes also smooth, boulders can be seen. Boulders with smooth fracture surfaces and sharp edges are a bit lighter than rocks with a more irregular, cauliflower-like and sometimes crumbly surface. […] The two types of rock observed are distributed in roughly equal parts on the surface on Ryugu. ”Surprisingly, there was not as much fine dust on the surface, ie regolith formed by space weathering , as expected.

Before the arrival of the Hayabusa 2 probe, the shape of the asteroid was initially estimated to be “rather rounded”. The first pictures taken during the arrival of the mission show his shape as "surprisingly sharp-edged" and octahedron-shaped with a clearly pronounced thickening at the equator. It is speculated that the asteroid used to rotate faster and that centrifugal force moved material from the poles to the equator.

History of origin

The asteroid originally stems from the asteroid belt between Mars and Jupiter and is likely to have formed when larger bodies collided, as the debris collected through mutual attraction and formed a new asteroid. Ryugu is similar to the asteroid (101955) Bennu , so it is likely that both are from the same asteroid family .

exploration

Exploration from Earth

"In addition, measurements from Earth show that the asteroid's rock may have come into contact with water."

- Ralf Jaumann , DLR planetary researcher and scientific spokesman for the experiments on the MASCOT lander, October 2012

With the help of astrospectroscopy , Ryugu was analyzed and assigned to the rare spectral class Cg of carbonaceous chondrites according to the SMASSII classification . The 0.7 μm absorption line , which shows water-containing phyllosilicates , was measured once, but further investigations have not been able to show this absorption line. The measurements on site with the AMICA camera (Asteroid Multi-band Imaging Camera) and the corresponding filter confirmed the absence of this absorption line.

Hayabusa-2 mission

(162173) Ryugu was selected as the primary target for the Japan Aerospace Exploration Agency's (JAXA) Hayabusa-2 mission, launched on December 3, 2014 . When Marco Polo mission of the ESA as part of its Cosmic Vision program, he is also among the possible targets.

In 2015, JAXA announced a public competition to find a name for the asteroid. On September 28, 2015 it was named after the underwater palace of the dragon god Ryūjin from a Japanese legend. The fisherman Urashima Taro visited this palace and brought back a black box with secrets. By analogy, Hayabusa 2 will visit the asteroid and bring back a capsule with rock samples.

Measurements and photos by the probe and their evaluation

First measurements showed a surface temperature of 30 to 100 ° C.

The Hayabusa 2 probe repeatedly came close to the surface and took high-resolution photos, for example a photo was taken from a height of only 64 meters on September 21, 2018, whereby the surface of a rock several meters in size can also be seen in detail. What is striking here is that the surface is free of regolith. In another recording, Sugita et al. deposits of regolith in depressions on the surface of a boulder about 20 meters in size.

T. Morota et al. investigated the spatial distribution of dark red and gray dust on the surface using cameras (ONC-W1 and ONC-T) and recognized that the dark red dust was created from the gray dust by solar warming (or space weather ). The dark red dust is currently mainly in the areas between the two poles and the equator. The authors explain this in such a way that the asteroid Ryugu received an entire surface 10 centimeters to 1 meter thick layer of dark red dust around 9 million years ago and since then, superficial, dark red dust has migrated away from the equator towards the poles. The color can also be used to chronologically classify the formation of craters with predominantly gray dust.

Based on spectroscopic data from the AMICA camera, Sugita et al. Ryugu according to the SMASSII classification as a Cb asteroid. Furthermore, they name the asteroid families Eulalia and Polana as possible origins of Ryugu. Due to the large impact craters (e.g. Urashima and Kolobok: 290 m and 240 m in diameter) Sugita et al. suggests that the asteroid was in the asteroid belt 10 million to 100 million years ago and only then entered its new orbit. Less than 1 million years ago, Ryugu must have been superficially transformed, as evidenced by the small impact craters with a diameter of about 10 meters.

Taking the soil samples

The Hayabusa 2 spacecraft brings soil samples to Earth that are expected to arrive in Australia with a landing capsule at the end of 2020. Two samples were taken at spatially adjacent locations. The first on February 22, 2019 (Japanese time). The space probe was steered to the surface and when the sampler came into contact with the surface, a 5 gram tantalum projectile was fired from inside the sampler . The resulting material was captured. When taking the second sample, on April 5, 2019, the space probe fired a two-kilogram, flat copper disc at the surface that was deformed by the acceleration, and on July 11, 2019, the sampler took fresh soil material from the crater created in this way was not subject to space weathering.

In principle, various material samples can be taken with the sampler : On the one hand, solid material that is exposed and then gas - including noble gases - can be captured in gas-tight chambers. Regardless of the triggering of the tantalum projectile, grains of 1 mm to 5 mm in size can be picked up where the sampler touches the surface of Ryugu with the help of a purely mechanical device.

See also

Web links

Commons : (162173) Ryugu  - collection of pictures, videos and audio files

Individual evidence

  1. ^ A b S. Tachibana, M. Abe, M. Arakawa, M. Fujimoto, Y. Iijima: Hayabusa2: Scientific importance of samples returned from C-type near-Earth asteroid (162173) 1999 JU3 . In: GEOCHEMICAL JOURNAL . tape 48 , no. 6 , 2014, ISSN  0016-7002 , p. 573-574 , doi : 10.2343 / geochemj.2.0350 ( jst.go.jp [accessed September 14, 2019]).
  2. ↑ リ ュ ウ グ ウ を 下 見 す る？ （そ の ４ . In: hayabusa2.JAXA.jp. Japan Aerospace Exploration Agency , accessed June 27, 2018 (Japanese).
  3. ↑ a b Near-Earth asteroid Ryugu: a fragile cosmic 'pile of rubble'. In: dlr.de. German Aerospace Center , August 22, 2019, accessed on August 31, 2019 .
  4. ↑ 162173 Ryugu. In: neo.ssa.ESA.int. European Space Agency , August 20, 2019, accessed August 31, 2019 .
  5. ^ M. Arakawa et al.: An artificial impact on the asteroid 162173 Ryugu formed a crater in the gravity-dominated regime . In: Science . March 19, 2020, ISSN  0036-8075 , p. eaaz1701 , doi : 10.1126 / science.aaz1701 ( sciencemag.org [accessed March 21, 2020]).
  6. ↑ Tilmann Althaus: Hayabusa-2 explores the dragon castle. In: Spektrum.de. Spectrum of Science , August 7, 2018, accessed August 18, 2018 .
  7. ↑ MASCOT: Asteroid Lander with a Sense of Orientation. In: DLR.de. German Aerospace Center, October 1, 2012, accessed on June 29, 2018 .
  8. ^ A b c S. Sugita, R. Honda, T. Morota, S. Kameda, H. Sawada: The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes . In: Science . March 19, 2019, ISSN  0036-8075 , p. eaaw0422 , doi : 10.1126 / science.aaw0422 ( researchgate.net [accessed September 16, 2019]).
  9. ↑ Martin Holland: German-Japanese asteroid mission Hayabusa2 started. In: heise.de . December 3, 2014, accessed December 3, 2014 .
  10. ↑ Tilmann Althaus: Give the asteroid 1999 JU3 a name! In: Spektrum.de. Spectrum of Science, July 22, 2015, accessed August 16, 2015 .
  11. ↑ Probe finds asteroid's surface is 30–100 degrees C. (No longer available online.) In: newsonjapan.com. July 20, 2018, archived from the original on February 27, 2019 ; accessed on August 31, 2019 .
  12. ↑ Ryugu surface imaged at highest resolution so far. In: hayabusa2.JAXA.jp. Japan Aerospace Exploration Agency, September 27, 2018, accessed September 14, 2019 (English, with photos).
  13. ^ S. Sugita, R. Honda, T. Morota, S. Kameda: High-resolution imaging and dynamic response observations of asteroid Ryugu. (PDF) Retrieved September 16, 2019 (English, PDF; 0.5 MB).
  14. ↑ T. Morota, S. Sugita, Y. Cho, M. Kanamaru, E. Tatsumi: Sample collection from asteroid (162173) Ryugu by Hayabusa2: Implications for surface evolution . In: Science . tape 368 , no. 6491 , May 8, 2020, ISSN  0036-8075 , p. 654–659 , doi : 10.1126 / science.aaz6306 ( sciencemag.org [accessed May 31, 2020]).
  15. ^ S. Sugita, R. Honda, T. Morota, S. Kameda, H. Sawada: The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes . In: Science . March 19, 2019, ISSN  0036-8075 , p. eaaw0422 , doi : 10.1126 / science.aaw0422 ( sciencemag.org [accessed September 22, 2019]).
  16. ↑ 2nd touchdown image bulletin. In: hayabusa2.JAXA.jp. Japan Aerospace Exploration Agency, July 11, 2019, accessed September 14, 2019 (English, with photos).
  17. ↑ Images from the 2nd touchdown. In: hayabusa2.JAXA.jp. Japan Aerospace Exploration Agency, July 26, 2019, accessed September 14, 2019 (with photos and video before and after the touchdown).