Images from the surface of asteroid Ryugu show rocks similar to carbonaceous chondrite meteorites

Jaumann, R.; Schmitz, Nicole; Ho, Tra‐Mi; Schröder, Stefan; Otto, Katharina A.; Stephan, K.; Elgner, S.; Krohn, Katrin; Preusker, Frank; Scholten, F.; Biele, Jens; Ulamec, Stephan; Krause, Christian; Sugita, Seiji; Matz, K. D.; Roatsch, Thomas; Parekh, Rutu; Mottola, S.; Grott, M.; Michel, Patrick; Trauthan, Frank; Koncz, Alexander; Michaelis, H.; Lange, Caroline; Grundmann, J. T.; Maibaum, Michael; Sasaki, Kaname; Wolff, Friederike; Reill, Josef; Moussi‐Soffys, Aurélie; Lorda, Laurence; Neumann, Wladimir; Vincent, Jean‐Baptiste; Wagner, Roland; Bibring, Jean‐Pierre; Kameda, Shingo; Yano, Hajime; Watanabe, Sei‐ichiro; Yoshikawa, Makoto; Tsuda, Yuichi; Okada, Tatsuaki; Yoshimitsu, Tetsuo; Mimasu, Yuya; Saiki, Takanao; Yabuta, Hikaru; Rauer, H.; Honda, Rie; Morota, T.; Yokota, Yasuhiro; Kouyama, T.

doi:10.1126/science.aaw8627

Cited by 110 publications

(74 citation statements)

References 38 publications

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“…Either fine regolith material is not being produced by processes such as thermal fracturing (Molaro et al, 2020, this collection) or fine material is being removed after formation by electrostatic lofting (Hartzell & Scheeres, 2013) or some other process. A scarcity of small particles sizes was found on Ryugu (Jaumann et al, 2019) which is a similar sized carbonaceous asteroid to Bennu and may also experience a depletion phenomenon.…”

Section: Resultsmentioning

confidence: 99%

Photometry of Particles Ejected From Active Asteroid (101955) Bennu

Hergenrother

Maleszewski

et al. 2020

JGR Planets

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Near‐Earth asteroid (101955) Bennu is an active asteroid experiencing mass loss in the form of ejection events emitting up to hundreds of millimeter‐ to centimeter‐scale particles. The close proximity of the Origins, Spectral Interpretations, Resource Identification, and Security–Regolith Explorer spacecraft enabled monitoring of particles for a 10‐month period encompassing Bennu's perihelion and aphelion. We found 18 multiparticle ejection events, with masses ranging from near zero to hundreds of grams (or thousands with uncertainties) and translational kinetic energies ranging from near zero to tens of millijoules (or hundreds with uncertainties). We estimate that Bennu ejects ~104 g per orbit. The largest event took place on 6 January 2019 and consisted of ~200 particles. The observed mass and translational kinetic energy of the event were between 459 and 528 g and 62 and 77 mJ, respectively. Hundreds of particles not associated with the multiparticle ejections were also observed. Photometry of the best‐observed particles, measured at phase angles between ~70° and 120°, was used to derive a linear phase coefficient of 0.013 ± 0.005 magnitudes per degree of phase angle. Ground‐based data back to 1999 show no evidence of past activity for Bennu; however, the currently observed activity is orders of magnitude lower than observed at other active asteroids and too low be observed remotely. There appears to be a gentle decrease in activity with distance from the Sun, suggestive of ejection processes such as meteoroid impacts and thermal fracturing, although observational bias may be a factor.

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Section: Resultsmentioning

confidence: 99%

Photometry of Particles Ejected From Active Asteroid (101955) Bennu

Hergenrother

Maleszewski

et al. 2020

JGR Planets

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“…The closest match from Hayabusa2 near‐infrared observations is with heated Ivuna (CI1) meteorite (Kitazato et al, ). MASCOT camera, on the other hand, revealed morphology features, like abundance of calcium‐aluminum‐rich inclusions, comparable to CV or CM meteorites (Jaumann et al, ).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties of Asteroid (162173) Ryugu

et al. 2020

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Observations of the magnetization state of asteroids indicate diverse properties. Values between 1.9 × 10 −6 Am 2 /kg (Eros) and 10 −2 Am 2 /kg (Braille) have been reported. A more detailed understanding of asteroidal magnetic properties allows far-reaching conclusions of the magnetization mechanism as well as the strength of the magnetic field of the solar system regions the asteroid formed in. The Hayabusa2 mission with its lander Mobile Asteroid Surface Scout is equipped with a magnetometer experiment, MasMag. MasMag is a state-of-the-art three-axis fluxgate magnetometer, successfully operated also on Philae, the Rosetta mission lander. MasMag has enabled, after Eros for the second time ever, to determine the magnetic field of an asteroid during descent and on-surface operations. The new observations show that Ryugu, a low-albedo C-type asteroid, has no detectable global magnetization, and any local magnetization is either small (< 10 −6 Am 2 /kg) or on very small (subcentimeter) scales. This implies, for example, that energetic solar wind particles could reach and alter the surface unimpeded by strong asteroidal magnetic fields, such as minimagnetospheres in case of the Moon.Plain Language Summary Magnetic measurements in space near and on solar system bodies such as asteroids can provide important information about their formation history and their material properties. Hayabusa2, a Japanese mission, visited asteroid Ryugu, a type of asteroid (carbon rich) not visited before. Ryugu is a rubble pile, that is, an agglomeration of rocks and boulders. It is not expected to have any global magnetic field, but it can be magnetized on smaller scales (boulders or pebbles). Hayabusa2 carried therefore a small lander called Mobile Asteroid Surface Scout equipped also with an instrument for magnetic field measurement (magnetometer). In this study, we present observations from the magnetometer that were collected during Mobile Asteroid Surface Scout's descent and landing on the surface of Ryugu. The magnetic measurements show that Ryugu is not magnetized on boulder (greater than centimeter) scales. This gives us indication on its origin and evolution. In particular, it shows that Ryugu and the bodies it was created from did not possess any magnetic field generation mechanism and that they were not created in an environment with strong background magnetic field. The results are important inputs for theories about the solar system evolution that work with magnetic field as one of the drivers for dust accretion and planetary formation.

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“…Close-up thermal images show the surface physical state and a variety of boulders at centimeter scale. As was seen by optical navigation cameras and the surface landers, it was evident that the surface of Ryugu is widely covered with several centimeter-to meter-sized rocks and boulders, but not with fine regolith [20,27,28]. The surroundings in the global and local thermal images correspond to the rough surface terrains that are covered with boulders down to the tens-of-centimeter scale in the close-up thermal images (see Figure 5).…”

Section: Close-up Thermal Images Of Ryugumentioning

confidence: 77%

“…This implies that the surface physical state of Ryugu is consistent with very porous and rough surface, where boulders have high porosity (30% to 50 %) and the rest of the surrounding surface is dominated by fragments of porous rocks several centimeters larger than the thermal skin depth [4]. It is important that the surface physical state predicted from the global thermal images was confirmed later by the close-up thermal imaging by TIR and also by the optical surface imaging and thermal radiation measurements from the surface lander Mobile Asteroid Surface Scout (MASCOT) [27,28].…”

Section: Global Thermal Images Of Ryugumentioning

confidence: 99%

Thermography of Asteroid and Future Applications in Space Missions

Okada

2020

Applied Sciences

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Featured Application: Activities in lunar, planetary, and asteroid science and exploration.Abstract: The Near-Earth Asteroid 162173 Ryugu is a C-type asteroid which preserves information about the ancient Solar System and is considered enriched in volatiles such as water and organics associated with the building blocks of life, and it is a potentially hazardous object that might impact Earth. Hayabusa2 is the asteroid explorer organized by the Japan Aerospace Exploration Agency to rendezvous with the asteroid and collect surface materials to return them to Earth. Thermography has been carried out from Hayabusa2 during the asteroid proximity phase, to unveil the thermophysical properties of the primitive Solar System small body, which offered a new insight for understanding the origin and evolution of the Solar System, and demonstrated the technology for future applications in space missions. Global, local, and close-up thermal images taken from various distances from the asteroid strongly contributed to the mission success, including suitable landing site selection, safe assessment during descents into the thermal environments and hazardous boulder abundance, and the detection of deployable devices against the sunlit asteroid surface. Potential applications of thermography in future planetary missions are introduced.

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Images from the surface of asteroid Ryugu show rocks similar to carbonaceous chondrite meteorites

Cited by 110 publications

References 38 publications

Photometry of Particles Ejected From Active Asteroid (101955) Bennu

Photometry of Particles Ejected From Active Asteroid (101955) Bennu

Magnetic Properties of Asteroid (162173) Ryugu

Thermography of Asteroid and Future Applications in Space Missions

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