162173 Ryugu#Shape

Ryugu was discovered on 10 May 1999 by astronomers with the Lincoln Near-Earth Asteroid Research at the Lincoln Lab's ETS near Socorro, New Mexico, in the United States. It was given the provisional designation {{mp|1999 JU|3}}. The asteroid was officially named "Ryugu" by the Minor Planet Center on 28 September 2015 ({{small|M.P.C. 95804}}). The name refers to Ryūgū-jō (Dragon Palace), a magical underwater palace in a Japanese folktale. In the story, the fisherman Urashima Tarō travels to the palace on the back of a turtle, and when he returns, he carries with him a mysterious box, much like Hayabusa2 returning with samples.

Ryugu formed as part of an asteroid family, belonging either to Eulalia or Polana.{{Cite journal|last1=Sugita|first1=S.|last2=Honda|first2=R.|last3=Morota|first3=T.|last4=Kameda|first4=S.|last5=Honda|first5=C.|last6=Yokota|first6=Y.|last7=Yamada|first7=M.|last8=Kouyama|first8=T.|last9=Sakatani|first9=N.|last10=Suzuki|first10=H.|last11=Yoshioka|first11=K.|date=March 2019|title=The Evolution of Ryugu's Parent Body Constrained by Hayabusa2 Imaging Observations|journal=LPI|language=en|issue=2132|pages=2622|bibcode=2019LPI....50.2622S}} Those asteroid families are most likely fragments of past asteroid collisions. The large number of boulders on the surface supports a catastrophic disruption of the parent body. The parent body of Ryugu probably experienced dehydration due to internal heating and must have formed in an environment without a strong magnetic field. After this catastrophic disruption, part of the surface was reshaped again by the high speed rotation of the asteroid forming the equatorial ridge (Ryujin Dorsum), through internal failure and/or mass wasting. The geologically distinct western area ('Western bulge') is probably the result of asymmetrical internal failure. It is hoped that surface samples will help to reveal more of the geological history of the asteroid.

Ryugu is hypothesized to be an extinct comet.{{cite journal |last1=Miura |first1=H. |last2=Nakamura |first2=E. |last3=Kunihiro |first3=T. |title=The Asteroid 162173 Ryugu: a Cometary Origin |journal= The Astrophysical Journal Letters|date=2022 |volume=925 |issue=2 |page=15|doi=10.3847/2041-8213/ac4bd5 |bibcode=2022ApJ...925L..15M |doi-access=free }}

{{stack|File:Animation of 162173 Ryugu, 495 Eulalia and 142 Polana.gif or 142 Polana.{{cite journal |title=The geomorphology, color, and thermal properties of Ryugu: Implications for parent-body processes |journal=Science |volume=364 |issue=6437 |pages=eaaw0422 |author=S. Sugita |display-authors=etal|date=19 Mar 2019 |doi=10.1126/science.aaw0422 |pmid=30890587 |pmc=7370239 |bibcode=2019Sci...364..252S |hdl=1893/29363 |hdl-access=free }}
{{legend2| Yellow| Sun}}{{·}}{{legend2| RoyalBlue| Earth}}{{·}}{{legend2|Lime| 162173 Ryugu}}{{·}}{{legend2|OrangeRed| 142 Polana}}{{·}}{{legend2|Cyan| 495 Eulalia}}]]}}

Ryugu orbits the Sun at a distance of 0.96–1.41 AU once every 16 months (474 days; semi-major axis of 1.19 AU). Its orbit has an eccentricity of 0.19 and an inclination of 6° with respect to the ecliptic. It has a minimum orbital intersection distance with Earth of {{cvt|0.000638|AU|km|3|order=flip}}, equivalent to 0.23 lunar distances.

Early analysis in 2012 by Thomas G. Müller et al. used data from a number of observatories, and suggested that the asteroid was "almost spherical", a fact that hinders precise conclusions, with retrograde rotation, an effective diameter of 0.85–0.88 km (0.528 miles) and a geometric albedo of 0.044 to 0.050. They estimated that the grain sizes of its surface materials are between 1 and 10 mm.

Initial images taken by the Hayabusa2 spacecraft on approach at a distance of {{cvt|700|km}} were released on 14 June 2018. They revealed a diamond-shaped body {{val|1|u=km}} in diameter and confirmed its Retrograde motion Between 17 and 18 June 2018, Hayabusa2 went from {{cvt|330|to|240|km}} from Ryugu and captured a series of additional images from the closer approach. Astronomer Brian May created stereoscopic images from data collected a few days later.{{cite news |last=Bartels |first=Meghan |title=Queen's Brian May Will Rock You with This Stereo Image of Asteroid Ryugu |url=https://www.space.com/41119-brian-may-asteroid-ryugu-hayabusa2-image.html |date=10 July 2018 |work=Space.com |access-date=24 December 2018 }} After a few months of exploration, JAXA scientists concluded that Ryugu is actually a rubble pile with about 50% of its volume being empty space.[https://www.bbc.com/news/science-environment-47633649 Hayabusa-2: Asteroid mission exploring a 'rubble pile'.] Paul Rincon, BBC News. 19 March 2019.

The acceleration due to gravity at the equator has been evaluated at about 0.11 mm/s², rising to 0.15 mm/s² at the poles. The mass of Ryugu is estimated at 450 million tonnes. The asteroid has a volume of 0.377 ± 0.005 km³ and a bulk density of 1.19 ± 0.03 g/cm³ based on the shape model.{{Cite journal|last1=Watanabe|first1=S.|last2=Hirabayashi|first2=M.|last3=Hirata|first3=N.|last4=Hirata|first4=N.|last5=Noguchi|first5=R.|last6=Shimaki|first6=Y.|display-authors=etal|date=April 2019|title=Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu—A spinning top–shaped rubble pile|journal=Science|volume=364 |language=en|issue=6437|pages=268–272|doi=10.1126/science.aav8032|bibcode=2019Sci...364..268W|pmid=30890588|s2cid=84183033 |doi-access=free}}

File:Ryugu rotation.gif

Ryugu has a round shape with an equatorial ridge, called Ryujin Dorsum. Ryugu is a spinning top-shape asteroid similar to Bennu. The ridge was shaped by strong centrifugal forces during a phase of high-speed rotation, through landslides and/or internal failure. The western side, also called the western bulge, has a distinct shape. It has a smooth surface with a sharp equatorial ridge. When modeling a high-speed rotation of present-day Ryugu, subsurface material appears structurally intact and relaxed in the western bulge, while other regions are more sensitive to structural failure. This indicates past structural failure in the western bulge (only the elements that did not experience structural failure previously are now sensitive to failure).{{Cite journal |last1=Hirabayashi |first1=Masatoshi |last2=Tatsumi |first2=Eri|last3=Miyamoto |first3=Hideaki |last4=Komatsu |first4=Goro |last5=Sugita |first5=Seiji |last6=Watanabe |first6=Sei-ichiro |last7=Scheeres |first7=Daniel J. |last8=Barnouin |first8=Olivier S. |last9=Michel |first9=Patrick |last10=Honda |first10=Chikatoshi |last11=Michikami |first11=Tatsuhiro |date=March 2019 |title=The Western Bulge of 162173 Ryugu Formed as a Result of a Rotationally Driven Deformation Process |journal=Astrophysical Journal Letters |language=en |volume=874 |issue=1 |pages=L10 |doi=10.3847/2041-8213/ab0e8b |arxiv=1904.03480 |bibcode=2019ApJ...874L..10H |s2cid=102350610 |issn=0004-637X |doi-access=free }} The western bulge is bordered by the Tokoyo and Horai Fossae.

File:Images of asteroid Ryugu from the wide angle Optical Navigation Cameras (ONC-W1 and ONC-W2) via Hayabusa2.jpg]]

Observations from Hayabusa2 showed that the surface of Ryugu is very young and has an age of {{nowrap|8.9 ± 2.5 million}} years based on the data collected from the artificial crater that was created with an explosive by Hayabusa2.{{Cite journal|last1=Arakawa|first1=M.|last2=Saiki|first2=T.|last3=Wada|first3=K.|last4=Ogawa|first4=K.|last5=Kadono|first5=T.|last6=Shirai|first6=K.|last7=Sawada|first7=H.|last8=Ishibashi|first8=K.|last9=Honda|first9=R.|last10=Sakatani|first10=N.|last11=Iijima|first11=Y.|date=2020-03-19|title=An artificial impact on the asteroid 162173 Ryugu formed a crater in the gravity-dominated regime|url=https://www.science.org/doi/10.1126/science.aaz1701|journal=Science|volume=368|issue=6486|pages=67–71|language=en|doi=10.1126/science.aaz1701|pmid=32193363|bibcode=2020Sci...368...67A|s2cid=214591738|issn=0036-8075}}

The surface of Ryugu is porous and contains no or very little dust. The measurements with the radiometer on board of MASCOT, which is called MARA, showed a low thermal conductivity of the boulders. This was an in situ measurement of the high porosity of the boulder material. This result showed that most meteorites originating from C-type asteroids are too fragile to survive the entry into Earth's atmosphere.{{Cite web|url=https://www.dlr.de/content/en/articles/news/2019/03/20190715_mascot-confirms-what-scientists-have-long-suspected.html|title=DLR – MASCOT confirms what scientists have long suspected|website=DLRARTICLE DLR Portal|language=en|access-date=2020-03-07}}{{Cite journal|last1=Grott|first1=M.|last2=Knollenberg|first2=J.|last3=Hamm|first3=M.|last4=Ogawa|first4=K.|last5=Jaumann|first5=R.|last6=Otto|first6=K. A.|last7=Delbo|first7=M.|last8=Michel|first8=P.|last9=Biele|first9=J.|last10=Neumann|first10=W.|last11=Knapmeyer|first11=M.|date=2019-07-15|title=Low thermal conductivity boulder with high porosity identified on C-type asteroid (162173) Ryugu|journal=Nature Astronomy|language=en|volume=3|issue=11|pages=971–976|doi=10.1038/s41550-019-0832-x|bibcode=2019NatAs...3..971G|hdl=1893/29871|s2cid=197402876|issn=2397-3366|hdl-access=free}} The images from the camera of MASCOT, which is called MASCam, showed that surface of Ryugu contains two different almost black types of rock with little internal cohesion, but no dust was detected. One type of rocky material on the surface is brighter with a smooth surface and sharp edges. The other type of rock is dark with a cauliflower-like, crumbly surface. The dark type of rock has a dark matrix with small, bright, spectrally different inclusions. The inclusions appear similar to CI chondrites.{{Cite journal|last1=Jaumann|first1=R.|last2=Schmitz|first2=N.|last3=Ho|first3=T.-M.|last4=Schröder|first4=S. E.|last5=Otto|first5=K. A.|last6=Stephan|first6=K.|last7=Elgner|first7=S.|last8=Krohn|first8=K.|last9=Preusker|first9=F.|last10=Scholten|first10=F.|last11=Biele|first11=J.|date=2019-08-23|title=Images from the surface of asteroid Ryugu show rocks similar to carbonaceous chondrite meteorites|journal=Science|language=en|volume=365|issue=6455|pages=817–820|doi=10.1126/science.aaw8627|issn=0036-8075|pmid=31439797|bibcode=2019Sci...365..817J|s2cid=201616571|url=https://hal.archives-ouvertes.fr/hal-02381801/file/aaw8627_CombinedPDF_v3.pdf }}{{Cite web|url=https://www.dlr.de/content/en/articles/news/2019/03/20190822_the-near-earth-asteroid-ryugu-a-fragile-cosmic-rubble-pile.html|title=The near-Earth asteroid Ryugu – a fragile cosmic rubble pile|website=DLRARTICLE DLR Portal|language=en|access-date=2020-03-07}} An unanticipated side effect from the Hayabusa2 thrusters revealed a coating of dark, fine-grained red material.{{Cite web|title=Hayabusa-2 Reveals Surface of Near-Earth Asteroid Ryugu in Stunning Detail|url=http://www.sci-news.com/space/hayabusa-2-surface-near-earth-asteroid-ryugu-08415.html|date=May 11, 2020|website=Sci News|access-date=May 12, 2020}}

Ryugu has 77 craters on the surface. Ryugu shows variations of crater density that cannot be explained by randomness of cratering. There are more craters at lower latitudes and fewer at higher latitudes, and fewer craters in the western bulge (160°E – 290°E) than in the region around the meridian (300°E – 30°E). This variation is seen as evidence of a complicated geologic history of Ryugu.{{Cite journal|last1=Hirata|first1=Naoyuki|last2=Morota|first2=Tomokatsu|last3=Cho|first3=Yuichiro|last4=Kanamaru|first4=Masanori|last5=Watanabe|first5=Sei-ichiro|last6=Sugita|first6=Seiji|last7=Hirata|first7=Naru|last8=Yamamoto|first8=Yukio|last9=Noguchi|first9=Rina|last10=Shimaki|first10=Yuri|last11=Tatsumi|first11=Eri|date=March 2020|title=The spatial distribution of impact craters on Ryugu|journal=Icar|language=en|volume=338|pages=113527|doi=10.1016/j.icarus.2019.113527|arxiv=2205.05818 |bibcode=2020Icar..33813527H|s2cid=209903294|issn=0019-1035}} The surface has one artificial crater, which was intentionally formed by the Small Carry-on Impactor (SCI), which was deployed by Hayabusa2. SCI fired a 2 kg copper mass onto the surface of Ryugu on 5 April 2019.{{Cite web|url=http://www.hayabusa2.jaxa.jp/en/topics/20190424e_CRA2_Schedule/|title=Apr. 24, 2019. What's new|website=JAXA Hayabusa2 project|language=ja|access-date=2020-03-09}} The artificial crater showed a darker subsurface material. It created an Ejecta of 1 cm thickness and excavated material from up to 1 metre in depth.{{Cite web|url=http://www.hayabusa2.jaxa.jp/en/enjoy/material/press/Hayabusa2_Press20190625_ver5_en2.pdf|title=Asteroid explorer, Hayabusa2, reporter briefing|date=June 25, 2019|website=JAXA Hayabusa2 Project|access-date=2020-03-09}}

Ryugu contains 4,400 boulders with a size larger than 5 metres. Ryugu has more large boulders per surface area than Itokawa or Bennu, about one boulder larger than 20 metres per 50 km². The boulders resemble laboratory impact fragments. The high number of boulders is explained with a catastrophic disruption of Ryugu's larger parent body. The largest boulder, called Otohime, has a size of ~160 × 120 × 70 m and is too large to be explained as an ejected boulder from a crater.{{Cite journal|last1=Michikami|first1=Tatsuhiro|last2=Honda|first2=Chikatoshi|last3=Miyamoto|first3=Hideaki|last4=Hirabayashi|first4=Masatoshi|last5=Hagermann|first5=Axel|last6=Irie|first6=Terunori|last7=Nomura|first7=Keita|last8=Ernst|first8=Carolyn M.|last9=Kawamura|first9=Masaki|last10=Sugimoto|first10=Kiichi|last11=Tatsumi|first11=Eri|date=October 2019|title=Boulder size and shape distributions on asteroid Ryugu|journal=Icar|language=en|volume=331|pages=179–191|doi=10.1016/j.icarus.2019.05.019|bibcode=2019Icar..331..179M|issn=0019-1035|doi-access=free|hdl=1893/29777|hdl-access=free}}

After the initial description (phase-1), part of the sample was distributed to the Hayabusa2 Initial Analysis Team, consisting of six sub-teams, and two Phase-2 curation institutes at Okayama University and JAMSTEC Kochi Institute for Core Sample Research.{{Cite web |title=JAXA {{!}} Asteroid Explorer Hayabusa2 Initial Analysis Chemical Analysis Team reveals aqueous alteration and primitive composition of asteroid Ryugu |url=https://global.jaxa.jp/press/2022/06/20220610-2_e.html |access-date=2022-09-28 |website=JAXA {{!}} Japan Aerospace Exploration Agency |language=en}}

In September 2022 the Hayabusa 2 initial Analysis Stone Team announced the results of their study, which includes:{{Cite web |title=JAXA {{!}} Asteroid Explorer Hayabusa2 Initial Analysis Stone Team reveals the formation and evolution of carbonaceous asteroid Ryugu. |url=https://global.jaxa.jp/press/2022/09/20220923-1_e.html |access-date=2022-09-28 |website=JAXA {{!}} Japan Aerospace Exploration Agency |language=en}}

• Ryugu samples contain grains that were formed at high temperatures above 1000 °C, which formed close to the Sun and were later transported towards the outer Solar System.
• The samples are soft enough to be cut with a knife and the samples preserve the magnetic field like a hard disk.
• A simulation of the formation was performed, which showed that the parent body of Ryugu accumulated 2 million years after the formation of the Solar System. It heated up to 50 °C over the next 3 million years, resulting in reactions of rocky material with water. In these reactions anhydrous silicates became hydrous silicates and iron became magnetite. The 100 km large parent body was then destroyed by a <10 km large impactor, with an impact speed of about 5 km/s. Ryugu then formed from material far from the impact.

The deuterium-rich and nitrogen-15-rich isotopic compositions of fine-grained minerals and organics suggests that the parent body of Ryugu formed in the outer Solar System.{{Cite web |title=JAXA {{!}} Asteroid Ryugu is a drifter from the outer Solar System: Results from the Hayabusa2 Phase-2 Curation Kochi Team published in Nature Astronomy |url=https://global.jaxa.jp/press/2022/08/20220816-1_e.html |access-date=2022-09-28 |website=JAXA {{!}} Japan Aerospace Exploration Agency |language=en}} Titanium, chromium and molybdenum isotopic anomalies provide more evidence that ties Ryugu's origin to the outer Solar System.{{Cite journal |date=2022 |title=Ryugu's nucleosynthetic heritage from the outskirts of the Solar System Science Advances (2022): eadd8141. |journal=Science Advances |volume=8 |issue=46 |pages=3 |doi=10.1126/sciadv.add8141 |last1=Hopp |first1=Timo |last2=Dauphas |first2=Nicolas |last3=Abe |first3=Yoshinari |last4=Aléon |first4=Jérôme |last5=O'd. Alexander |first5=Conel M. |last6=Amari |first6=Sachiko |last7=Amelin |first7=Yuri |last8=Bajo |first8=Ken-Ichi |last9=Bizzarro |first9=Martin |last10=Bouvier |first10=Audrey |last11=Carlson |first11=Richard W. |last12=Chaussidon |first12=Marc |last13=Choi |first13=Byeon-Gak |last14=Davis |first14=Andrew M. |last15=Di Rocco |first15=Tommaso |last16=Fujiya |first16=Wataru |last17=Fukai |first17=Ryota |last18=Gautam |first18=Ikshu |last19=Haba |first19=Makiko K. |last20=Hibiya |first20=Yuki |last21=Hidaka |first21=Hiroshi |last22=Homma |first22=Hisashi |last23=Hoppe |first23=Peter |last24=Huss |first24=Gary R. |last25=Ichida |first25=Kiyohiro |last26=Iizuka |first26=Tsuyoshi |last27=Ireland |first27=Trevor R. |last28=Ishikawa |first28=Akira |last29=Ito |first29=Motoo |last30=Itoh |first30=Shoichi |pmid=36264823 |s2cid=253045585 |display-authors=1 |doi-access=free |hdl=20.500.11850/583897 |hdl-access=free }}

Based on preserved magnetism in the samples researchers concluded that the parent body of Ryugu was probably formed in the darkness of nebular gas.

The Hayabusa2 sample capsule was significantly upgraded from Hayabusa, to preserve water, light organics, gases, and other volatiles.{{cite journal |last1=Yada |first1=T. |last2=Fujimura |last3=Abe M. |last4=Nakamura T. |last5=Noguchi T |last6=Okazaki R. |last7=Nagao K. |last8=Ishibashi Y. |last9=Shirai K. |last10=Zolensky M. E. |last11=Sandford S. |last12=Okada |first12=T. |last13=Uesugi M. |last14=Karouji Y. |last15=Ogawa M. |last16=Yakame S. |last17=Ueno M. |last18=Mukai T. |last19=Yoshikawa M. |last20=Kawaguchi J.|date= 2014 |title=Hayabusa-returned sample curation in the Planetary Material Sample Curation Facility of JAXA |journal=Met. & Planet. Sci. |volume=49 |issue=2 |page=135 |doi=10.1111/maps.12027 |bibcode=2014M&PS...49..135Y |s2cid=56357760 |doi-access=free }}{{cite conference |last1=Abe |first1=M. |last2=Yada |first2=T. |last3=Okada |first3=T. |last4=Sakamoto |first4=K. |last5=Yoshitake |first5=M. |last6=Nakano Y. |last7=Matsumoto |first7=T. |last8=Kawasaki |first8=N. |last9=Kumagai |first9=K. |last10=Matsui S. |last11=Nishimura |first11=M. |last12=Yurimoto |first12=H. |date=2017 |title=Readiness of Receiving and Curation facility for Hayabusa2 Asteroid Sample Return Mission |conference=Hayabusa 2017 |url=https://curation.isas.jaxa.jp/symposium/abstract/2017/1204_1100_Masanao_Abe.pdf}} This water was successfully sampled and preserved.{{cite conference |last=Nittler |first=L. R. |date=2022 |title=Can SIMS measurements constrain the D/H ratio of water on Ryugu? |conference=2022 Hayabusa Symposium |page=S21-02 }}{{cite conference |last1=Piani |first1=L. |last2=Marrocchi |last3=Nagashima |last4=Kawasaki |first4= |last5=Sakamoto |first5=|last6=Bajo |first6=|last7=Yurimoto |first7= |date=2022 |title=H isotopic composition of water in Ryugu samples returned by the Hayabusa2 mission |conference=85th MetSoc |page=6058 }}{{cite conference |last1=Nittler |first1=L. R. |last2=Barosch |first2=J. |last3=Wang |first3=J. |last4=Alexander |first4=C. M. O'D. |date=2023 |title=Water in Asteroid Ryugu is Deuterium-Rich Compared to Earth and CI Chondrites |conference=54th LPSC |page= }}{{cite conference |last1=Yesiltas |first1=M. |last2=Glotch |first2=T. D. |last3= Kebukawa |first3=Y. |last4=Northrup |first4=P. |last5=Sava |first5=B. |date=2023 |title=Nano-Scale Infrared and Raman Spectroscopy of Ryugu Particles |conference=86th Meteoritical Society Meeting |page=6161 }} Via a bulk sample (~95 milligrams), its water content was reported as 6.84 ±0.34 wt%.{{cite journal |last1=Yokoyama |first1=T. |last2=Nagashima K. |last3=Nakai I. |last4=Young E. D. |author5=((and 145 coauthors)) |title=Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites |journal=Science |date=2023 |volume=379 |issue=6634|doi=10.1126/science.abn7850 |pmid=35679354 |bibcode=2023Sci...379.7850Y |s2cid=249544031 |url=https://hal.science/hal-03825124/file/Yokoyama-et-al_2022_science.abn7850.pdf }}

Independently, a research group with a far smaller allocation (particles) reported 4-7 percent water.{{cite conference |last1=Verchovsky |first1=A. B. |last2=Abernethy |first2=F. A. J. |last3=Anand |first3=M. |last4=Franchi |first4=I. A. |last5=Grady |first5=M. M. |last6=Greenwood |first6=R. C. |last7=Suttle |first7=M. |last8=Ito |first8=M. |last9=Tomioka |first9=N. |last10=Uesugi |first10=M. |last11=Yamaguchi |first11=A. |last12=Kimura |first12=M. |last13=Imae |first13=N. |last14=Shirai |first14=N. |last15=Ohigashi |first15=T. |last16=Liu |first16=M-C. |last17=Yada |first17=T. |last18=Abe |first18=M. |last19=Usui |first19=T. |date=2023 |title=Ryugu's volatiles investigated using stepped combustion and EGA methods |conference=54th LPSC |page=2471 }}

The lower-than-expected water signature seen by Hayabusa2 instruments was the result of space weathering, producing a dehydrated rind.{{cite journal |last1=Taaki |last2=Noguchi T. |last3=Matsumoto |first3=Y |last4=Tsuda |date=19 Dec 2022 |title=A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu |journal=Nature |volume=7 |page=170 |doi=10.1038/s41550-022-01841-6 |bibcode=2023NatAs...7..170N |s2cid=254908999 |doi-access=free |pmid=36845884 |hdl=2433/279328 |hdl-access=free }}{{cite conference |last1=Tachibana |first1=S. |title=Hayabusa2 and Sample Science – JAXA |conference=NASA Small Bodies Assessment Group July 2023 Meeting |date=Jul 12, 2023}}{{cite conference |last1=Hamann |first1=C. |last2=Bonato E. |last3=Maturilli A. |last4=Mahlow K. |last5=Patzschke M. |last6=Alemanno G. |last7=Schwinger S. |last8=Van den Neucker A. |last9=Baqué M. |last10=Greshake A. |last11=Hecht L. |last12=Helbert J. |title=CRISPY On The OUTSIDE, RAW On The INSIDE: IMPACT-INDUCED MELTING And FRAGMENTATION Of C-Type ASTEROID Regolith DocumentedIn A Ryugu Sample |conference=86th Meteoritical Society Meeting |date=Aug 11, 2023 |page=6296}}

Carbonated liquid water was discovered in one crystal. The water contained salts and organic matter. The liquid water was found inside a hexagonal iron sulfide crystal. The carbon dioxide was most likely CO₂-ice (dry ice) inside the parent body. The water ice melted soon after the parent body formed and the CO₂ dissolved into the water.{{cite conference |last1=Zolensky |first1=M. |last2=Dolocan |first2=A. |last3=Bodnar |first3=R. |last4=Gearba |first4=I. |last5=Martinez |first5=J. |last6=Han |first6=J. |last7=Nakamura |first7=T. |last8=Tsuchiyama |first8=A. |last9=Matsuno |first9=J. |last10=Sun |first10=M. |last11=Matsumoto |first11=M. |last12=Fujioka |first12=Y. |last13=Enokido |first13=Y. |last14=Uesugi |first14=K. |last15=Takeuchi |first15=A. |last16=Yasutake |first16=M. |last17=Miyake |first17=A. |last18=Okumura |first18=S. |last19=Mitsukawa |first19=I. |last20=Takigawa |first20=A. |last21=Mikouchi |first21=T. |last22=Enju |first22=S. |last23=Morita |first23=T. |last24=Kikuiri |first24=M. |last25=Amano |first25=K. |last26=Yurimoto |first26=H. |last27=Noguchi |first27=T. |last28=Okazaki |first28=R. |last29=Yabuta |first29=H. |last30=Naraoka |first30=H. |last31=Sakamoto |first31=K. |last32=Tachibana |first32=S. |last33=Watanabe |first33=S. |last34=Tsuda |first34=Y |date=2022 |title=Direct Measurement of the Composition of Aqueous Fluids from the Parent Body of Asteroid 162173 Ryugu |conference=53rd Lun. Plan. Sci. Conf |page=1451 }}{{cite conference |last1=Nakamura |first1=T |last2=Matsumoto |first2=M. |last3=Amano |first3=K. |author4=((and 70+ coauthors)) |date=2022 |title=Early History of Ryugu's Parent Asteroid: Evidence from Return Sample |conference=53rd LPSC |page=1753 }}

Crystals "shaped like coral reefs" were found. These crystals probably formed in liquid water, which was once present in the interior of the parent body. The parent body had a dryer surface and a wetter interior. After the collision of the parent body with a smaller asteroid, the interior and surface material were mixed. Today Ryugu has both interior and parent body surface material on its surface.

An international team found particles in the samples that contained small amounts of material unaltered by water. The team found about 0.5 vol% of anhydrous silicates. The isotopic analysis of the magnesium-rich olivine and pyroxene in the sample suggests that two types of high-temperature objects accreted onto the surface of Ryugu: amoeboid olivine aggregates and magnesium-rich chondrules.{{Cite web |title=Team identifies parent body materials in Ryugu asteroid |url=https://www.llnl.gov/news/team-identifies-parent-body-materials-ryugu-asteroid |access-date=2022-09-28 |website=www.llnl.gov |language=en}}

Hayabusa2 recovered helium and other noble gases. Some terrestrial contamination entered the system, but the Ryugu components are still measurable.{{cite journal |last1=Okazaki |first1=R. |last2=Miura |first2=Y. N. |last3=Takano |first3=Y. |last4=Sawada |first4=H. |last5=Sakamoto |first5=K. |last6=Yada |first6=T. |last7=Yamada |first7=K. |last8=Kawagucci |first8=S. |last9=Matsui |first9=Y. |author10= ((and 115 others)) |date=20 Oct 2022 |title=First asteroid gas sample delivered by the Hayabusa2 mission: a treasure box from Ryugu |journal=Science Advances |volume=8 |issue=46 |pages=eabo7239 |doi=10.1126/sciadv.abo7239 |pmid=36264781 |bibcode=2022SciA....8O7239O |s2cid=253045236 |doi-access=free |hdl=20.500.11850/583894 |hdl-access=free }}{{cite journal |last1=Okazaki |first1=R. |last2=Marty |first2=B. |last3=Busemann |first3=H. |last4=Hashizumi |first4=K. |last5=Gilmour |first5=J. D. |last6=Meshik |first6=A. |last7=Yada |first7=T. |last8=Kitajima |first8=F. |last9=Broadley |first9=M. W. |author10=((and 114 others)) |date=2023 |title=Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution |journal=Science |volume=379 |issue=6634 |doi=10.1126/science.abo0431 |bibcode=2023Sci...379.0431O |s2cid=253045328 |url=https://hal.science/hal-03891762 }}{{cite conference |last1=Busemann |first1=H. |last2=Krietsch D. |last3=Mertens C. A. K. |last4=Maden C. |title=Recently Recovered Pristine Extraterrestrial Materials As Carriers of Primordially Trapped Noble Gases |conference=86th Meteoritical Society Meeting |date=Aug 11, 2023 |page=6211 }}{{cite conference |last1=Verchovsky |first1=A. B. |last2=Abernethy |first2=F. A. J. |last3=Anand |first3=M. |last4=Franchi |first4=I. A. |last5=Grady |first5=M. M. |last6=Greenwood |first6=R. C. |last7=Barber |first7=S. J. |last8=Suttle |first8=M. |last9=Ito |first9=M. |last10=Tomioka |first10=N. |last11=Uesugi |first11=M. |last12=Yamaguchi |first12=A. |last13=Kimura |first13=M. |last14=Imae |first14=N. |last15=Shirai |first15=N. |last16=Ohigashi |first16=T. |last17=Liu |first17=M-C. |last18=Yada |first18=T. |last19=Abe |first19=M. |last20=Usui |first20=T. |date=2023 |title=Extremely High Xe Concentration in The Hayabusa2 C0209 Sample |conference=54th LPSC |page=6323 }}

Aliphatic carbon-rich organics associated with coarse-grained phyllosilicates were found. Such an association has not been observed in any meteorite study and could be unique to the asteroid Ryugu.

In samples retrieved on Ryugu from the Japanese Hayabusa2 spacecraft, scientists discovered 20 different amino acids.[https://www.livescience.com/20-amino-acid-types-found-on-ryugu 'Rubber-ducky' asteroid 200 million miles away holds building blocks of life] Ben Turner, LiveScience. June 9th, 2022

In March 2023, scientists announced that uracil and vitamin B3 were detected in samples retrieved from Ryugu. Unlike previous instances when nucleobases and vitamins were found in certain carbon-rich meteorites, the samples were collected directly from the asteroid and delivered to Earth in sealed capsules, which meant Earthside contamination was not possible.{{cite web | url =https://edition.cnn.com/2023/03/21/world/ryugu-asteroid-organic-molecules-scn/index.html|title=RNA compound and vitamin B3 found in samples from near-Earth asteroid|publisher=CNN| author=Ashley Strickland|date=22 March 2023| accessdate =22 March 2023}}{{Cite journal |last1=Oba |first1=Yasuhiro |last2=Koga |first2=Toshiki |last3=Takano |first3=Yoshinori |last4=Ogawa |first4=Nanako O. |last5=Ohkouchi |first5=Naohiko |last6=Sasaki |first6=Kazunori |last7=Sato |first7=Hajime |last8=Glavin |first8=Daniel P. |last9=Dworkin |first9=Jason P. |last10=Naraoka |first10=Hiroshi |last11=Tachibana |first11=Shogo |last12=Yurimoto |first12=Hisayoshi |last13=Nakamura |first13=Tomoki |last14=Noguchi |first14=Takaaki |last15=Okazaki |first15=Ryuji |date=2023-03-21 |title=Uracil in the carbonaceous asteroid (162173) Ryugu |journal=Nature Communications |language=en |volume=14 |issue=1 |pages=1292 |doi=10.1038/s41467-023-36904-3 |pmid=36944653 |bibcode=2023NatCo..14.1292O |s2cid=257641373 |issn=2041-1723|doi-access=free |pmc=10030641 }}

NanoSIMS-based analysis at the Carnegie Institution found that the Ryugu samples contained grains older than the solar system. The abundance and composition of these presolar grains were similar when compared to presolar grains in CI chondrites.{{Cite journal |last1=Barosch |first1=Jens |last2=Nittler |first2=Larry R. |last3=Wang |first3=Jianhua |last4=Alexander |first4=Conel M. O'D. |last5=De Gregorio |first5=Bradley T. |last6=Engrand |first6=Cécile |last7=Kebukawa |first7=Yoko |last8=Nagashima |first8=Kazuhide |last9=Stroud |first9=Rhonda M. |last10=Yabuta |first10=Hikaru |last11=Abe |first11=Yoshinari |last12=Aléon |first12=Jérôme |last13=Amari |first13=Sachiko |last14=Amelin |first14=Yuri |last15=Bajo |first15=Ken-ichi |date=2022-08-01 |title=Presolar Stardust in Asteroid Ryugu |journal=The Astrophysical Journal |volume=935 |issue=1 |pages=L3 |doi=10.3847/2041-8213/ac83bd |arxiv=2208.07976 |bibcode=2022ApJ...935L...3B |s2cid=251538946 |issn=0004-637X |doi-access=free }} Researchers using the particle accelerator in J-PARC, used Muon beams to analyse the chemical composition of the samples. The researchers found a similar composition when compared to CI chondrites, but a 25% lower oxygen abundance relative to silicon for the Ryugu samples. The oxygen excess in meteorites might come from contamination after they entered earth's atmosphere.{{Cite web |date=2022-09-23 |title=Researchers have used beams of muons to analyze the elemental composition of Asteroid Ryugu samples |url=https://www.ipmu.jp/en/20220923-Ryugu |access-date=2022-09-28 |website=Kavli IPMU-カブリ数物連携宇宙研究機構 |language=en}}

No magnetic field was detected near Ryugu on a global or local scale. This measurement is based on the magnetometer on board of MASCOT, which is called MasMag. This shows that Ryugu does not generate a magnetic field, indicating that the larger body from which it was fragmented was not generated in an environment with a strong magnetic field. This result cannot be generalized for C-type asteroids, however, because the surface of Ryugu seems to have been recreated in a catastrophic disruption.{{Cite journal|last1=Hercik|first1=David|last2=Auster|first2=Hans-Ulrich|last3=Constantinescu|first3=Dragos|last4=Blum|first4=Jürgen|last5=Fornaçon|first5=Karl-Heinz|last6=Fujimoto|first6=Masaki|last7=Gebauer|first7=Kathrin|last8=Grundmann|first8=Jan-Thimo|last9=Güttler|first9=Carsten|last10=Hillenmaier|first10=Olaf|last11=Ho|first11=Tra-Mi|date=2020|title=Magnetic Properties of Asteroid (162173) Ryugu|journal=Journal of Geophysical Research: Planets|language=en|volume=125|issue=1|pages=e2019JE006035|doi=10.1029/2019JE006035|bibcode=2020JGRE..12506035H|issn=2169-9100|doi-access=free|hdl=1721.1/136097.2|hdl-access=free}}

As of August 2019, there are 13 surface features that are named by the IAU.Jason Davis [http://www.planetary.org/blogs/jason-davis/hayabusa2-updates-sample-collection.html Hayabusa2 team sets date for sample collection, considers two touchdown sites] Planetary.org January 16, 2019{{Cite web|url=http://www.hayabusa2.jaxa.jp/en/topics/20190121e_Nomenclature/|title = Jan. 21, 2019. What's new}} The three landing sites are not officially confirmed but are referred to by specific names in media by JAXA. The theme of features on Ryugu is "children's stories". Ryugu was the first object to introduce the feature type known as the saxa, referring to the large boulders found on Ryugu's surface.

A dorsum is a ridge. There is a single dorsum on Ryugu.

A fossa is a ditch-like feature.

A saxum is a large boulder. Ryugu is the first astronomical object with them being named. Two boulders have been named "Styx" and "Small Styx" unofficially by the JAXA team; it is unknown if these names will be submitted for IAU approval. Both names refer to the River Styx.{{cite web |title=July 8, 2019. What's new |url=http://www.hayabusa2.jaxa.jp/en/topics/20190708e_PPTD_approach2/ |website=JAXA Hayabusa2 project |access-date=7 September 2019 |language=ja}}

{{unreferenced section|date=June 2022}}

JAXA has given informal names to the specific landing and collection sites.

{{Main|Hayabusa2}}

File:.Animation of Hayabusa2 orbit.gif}} {{legend2|lime|162173 Ryugu}} {{legend2|royalblue|Earth}} {{legend2|yellow|Sun}}]]

The Japan Aerospace Exploration Agency (JAXA) spacecraft Hayabusa2 was launched in December 2014 and successfully arrived at the asteroid on 27 June 2018. It returned material from the asteroid to Earth in December 2020.

The Hayabusa2 mission includes four rovers with various scientific instruments. The rovers are named HIBOU (aka Rover-1A), OWL (aka Rover-1B), MASCOT and Rover-2 (aka MINERVA-II-2). On 21 September 2018, the first two of these rovers, HIBOU and OWL (together the MINERVA-II-1 rovers) which hop around the surface of the asteroid, were released from Hayabusa2. This marks the first time a mission has completed a successful landing on a fast-moving asteroid body.

On 3 October 2018, the German-French Mobile Asteroid Surface Scout (MASCOT) lander successfully arrived on Ryugu, ten days after the MINERVA rovers landed. Its mission was short-lived, as was planned; the lander had only 16 hours of battery power and no way to recharge.

Hayabusa2 touched down briefly on February 22, 2019, on Ryugu, fired a small tantalum projectile into the surface to collect the cloud of surface debris within the sampling horn, and then moved back to its holding position.[https://phys.org/news/2019-02-touchdown-japan-probe-hayabusa2-distant.html Touchdown: Japan probe Hayabusa2 lands on distant asteroid.] Kyoko Hasegawa, PhysOrg. February 22, 2019. The second sampling was from the subsurface, and it involved firing a large copper projectile from an altitude of 500 metres to expose pristine material. After several weeks, it touched down on 11 July 2019 to sample the subsurface material, using its sampler horn and tantalum bullet.{{cite news |url=https://english.kyodonews.net/news/2019/07/c0805c17b10c-urgent-data-suggests-japans-hayabusa2-has-touched-down-on-asteroid.html |title=Hayabusa2 successfully collects 1st-ever subsurface samples: JAXA |agency=Kyodo News |date=11 July 2019 |access-date=15 July 2019 }}

File:41550 2021 1550 Fig5 ESM.jpg

The last rover, Rover-2 or MINERVA-II-2, failed before release from the Hayabusa2 orbiter. It was deployed anyway on 2 October 2019 in orbit around Ryugu to perform gravitational measurements. It impacted the asteroid a few days after release.

On 13 November 2019, commands were sent to Hayabusa2 to leave Ryugu and begin its journey back to Earth. On 6 December 2020 (Australian time), a capsule containing the samples landed in Australia and after a brief search was retrieved.{{cite news |last=Chang |first=Kenneth |title=Japan's Journey to an Asteroid Ends With a Hunt in Australia's Outback – The Hayabusa2 mission cements Japan's role in exploring the solar system, but finding its asteroid cargo presents one last challenge. |url=https://www.nytimes.com/2020/12/05/science/japan-asteroid-hayabusa2-woomera.html |date=5 December 2020 |work=The New York Times |access-date=5 December 2020 }}{{cite news |last=Rincon |first=Paul |title=Hayabusa-2: Capsule with asteroid samples in 'perfect' shape |url=https://www.bbc.com/news/science-environment-55201662 |date=6 December 2020 |publisher=BBC News |access-date=6 December 2020}}

Prior to the sample capsule return, the amount of sample was expected to be at least 0.1 g.{{cite web |url=https://curation.isas.jaxa.jp/curation/hayabusa2/index.html |title=Hayabusa2 Project |publisher=Astromaterials Science Research Group, Extraterrestrial Sample Curation Center, JAXA |access-date=10 December 2020 |archive-url=https://web.archive.org/web/20180925215958/https://curation.isas.jaxa.jp/curation/hayabusa2/index.html |archive-date=25 September 2018}} The description of overall bulk sample was planned to be done by JAXA in the first six months.{{cite journal |author1=安部 正真 |author2=橘 省吾 |author3=小林 桂 |author4=伊藤 元雄 |author5=渡邊 誠一郎 |script-title=ja:火の鳥「はやぶさ」未来編 その20 ～小惑星リュウグウからの リターンサンプル分析の全体像～ |language=ja |journal=日本惑星科学会誌遊星人 |volume=29 |issue=1 |pages=28–37 |year=2020 |doi=10.14909/yuseijin.29.1_28}}{{cite web |url=https://fanfun.jaxa.jp/countdown/hayabusa2/press/files/20201208_hayabusa2_1208-2.pdf |language=ja |script-title=ja:はやぶさ2試料の初期記載・分析 |author=JAXA Astromaterials Science Research Group |publisher=JAXA |access-date=10 December 2020}}{{cite web |url=http://www.hayabusa2.jaxa.jp/enjoy/material/press/Hayabusa2_Press_20201116_ver11_en2.pdf |title=Asteroid explorer, Hayabusa2, reporter briefing |date=16 November 2020 |author=((JAXA Hayabusa2 Project)) |publisher=JAXA |access-date=10 December 2020}} 5 wt% of the sample will be allocated for the detailed analysis by JAXA. 15 wt% will be allocated for initial analysis, and 10 wt% for "phase 2" analysis among Japanese research groups. Within a year, NASA (10 wt%) and international "phase 2" research groups (5 wt%) will receive their allotment. 15 wt% will be allocated for research proposals by international Announcement of Opportunity. 40 wt% of the sample will be stored unused for future analysis.

After the sample capsule returned, the amount of retrieved sample turned out to be about 5.4 g. Since it was 50 times more than anticipated, the allotment plan was adjusted to: 2 wt% to the detailed analysis by JAXA; 6 wt% for the initial analysis; 4 wt% for the "phase 2" analysis by Japanese research groups; 10 wt% for NASA; 2 wt% for the international "phase 2" research groups; 1 wt% for the public outreach; 15 wt% for the international Announcement of Opportunity; and the remaining 60 wt% will be preserved for future analysis.{{cite web |url=https://news.mynavi.jp/article/20210619-1907151/ |language=Japanese |script-title=ja:はやぶさ2の帰還サンプル、JAXA外部機関8チームでの分析が開始へ |date=19 June 2021 |publisher=TECH+ |first=Minoru |last=Ōtsuka |access-date=20 June 2021}}{{cite web |url=https://www.hayabusa2.jaxa.jp/enjoy/material/press/Hayabusa2_Press_20210617_ver6.pdf |language=Japanese |script-title=ja:小惑星探査機「はやぶさ２」記者説明会 |publisher=JAXA |date=17 June 2021 |access-date=20 June 2021}}

162173 Ryugu is the setting of Daniel Suarez's novel Delta-V, describing the adventures of eight space miners who explore near-Earth asteroid Ryugu.

• List of minor planets and comets visited by spacecraft

{{reflist|refs=

{{cite web

|type = 2016-08-09 last obs.

|title = JPL Small-Body Database Browser: 162173 Ryugu (1999 JU3)

|url = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2162173

|publisher = Jet Propulsion Laboratory

|access-date = 30 October 2018}}

{{cite web

|title = 162173 Ryugu (1999 JU3)

|work = Minor Planet Center

|url = https://www.minorplanetcenter.net/db_search/show_object?object_id=162173

|access-date = 30 October 2018}}

{{cite web

|title = MPC/MPO/MPS Archive

|work = Minor Planet Center

|url = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html

|access-date = 30 October 2018}}

{{cite press release

|title = Name Selection of Asteroid 1999 JU3 Target of the Asteroid Explorer "Hayabusa2"

|publisher = JAXA

|date = 5 October 2015

|url = http://global.jaxa.jp/press/2015/10/20151005_ryugu.html

|access-date = 30 October 2018}}

{{cite web

|title = Current status of the asteroid explorer, Hayabusa2, leading up to arrival at asteroid Ryugu in 2018

|date = 14 June 2016

|publisher = JAXA

|url = http://global.jaxa.jp/projects/sat/hayabusa2/pdf/Hayabusa2_Press20180614e.pdf

|access-date = 30 October 2018}}

{{cite web

|title = From a distance of about 700km, Ryugu's rotation was observed

|date = 16 June 2016

|publisher = JAXA

|url = http://www.hayabusa2.jaxa.jp/topics/20180616je/index_e.html

|access-date = 30 October 2018}}

{{citation

|title = Operation status for the asteroid explorer, Hayabusa2, in the vicinity of Ryugu

|date = 5 September 2018

|publisher = JAXA

|url = http://global.jaxa.jp/projects/sat/hayabusa2/pdf/20180905_hayabusa2_e.pdf

|access-date = 30 October 2018}}

{{cite web

|last1 = Yoshimitsu |first1=Tetsuo

|last2 = Kubota |first2=Takashi

|last3 = Tsuda |first3=Yuichi

|last4 = Yoshikawa |first4=Makoto

|title = MINERVA-II1: Successful image capture, landing on Ryugu and hop!

|publisher = JAXA

|date = 23 September 2015

|url = http://www.hayabusa2.jaxa.jp/en/topics/20180922e/

|website = JAXA Hayabusa2 Project

|access-date = 30 October 2018}}

{{cite web

|last1 = Clark |first1=Stephen

|title = Hayabusa 2 team sets dates for asteroid landings – Spaceflight Now

|date = 6 September 2018

|url = https://spaceflightnow.com/2018/09/06/hayabusa-2-team-sets-dates-for-asteroid-landings/

|website = spaceflightnow.com

|access-date = 7 September 2018}}

{{cite web

|last1 = Wall |first1 = Mike

|title = Japanese Probe Deploys Tiny Hopping Robots Toward Big Asteroid Ryugu

|date = 21 September 2018

|url = https://www.space.com/41898-hayabusa2-deploys-hopping-robots-asteroid-ryugu.html

|website = space.com

|access-date = 30 October 2018}}

{{cite web

|title = Touchdown! Japan space probe lands new robot on asteroid

|date = 3 October 2018

|website = phys.org

|url = https://phys.org/news/2018-10-japanese-spacecraft-device-asteroid.html

|access-date = 30 October 2018}}

{{cite web

|last1 = Plait |first1 = Phil

|title = Asteroid Ryugu Starts to Come Into Focus

|date = 20 June 2018

|publisher = SyFy Wire

|url = https://www.syfy.com/syfywire/asteroid-ryugu-starts-to-come-into-focus

|access-date = 30 October 2018}}

{{Cite conference

|display-authors = 6

|first1 = M. |last1 = Abe

|first2 = K. |last2 = Kawakami

|first3 = S. |last3 = Hasegawa

|first4 = D. |last4 = Kuroda

|first5 = M. |last5 = Yoshikawa

|first6 = T. |last6 = Kasuga

|first7 = K. |last7 = Kitazato

|first8 = Y. |last8 = Sarugaku

|first9 = D. |last9 = Kinoshita

|first10 = S. |last10 = Miyasaka

|first11 = S. |last11 = Urakawa

|first12 = S. |last12 = Okumura

|first13 = Y. |last13 = Takagi

|first14 = N. |last14 = Takato

|first15 = T. |last15 = Fujiyoshi

|first16 = H. |last16 = Terada

|first17 = T. |last17 = Wada

|first18 = Y. |last18 = Ita

|first19 = F. |last19 = Vilas

|first20 = R. P. |last20 = Weissman

|date = March 2008

|title = Ground-based Observational Campaign for Asteroid 162173 1999 JU3

|url = https://www.lpi.usra.edu/meetings/lpsc2008/pdf/1594.pdf

|journal = Lunar and Planetary Science

|issue = 1391 |conference = 37th COSPAR Scientific Assembly

|page = 1594

|bibcode = 2008LPI....39.1594A

|access-date= 30 October 2018}}

{{Cite journal

|display-authors = 6

|first1 = T. G. |last1 = Müller

|first2 = J. |last2 = Durech

|first3 = M. |last3 = Ishiguro

|first4 = M. |last4 = Mueller

|first5 = T. |last5 = Krühler

|first6 = H. |last6 = Yang

|first7 = M.-J. |last7 = Kim

|first8 = L. |last8 = O'Rourke

|first9 = F. |last9 = Usui

|first10 = C. |last10 = Kiss

|first11 = B. |last11 = Altieri

|first12 = B. |last12 = Carry

|first13 = Y.-J. |last13 = Choi

|first14 = M. |last14 = Delbo

|first15 = J. P. |last15 = Emery

|first16 = J. |last16 = Greiner

|first17 = S. |last17 = Hasegawa

|first18 = J. L. |last18 = Hora

|first19 = F. |last19 = Knust

|first20 = D. |last20 = Kuroda

|first21 = D. |last21 = Osip

|first22 = A. |last22 = Rau

|first23 = A. |last23 = Rivkin

|first24 = P. |last24 = Schady

|first25 = J. |last25 = Thomas-Osip

|first26 = D. |last26 = Trilling

|first27 = S. |last27 = Urakawa

|first28 = E. |last28 = Vilenius

|first29 = P. |last29 = Weissman

|first30 = P. |last30 = Zeidler

|date = March 2017

|title = Hayabusa-2 mission target asteroid 162173 Ryugu (1999 JU3): Searching for the object's spin-axis orientation

|journal = Astronomy and Astrophysics

|volume = 599

|page = 25

|bibcode = 2017A&A...599A.103M

|doi = 10.1051/0004-6361/201629134

|arxiv = 1611.05625

|s2cid = 73519172 }}

{{Cite journal

|display-authors = 6

|first1 = Myung-Jin |last1 = Kim

|first2 = Young-Jun |last2 = Choi

|first3 = Hong-Kyu |last3 = Moon

|first4 = Masateru |last4 = Ishiguro

|first5 = Stefano |last5 = Mottola

|first6 = Murat |last6 = Kaplan

|first7 = Daisuke |last7 = Kuroda

|first8 = Dhanraj S. |last8 = Warjurkar

|first9 = Jun |last9 = Takahashi

|first10 = Yong-Ik |last10 = Byun

|date = February 2013

|title = Optical observations of NEA 162173 (1999 JU3) during the 2011–2012 apparition

|journal = Astronomy and Astrophysics

|volume = 550

|page = 4

|bibcode = 2013A&A...550L..11K

|doi = 10.1051/0004-6361/201220673

|arxiv = 1302.4542

|s2cid = 54684944 }}

{{Cite journal

|display-authors = 6

|first1 = S. |last1 = Hasegawa

|first2 = T. G. |last2 = Müller

|first3 = K. |last3 = Kawakami

|first4 = T. |last4 = Kasuga

|first5 = T. |last5 = Wada

|first6 = Y. |last6 = Ita

|first7 = N. |last7 = Takato

|first8 = H. |last8 = Terada

|first9 = T. |last9 = Fujiyoshi

|first10 = M. |last10 = Abe

|date = December 2008

|title = Albedo, Size, and Surface Characteristics of Hayabusa-2 Sample-Return Target 162173 1999 JU3 from AKARI and Subaru Observations

|journal = Publications of the Astronomical Society of Japan

|volume = 60

|issue = SP2

|pages = S399––S405

|bibcode = 2008PASJ...60S.399H

|doi = 10.1093/pasj/60.sp2.S399

|doi-access= free

}}

{{Cite journal

|display-authors = 6

|first1 = H. |last1 = Campins

|first2 = J. P. |last2 = Emery

|first3 = M. |last3 = Kelley

|first4 = Y. |last4 = Fernández

|first5 = J. |last5 = Licandro

|first6 = M. |last6 = Delbó

|first7 = A. |last7 = Barucci

|first8 = E. |last8 = Dotto

|date = August 2009

|title = Spitzer observations of spacecraft target 162173 (1999 JU3)

|journal = Astronomy and Astrophysics

|volume = 503

|issue = 2

|pages = L17–L20

|bibcode = 2009A&A...503L..17C

|doi = 10.1051/0004-6361/200912374

|arxiv = 0908.0796

|s2cid = 16329091 }}

{{Cite journal

|first1 = Liang-Liang |last1 = Yu

|first2 = Jiang-Hui |last2 = Ji

|first3 = Su |last3 = Wang

|date = July 2014

|title = Investigation of Thermal Inertia and Surface Properties for Near-earth Asteroid (162173) 1999 JU3

|journal = Chinese Astronomy and Astrophysics

|volume = 38

|issue = 3

|pages = 317–329

|bibcode = 2014ChA&A..38..317Y

|doi = 10.1016/j.chinastron.2014.07.008

|arxiv= 1805.05244|s2cid = 119186039

}}

}}

• {{cite journal

| last1=Vilas | first1=F.

| year=2008

| title=Spectral Characteristics of Hayabusa 2 Near-Earth Asteroid Targets 162173 1999 Ju3 and 2001 Qc34

| journal=Astronomical Journal

| volume=135 | issue=4

| pages=1101–1105

| bibcode=2008AJ....135.1101V

| doi=10.1088/0004-6256/135/4/1101

| doi-access=free

}}

• {{cite web

| date=18–20 May 2009

| title=International Symposium Marco Polo and other Small Body Sample Return Missions: Programme and Presentations

| url=http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=43784

| publisher=European Space Agency

}}

• {{Cite journal

| display-authors = 6

| first1 = Nicholas A. |last1 = Moskovitz

| first2 = Shinsuke |last2 = Abe

| first3 = Kang-Shian |last3 = Pan

| first4 = David J. |last4 = Osip

| first5 = Dimitra |last5 = Pefkou

| first6 = Mario D. |last6 = Melita

| first7 = Mauro |last7 = Elias

| first8 = Kohei |last8 = Kitazato

| first9 = Schelte J. |last9 = Bus

| first10 = Francesca E. |last10 = DeMeo

| first11 = Richard P. |last11 = Binzel

| first12 = Paul A. |last12 = Abell

| date = May 2013

| title = Rotational characterization of Hayabusa II target Asteroid (162173) 1999 JU3

| journal = Icarus

| volume = 224

| issue = 1

| pages = 24–31

| bibcode = 2013Icar..224...24M

| doi = 10.1016/j.icarus.2013.02.009

| arxiv = 1302.1199

| s2cid = 118517193 }}

{{Commons category}}

• [http://europlanet.dlr.de/Hayabusa2/MASCOT/index.html MASCOT related publications by the Institute of Planetary Research] contains related images and 3D models of the surface of Ryugu
• {{NeoDys|162173}}
• {{ESA-SSA|162173|Ryugu}}
• {{JPL small body|id=162173}}

{{Minor planets navigator | |number=162173 | }}

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Category:Named minor planets

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