Kitazato, K.K.KitazatoMilliken, R. E.R. E.MillikenIwata, T.T.IwataAbe, M.M.AbeOhtake, M.M.OhtakeMatsuura, S.S.MatsuuraTakagi, Y.Y.TakagiNakamura, T.T.NakamuraHiroi, T.T.HiroiMatsuoka, M.M.MatsuokaRiu, L.L.RiuTsuda, Y.Y.TsudaNakauchi, Y.Y.NakauchiTsumura, K.K.TsumuraArai, T.T.AraiSenshu, H.H.SenshuHirata, N.N.HirataBarucci, M. A.M. A.BarucciBrunetto, R.R.BrunettoPilorget, C.C.PilorgetPoulet, F.F.PouletBibring, J. -P.J. -P.BibringDomingue, D. L.D. L.DomingueVilas, F.F.VilasTakir, D.D.TakirPALOMBA, ErnestoErnestoPALOMBAGaliano, A.A.GalianoPERNA, DavideDavidePERNAOsawa, T.T.OsawaKomatsu, M.M.KomatsuNakato, A.A.NakatoArai, T.T.AraiTakato, N.N.TakatoMatsunaga, T.T.MatsunagaArakawa, M.M.ArakawaSaiki, T.T.SaikiWada, K.K.WadaKadono, T.T.KadonoImamura, H.H.ImamuraYano, H.H.YanoShirai, K.K.ShiraiHayakawa, M.M.HayakawaOkamoto, C.C.OkamotoSawada, H.H.SawadaOgawa, K.K.OgawaIijima, Y.Y.IijimaSugita, S.S.SugitaHonda, R.R.HondaMorota, T.T.MorotaKameda, S.S.KamedaTatsumi, E.E.TatsumiCho, Y.Y.ChoYoshioka, K.K.YoshiokaYokota, Y.Y.YokotaSakatani, N.N.SakataniYamada, M.M.YamadaKouyama, T.T.KouyamaSuzuki, H.H.SuzukiHonda, C.C.HondaNamiki, N.N.NamikiMizuno, T.T.MizunoMatsumoto, K.K.MatsumotoNoda, H.H.NodaIshihara, Y.Y.IshiharaYamada, R.R.YamadaYamamoto, K.K.YamamotoYoshida, F.F.YoshidaAbe, S.S.AbeHiguchi, A.A.HiguchiYamamoto, Y.Y.YamamotoOkada, T.T.OkadaShimaki, Y.Y.ShimakiNoguchi, R.R.NoguchiMiura, A.A.MiuraHirata, N.N.HirataTachibana, S.S.TachibanaYabuta, H.H.YabutaIshiguro, M.M.IshiguroIkeda, H.H.IkedaTakeuchi, H.H.TakeuchiShimada, T.T.ShimadaMori, O.O.MoriHosoda, S.S.HosodaTsukizaki, R.R.TsukizakiSoldini, S.S.SoldiniOzaki, M.M.OzakiTerui, F.F.TeruiOgawa, N.N.OgawaMimasu, Y.Y.MimasuOno, G.G.OnoYoshikawa, K.K.YoshikawaHirose, C.C.HiroseFujii, A.A.FujiiTakahashi, T.T.TakahashiKikuchi, S.S.KikuchiTakei, Y.Y.TakeiYamaguchi, T.T.YamaguchiNakazawa, S.S.NakazawaTanaka, S.S.TanakaYoshikawa, M.M.YoshikawaWatanabe, S.S.Watanabe2025-03-242025-03-2420212397-3366http://hdl.handle.net/20.500.12386/36931Analyses of meteorites and theoretical models indicate that some carbonaceous near-Earth asteroids may have been thermally altered due to radiative heating during close approaches to the Sun<SUP>1-3</SUP>. However, the lack of direct measurements on the subsurface doesn't allow us to distinguish thermal alteration due to radiative heating from parent-body processes. In April 2019, the Hayabusa2 mission successfully completed an artificial impact experiment on the carbonaceous near-Earth asteroid (162173) Ryugu<SUP>4,5</SUP>, which provided an opportunity to investigate exposed subsurface material and test potential effects of radiative heating. Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. The strength and shape of the OH feature suggests that the subsurface material experienced heating above 300 °C, similar to the surface. In contrast, thermophysical modelling indicates that radiative heating cannot increase the temperature above 200 °C at the estimated excavation depth of 1 m, even at the smallest heliocentric distance possible for Ryugu. This supports the hypothesis that primary thermal alteration occurred on Ryugu's parent body.ELETTRONICOenArticle10.1038/s41550-020-01271-22-s2.0-85098752005https://www.nature.com/articles/s41550-020-01271-2https://api.elsevier.com/content/abstract/scopus_id/850987520052021NatAs...5..246KFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation