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Characterization of the Ryugu surface by means of the variability of the near-infrared spectral slope in NIRS3 data

Galiano, Anna and Palomba, E. and D'Amore, Mario and Zinzi, A. and Dirri, Fabrizio and Longobardo, Andrea and Kitazato, K. and Iwata, T. and Matsuoka, M. and Hiroi, T. (2020) Characterization of the Ryugu surface by means of the variability of the near-infrared spectral slope in NIRS3 data. Icarus: International Journal of Solar System Studies, 351, p. 113959. Elsevier. doi: 10.1016/j.icarus.2020.113959. ISSN 0019-1035.

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Official URL: https://www.sciencedirect.com/science/article/abs/pii/S0019103520303328


The Near-Earth Asteroid 162173 Ryugu (1999 JU3) was investigated by the JAXA Hayabusa2 mission from June 2018 to November 2019. The data acquired by NIRS3 spectrometer revealed a dark surface with a positive near-infrared spectral slope. In this work we investigated the spectral slope variations across the Ryugu surface, providing information about physical/chemical properties of the surface. We analysed the calibrated, thermally and photometrically corrected NIRS3 data, and we evaluated the spectral slope between 1.9 um and 2.5 um, whose values extend from 0.11 to 0.28 and the mean value corresponds to 0.163+-0.022. Starting from the mean value of slope and moving in step of 1 standard deviation (0.022), we defined 9 “slope families”, the Low-Red-Slope families (LR1, LR2 and LR3) and the High-Red-Sloped families (HR1, HR2, HR3, HR4, HR5, HR6). The mean values of some spectral parameters were estimated for each family, such as the reflectance factor at 1.9 um, the spectral slope, the depth of bands at 2.7 um and at 2.8 um. A progressive spectral reddening, darkening and weakening/narrowing of OH bands is observed moving from the LR families to the HR families. We concluded that the spectral variability observed among families is the result of the thermal metamorphism experienced by Ryugu after the catastrophic disruption of its parent body and space weathering processes that occurred on airless bodies as Ryugu, such as impact cratering and solar wind irradiation. As a consequence, the HR1, LR1, LR2 and LR3 families, corresponding to equatorial ridge and crater rims, are the less altered regions on Ryugu surface, which experienced the minor alteration and OH devolatilization; the HR2, HR3, HR4, HR5 families, coincident with floors and walls of impact craters, are the most altered areas, result of the three processes occurring on Ryugu. The strong reddening of the HR6 family (coincident with Ejima Saxum) is likely due to the fine-sized material covering the large boulder.

Item URL in elib:https://elib.dlr.de/138404/
Document Type:Article
Title:Characterization of the Ryugu surface by means of the variability of the near-infrared spectral slope in NIRS3 data
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Galiano, AnnaIAPS - Istituto di Astrofisica e Planetologia Spaziali, INAF - Istituto Nazionale di Astrofisica, Rome, ItalyUNSPECIFIED
D'Amore, MarioMario.DAmore (at) dlr.dehttps://orcid.org/0000-0001-9325-6889
Dirri, FabrizioINAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Via del Fosso del Cavaliere, 100, 00133 Rome, ItalyUNSPECIFIED
Longobardo, AndreaINAF Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere, 00133 Rome, ItalyUNSPECIFIED
Kitazato, K.Institute of Space and Astronautical Science , Japan Aerospace Exploration Agency (ISAS / JAXA) ( 3 - 1 - 1 Yoshinodai, Chuo - Ku, Sa gamihara 2 52 - 5210 , JapanUNSPECIFIED
Iwata, T.Japan Aerospace Exploration Agency (JAXA), Sagamihara, JapanUNSPECIFIED
Matsuoka, M.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS / JAXA) 3-1-1 Yoshinodai, Chuo-Ku, Sagamihara 252-5210, JapanUNSPECIFIED
Hiroi, T.Brown University, Providence, RI, USAUNSPECIFIED
Journal or Publication Title:Icarus: International Journal of Solar System Studies
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.icarus.2020.113959
Page Range:p. 113959
Keywords:Ryugu Near-earth asteroid Hayabusa2 Space weathering NIR spectral slope
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Space Exploration
DLR - Research theme (Project):R - Project BepiColombo - MERTIS and BELA
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Planetary Research > Planetary Laboratories
Deposited By: Amore, Dr. Mario
Deposited On:27 Nov 2020 10:55
Last Modified:27 Nov 2020 10:55

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