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Characterization of the Ryugu surface by means of the variability of the near-infrared spectral slope in NIRS3 data
- Source :
- Icarus. 351:113959
- Publication Year :
- 2020
- Publisher :
- Elsevier BV, 2020.
-
Abstract
- 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 μm and 2.5 μm, 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 μm, the spectral slope, the depth of bands at 2.7 μm and at 2.8 μm. 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.
- Subjects :
- geography
geography.geographical_feature_category
010504 meteorology & atmospheric sciences
Near-infrared spectroscopy
Mineralogy
Astronomy and Astrophysics
01 natural sciences
Space weathering
Standard deviation
Parent body
Impact crater
Space and Planetary Science
Asteroid
Ridge
0103 physical sciences
Spectral slope
010303 astronomy & astrophysics
Ryugu Near-earth asteroid Hayabusa2 Space weathering NIR spectral slope
Geology
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 00191035
- Volume :
- 351
- Database :
- OpenAIRE
- Journal :
- Icarus
- Accession number :
- edsair.doi.dedup.....7385da033064c98b0cdcb67eee47d2b6