Issue |
A&A
Volume 666, October 2022
|
|
---|---|---|
Article Number | A185 | |
Number of page(s) | 6 | |
Section | Planets and planetary systems | |
DOI | https://doi.org/10.1051/0004-6361/202244097 | |
Published online | 25 October 2022 |
Photometric behavior of Ryugu’s NIR spectral parameters
1
INAF-IAPS,
Rome, Italy
e-mail: andrea.longobardo@inaf.it
2
ASI-SSDC,
Rome, Italy
3
German Aerospace Center, Institute of Planetary Research,
Berlin, Germany
4
PSI,
Tucson, AZ, USA
5
University of Aizu,
Aizu-Wakamatsu
965-8580,
Fukushima, Japan
6
ISAS-JAXA,
3-1-1 Yoshino-dai, Chuo-ku, Sagamihara,
Kanagawa, Japan
7
Department of Earth, Environmental and Planetary Sciences, Brown University,
Providence, RI
02912, USA
8
Jacobs/NASA Johnson Space Center,
USA
9
Tohoku University,
Miyagi, Japan
10
Kwansei Gakuin University,
Hyogo, Japan
11
Nagoya University,
Nagoya
464-8601, Japan
12
Kobe University,
Kobe
657-8501, Japan
13
National Astronomical Observatory of Japan,
Mitaka
181-8588, Japan
Received:
23
May
2022
Accepted:
22
August
2022
Context. JAXA’s Hayabusa2 mission rendezvoused the Ryugu asteroid for 1.5 years to clarify the carbonaceous asteroids’ record for Solar System origin and evolution.
Aims. We studied the photometric behavior of the spectral parameters characterizing the near-infrared (NIR) spectra of Ryugu provided by the Hayabusa2/NIRS3 instrument, that is to say 1.9 µm reflectance, 2.7 and 2.8 µm band depths (ascribed to phyllosilicates), and NIR slope.
Methods. For each parameter, we applied the following empirical approach: (1) retrieval of the equigonal albedo by applying the Akimov disk function (this step was only performed for the reflectance photometric correction); (2) retrieval of the median spectral parameter value at each phase angle bin; and (3) retrieval of the phase function by a linear fit.
Results. Ryugu’s phase function shows a steepness similar to Ceres, according to the same taxonomy of the two asteroids. Band depths decrease with increasing phase angle: this trend is opposite to that observed on other asteroids explored by space missions and is ascribed to the very dark albedo. NIR and visible phase reddening are similar, contrary to other asteroids, where visible phase reddening is larger: this could be due to surface darkness or to particle smoothness. Albedo and band depths are globally uncorrelated, but locally anticorrelated. A correlation between darkening and reddening is observed.
Key words: minor planets, asteroids: general / minor planets, asteroids: individual: Ryugu / methods: data analysis / techniques: photometric / techniques: spectroscopic
© A. Longobardo et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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