In situ lunar phase curves measured by Chang’E-4 in the Von Kármán Crater, South Pole-Aitken basin

¹ Planetary Science Institute, School of Earth Sciences, China University of Geosciences, Wuhan, PR China
e-mail: zhanghao@cug.edu.cn
² CAS Center for Excellence in Comparative Planetology, Hefei, PR China
³ Key Laboratory of Lunar and Deep Space Exploration, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, PR China
e-mail: liudw@nao.cas.cn
⁴ Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an, PR China
⁵ Department of Physics & Astronomy, The University of Alabama, Tuscaloosa, AL, USA
⁶ State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa, Macau
⁷ Beijing Institute of Space Mechanics and Electronics, China Academy of Space Technology, Beijing, PR China

Received: 25 August 2020
Accepted: 1 December 2020

Abstract

Context. The Yutu-2 rover of the Chang’E-4 (CE-4) mission measured the lunar phase curves in the Von Kármán crater, South Pole-Aitken basin.

Aims. We aim to study the photometric properties of the regolith at CE-4’s landing site and compare them with those of Chang’E-3 (CE-3) in order to understand the regolith physical properties of the two landing sites.

Methods. We extracted the insitu lunar phase curves measured by CE-4 with a very wide phase angle coverage (1°–144°) and performed photometric model inversions using both the Hapke model and the Lumme-Bowell model.

Results. Compared with the CE-3 measurement taken in Mare Imbrium, the CE-4 phase curves show the colorimetric opposition effect and have a steeper and narrower opposition spike. The surface regolith at the CE-4 site is much darker, more porous, more forward scattering, and has a larger slope angle (Hapke model) than that of CE-3.

Conclusions. The CE-4 site may have experienced more space weathering alterations than the CE-3 site, which is consistent with their different surface model ages (~3.6 Ga for CE-4 and ~3 Ga for CE-3).