Granular avalanches on the Moon: Mass‐wasting conditions, processes, and features
61
Citation
138
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract Seven lunar crater sites of granular avalanches are studied utilizing high‐resolution images (0.42–1.3 m/pixel) from the Lunar Reconnaissance Orbiter Camera; one, in Kepler crater, is examined in detail. All the sites are slopes of debris extensively aggraded by frictional freezing at their dynamic angle of repose, four in craters formed in basaltic mare and three in the anorthositic highlands. Diverse styles of mass wasting occur, and three types of dry‐debris flow deposit are recognized: (1) multiple channel‐and‐lobe type, with coarse‐grained levees and lobate terminations that impound finer debris, (2) single‐surge polylobate type, with subparallel arrays of lobes and fingers with segregated coarse‐grained margins, and (3) multiple‐ribbon type, with tracks reflecting reworked substrate, minor levees, and no coarse terminations. The latter type results from propagation of granular erosion‐deposition waves down slopes dominantly of fine regolith, and it is the first recognized natural example. Dimensions, architectures, and granular segregation styles of the two coarse‐grained deposit types are like those formed in natural and experimental avalanches on Earth, although the timescale of motion differs due to the reduced gravity. Influences of reduced gravity and fine‐grained regolith on dynamics of granular flow and deposition appear slight, but we distinguish, for the first time, extensive remobilization of coarse talus by inundation with finer debris. The (few) sites show no clear difference attributable to the contrasting mare basalt and highland megaregolith host rocks and their fragmentation. This lunar study offers a benchmarking of deposit types that can be attributed to formation without influence of liquid or gas.Keywords:
Regolith
Mass wasting
Angle of repose
Lunar mare
Debris flow
Simultaneous observations of Lunar Radar Sounder (LRS) and Laser ALTimeter (LALT) of Kaguya, a Japanese lunar exploration project, were carried out for the purpose of mapping regolith layer thickness of the Moon. Nadir surface echo of a high-frequency (5 MHz) pulse of LRS interferes the shallow (<; 10 m) subsurface echo from the bottom of the regolith layer, which subsequently makes the apparent surface be detected at a range deviated from the actual surface range, while the actual surface range is optically detected by LALT. Regolith layer thickness information is retrieved from this range difference after an inversion process. So far, four major maria on the near side of the Moon (Maria Tranquillitatis, Serenitatis, Imbrium, and Oceanus Procellarum) have been investigated, and the mean regolith layer thicknesses of the four maria were found to be about the same, ranging from 6.3 to 6.9 m. However, spatial distribution of areal regolith thickness appears different in eastern maria from western maria, which implies a difference of the growth history of the regolith layer.
Regolith
Lunar mare
Nadir
Cite
Citations (39)
Regolith
Lunar mare
Lunar soil
Cite
Citations (8)
Regolith
Lunar mare
Lunar orbit
Lunar soil
Cite
Citations (50)
Lunar penetrating radar (LPR) is an important way to evaluate the geological structure of the subsurface of the moon. The Chang'E-3 has utilized LPR, which is equipped on the lunar rover named Yutu, to obtain the shallow lunar regolith structure in Mare Imbrium. The previous result provides a unique opportunity to map the subsurface structure and vertical distribution of the lunar regolith with high resolution. In order to evaluate the LPR data, the study of lunar regolith media is of great significance for understanding the material composition of the lunar regolith structure. In this letter, we focus on the lunar regolith quantitative random model and parameter inversion with LPR synthetic data. First, based on the Apollo drilling core data, we build the lunar regolith quantitative random model with clipped Gaussian random field theory. It can be used to model the discrete-valued random field with a given correlation structure. Then, we combine radar wave impedance and stochastic inversion methods to carry out LPR data inversion and parameter estimation. The results mostly provide reliable information on the lunar regolith layer structure and local details with high resolution. This letter presents a further research strategy for lunar probe and deep-space detection with LPR.
Regolith
Lunar mare
Lunar soil
Cite
Citations (23)
Regolith
Angle of repose
Particle (ecology)
Lunar soil
Cite
Citations (3)
Regolith
Lunar mare
Lunar soil
Cite
Citations (13)
Regolith
Lunar mare
Outgassing
Lunar soil
Cite
Citations (52)