A potential subsurface cavity in the continuous ejecta deposits of the Ziwei crater discovered by the Chang’E-3 mission

AbstractIn the radargram obtained by the high-frequency lunar penetrating radar onboard the Chang’E-3 mission, we notice a potential subsurface cavity that has a smaller permittivity compared to the surrounding materials. The two-way travel time between the top and bottom boundaries of the potential cavity is ~ 21 ns, and the entire zone is located within the continuous ejecta deposits of the Ziwei crater, which generally have similar physical properties to typical lunar regolith. We carried out numerical simulations for electromagnetic wave propagation to investigate the nature of this low-permittivity zone. Assuming different shapes for this zone, a comprehensive comparison between our model results and the observed radargram suggests that the roof of this zone is convex and slightly inclined to the south. Modeling subsurface materials with different relative permittivities suggests that the low-permittivity zone is most likely formed due to a subsurface cavity. The maximum vertical dimension of this potential cavity is ~ 3.1 m. While the continuous ejecta deposits of Ziwei crater are largely composed of pre-impact regolith, competent mare basalts were also excavated, which is evident by the abundant meter-scale boulders on the wall and rim of Ziwei crater. We infer that the subsurface cavity is supported by excavated large boulders, which were stacked during the energetic emplacement of the continuous ejecta deposits. However, the exact geometry of this cavity (e.g., the width) cannot be constrained using the single two-dimensional radar profile. This discovery indicates that large voids formed during the emplacement of impact ejecta should be abundant on the Moon, which contributes to the high bulk porosity of the lunar shallow crust, as discovered by the GRAIL mission. Our results further suggest that ground penetrating radar is capable of detecting and deciphering subsurface cavities such as lava tubes, which can be applied in future lunar and deep space explorations.

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Velocity Analysis Using Separated Diffractions for Lunar Penetrating Radar Obtained by Yutu-2 Rover

Remote Sensing ◽

10.3390/rs13071387 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1387

Author(s):

Chao Li ◽

Jinhai Zhang

Keyword(s):

Dielectric Permittivity ◽

Lunar Regolith ◽

Velocity Model ◽

Velocity Estimation ◽

Quality Data ◽

High Quality Data ◽

Shallow Subsurface ◽

Subsurface Structures ◽

Ground Penetrating ◽

Permittivity Model

The high-frequency channel of lunar penetrating radar (LPR) onboard Yutu-2 rover successfully collected high quality data on the far side of the Moon, which provide a chance for us to detect the shallow subsurface structures and thickness of lunar regolith. However, traditional methods cannot obtain reliable dielectric permittivity model, especially in the presence of high mix between diffractions and reflections, which is essential for understanding and interpreting the composition of lunar subsurface materials. In this paper, we introduce an effective method to construct a reliable velocity model by separating diffractions from reflections and perform focusing analysis using separated diffractions. We first used the plane-wave destruction method to extract weak-energy diffractions interfered by strong reflections, and the LPR data are separated into two parts: diffractions and reflections. Then, we construct a macro-velocity model of lunar subsurface by focusing analysis on separated diffractions. Both the synthetic ground penetrating radar (GPR) and LPR data shows that the migration results of separated reflections have much clearer subsurface structures, compared with the migration results of un-separated data. Our results produce accurate velocity estimation, which is vital for high-precision migration; additionally, the accurate velocity estimation directly provides solid constraints on the dielectric permittivity at different depth.

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Inorganic-Organic Composites (Ormocers) as Structured Layers for Microelectronics

MRS Proceedings ◽

10.1557/proc-180-995 ◽

1990 ◽

Vol 180 ◽

Cited By ~ 24

Author(s):

Michael Popall ◽

Henning Meyer ◽

Helmut Schmidt ◽

Jochen Schulz

Keyword(s):

System Integration ◽

Signal Transmission ◽

Sol Gel ◽

Unsaturated Hydrocarbon ◽

Direct Laser ◽

Organically Modified ◽

Integration Techniques ◽

Edge Quality ◽

Low Permittivity ◽

High Bulk

ABSTRACTEnhanced integration, faster signal transmission and reduced size of mounting devices in components for microelectronics requires new patternable materials. Inorganic-organic copolymers (ORMOCERs = ORganically MOdified CERamics), prepared by sol-gel techniques have been developed for interconnection technologies in microelectronics. Photopolymerization is enabled by unsaturated hydrocarbon or epoxide substituents and UV-sensitive initiators. Using a frequency doubled Argonion laser at 257 nm for direct laser writing, patterned layers with high edge quality have been realized. In combination with high breakthrough voltages, low permittivity constants and high bulk resistivities they open interesting aspects for very large system integration techniques (VLSI).

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Mapping the structure and depth of lava tubes using ground penetrating radar

Geophysical Research Letters ◽

10.1029/2005gl024159 ◽

2005 ◽

Vol 32 (21) ◽

Cited By ~ 15

Author(s):

Hideaki Miyamoto ◽

Jun'ichi Haruyama ◽

Takao Kobayashi ◽

Keiiti Suzuki ◽

Tatsuaki Okada ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Lava Tubes ◽

Ground Penetrating

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Resolution of Lava Tubes With Ground Penetrating Radar: The TubeX Project

Journal of Geophysical Research Planets ◽

10.1029/2019je006138 ◽

2020 ◽

Vol 125 (5) ◽

Cited By ~ 3

Author(s):

S. Esmaeili ◽

S. Kruse ◽

S. Jazayeri ◽

P. Whelley ◽

E. Bell ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Lava Tubes ◽

Ground Penetrating

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Coating and Characterization of Mock and Explosive Materials

Advances in Materials Science and Engineering ◽

10.1155/2012/468032 ◽

2012 ◽

Vol 2012 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Emily M. Hunt ◽

Matt Jackson

Keyword(s):

Energetic Materials ◽

Energetic Material ◽

Precision Control ◽

Explosive Materials ◽

Coated Materials ◽

Air Stream ◽

High Bulk Density ◽

Comprehensive Comparison ◽

High Bulk

This project develops a method of manufacturing plastic-bonded explosives by using use precision control of agglomeration and coating of energetic powders. The energetic material coating process entails suspending either wet or dry energetic powders in a stream of inert gas and contacting the energetic powder with atomized droplets of a lacquer composed of binder and organic solvent. By using a high-velocity air stream to pneumatically convey the energetic powders and droplets of lacquer, the energetic powders are efficiently wetted while agglomerate drying begins almost immediately. The result is an energetic powder uniformly coated with binder, that is, a PBX, with a high bulk density suitable for pressing. Experiments have been conducted using mock explosive materials to examine coating effectiveness and density. Energetic materials are now being coated and will be tested both mechanically and thermally. This allows for a comprehensive comparison of the morphology and reactivity of the newly coated materials to previously manufactured materials.

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Characterization of Subsurface Cavities using Gravity and Ground Penetrating Radar

Journal of Environmental and Engineering Geophysics ◽

10.2113/jeeg24.2.265 ◽

2019 ◽

Vol 24 (2) ◽

pp. 265-276

Author(s):

Fathi M.S. Abdullah ◽

Abdullatif A. Al-Shuhail ◽

Oluseun A. Sanuade

Keyword(s):

Ground Penetrating Radar ◽

Water Saturation ◽

Gravity Data ◽

Rock Physics ◽

Human Action ◽

Data Sets ◽

Filling Materials ◽

Gravity Measurements ◽

Ground Penetrating ◽

Subsurface Cavities

Subsurface cavities occur naturally by dissolution of carbonates and evaporites or by human action, such as the construction of tunnels and tombs. They can be filled with air, water, sediments, or a combination. Gravity and ground penetrating radar (GPR) methods have been used widely to determine the location and size of subsurface cavities. The objective of this study is to present a quantitative approach to estimate the porosity and water saturation of cavity-filling materials from GPR and gravity measurements. The approach uses appropriate rock-physics models of the dielectric permittivity and density of a shallow cavity and estimates the porosity and water saturation inside the cavity by solving the two model equations simultaneously for these two variables. We test the proposed method using synthetic GPR and gravity data sets corresponding to three spherical-cavity models: air-filled, water-filled, and a partially-saturated sand filling. Results show that the method is accurate in retrieving the correct porosity within 0.76% error and water saturation within 2.4% error. We also apply the method on three published case studies over air-filled rectangular cavities. We found that the proposed method estimated the correct porosity and water saturation in one study but failed with the other studies. However, when the procedure was repeated with gravity values calculated from parameters reported in these studies, the proposed method estimated the correct porosity and water saturation accurately.

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