Computer Science – Sound
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p23a1608f&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P23A-1608
Computer Science
Sound
[0629] Electromagnetics / Inverse Scattering, [5464] Planetary Sciences: Solid Surface Planets / Remote Sensing, [5470] Planetary Sciences: Solid Surface Planets / Surface Materials And Properties, [6250] Planetary Sciences: Solar System Objects / Moon
Scientific paper
Previous investigations have shown that lunar surface consists of a fine-grained regolith layer that completely covers the underlying bedrock. The lunar regolith is a byproduct of the continuous impact of large and small meteoroids with the lunar surface, and consists largely of fragmented materials and breccias. In general, the thickness of the regolith is an indication of the age of lunar surface: the older the age, the greater the thickness. The regolith contains potentially valuable resources and volatiles (such as ice and helium-3), and all future human activates will use regolith for building materials and shielding. Therefore, knowledge of the regolith layer thickness provides important information about both lunar geology and for future lunar exploration. The regolith thickness over small regions has been estimated previously from direct measurements made during the Apollo missions (such as seismic and multifrequency electromagnetic probing experiments), as well as studies of impact crater morphology and crater size-frequency distributions. From these studies, the average thickness of the regolith is believed to be about 4-5 m in the maria and 10-15 m in the older highland regions. Recently, remote sensing techniques, such as Earth-based radar, Chang-E microwave radiometery, and Kaguya lunar radar sounding, have been used to invert for regolith thickness over large regions. However, the uncertainties in the calibration of these data and the use of a simplified regolith model that did not consider buried rocks have limited the utility of these techniques. In this study, a rigorous radar scattering model based on vector radiative transfer theory and the newly acquired Earth-based 70 cm radar data are used to invert for a much more accurate regolith map for the lunar nearside hemisphere. Three parameters are required for radar studies of the regolith: regolith dielectric permittivity, surface roughness, and subsurface rock size and abundance. Our reinvestigation of the measured dielectric properties of the Apollo samples shows that, when normalized to a constant density (or porosity), the relative permittivity is constant and the loss tangent depends only on the abundance of TiO2. The dielectric permittivity across the lunar surface is then estimated globally using this relation and the regolith composition derived from the Lunar Prospector γ-ray spectrometer. Second, we estimated the surface roughness and abundance of subsurface rocks at the Apollo landing sites, where the regolith thickness and composition are known. Preliminary result shows that, at the scale of 70 cm wavelength, the rms slope of the lunar surface is around 2-10°, and highlands are rougher than the maria. The average population of buried rocks in the regolith is about 0.5 per m3 for effective sizes of 6 cm. Extrapolating these surface roughness and rock abundances globally, we inverted for the regolith thickness using the Earth-based 70 cm opposite sense radar data. Preliminary results show that the regolith thickness of over the maria is smaller than the highlands by at least a factor of 2. The correlation between regolith thickness and lunar surface age is currently being analyzed.
Fa Wei
Wieczorek Mark A.
No associations
LandOfFree
Regolith thickness of the lunar nearside: Preliminary results from Earth-based 70 cm radar observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Regolith thickness of the lunar nearside: Preliminary results from Earth-based 70 cm radar observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Regolith thickness of the lunar nearside: Preliminary results from Earth-based 70 cm radar observations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1495826