Impact crater related surficial deposits on Venus: Multipolarization radar observations with Arecibo
نویسندگان
چکیده
[1] The distribution of surficial deposits in the vicinity of impact craters on Venus was studied using measurements of the polarization properties of the reflected radar wave. Subsurface scattering of an incident circularly polarized radar signal results in a linearly polarized component in the radar echo due to the differing transmission coefficients at a smooth (at wavelength scales) atmosphere-surface boundary for the horizontal (H) and vertical (V) linearly polarized components of the incident wave. Arecibo 12.6 cm wavelength radar observations in 1999 and 2001 provided images of the surface of Venus in the full Stokes polarization parameters of the reflected echo, from which images in the degree of linear polarization were derived. These images show that substantial areas of Sedna, Guinevere, and Lavinia Planitias return a radar echo with a significant degree of linear polarization, indicating that mantling deposits may be relatively widespread on the plains of Venus. The areas showing linear polarization enhancements are strongly correlated with topographic features, primarily impact craters, dome fields, and windblown deposits, including dune fields. A strong linearly polarized echo component ( 10–40% linear polarization) is found from regions near 45 impact craters, including 5 parabolas. These linear polarization features typically correspond to diffuse, higher backscatter cross-section (bright) regions in Magellan images. The linearly polarized component in these regions is attributed to subsurface echoes from a mantled substrate or from buried rocks.
منابع مشابه
Searching for Surficial Deposits on Venus Using Multi-polarization Radar
Introduction. The Magellan spacecraft returned hundreds of images of craters, radar-dark halos, and wind features on Venus. It is clear that surficial layers are associated with some of these features; for example, 59 of the craters have parabolic shaped deposits that are thought to be a few centimeters to a meter in thickness [1],[2]. Magellan also revealed about 400 radar dark “splotches” tha...
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