Computer Science – Sound
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p13b1282b&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P13B-1282
Computer Science
Sound
[0702] Cryosphere / Permafrost, [5460] Planetary Sciences: Solid Surface Planets / Physical Properties Of Materials, [5494] Planetary Sciences: Solid Surface Planets / Instruments And Techniques, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
Subsurface water on Mars has been subject to several hypothesis and debates. To access its potential distribution and state in the fractured Martian subsurface, two low-frequency radar sounders (MARSIS and SHARAD) are currently probing the Martian upper crust exploring dielectric evidence of volatiles presence. The identification of volatiles signatures using low frequency radars is constrained by our understanding of both dielectric and scattering losses mechanisms that are generated by the dielectric complexity and the heterogeneities of the Martian subsurface. Both of those parameters remain unfortunately poorly quantified in planetary analog environments. To address this issue, we conducted wide-band ground penetrating radar (GPR) investigations and resistivity survey on a permafrost terrain, at the Vault Creek located 21 km North of Fairbanks (Alaska, USA). The site presents a 40 m deep mining tunnel, which allows validating the subsurface composition and the different geologic interfaces as inferred from the radar echoes. The area shows several geomorphological and geophysical analogies to recently observed terrains in the high and mid-latitudes on Mars (e.g. permafrost, ground polygons and pingoos). The GPR surveys were performed at four central frequencies (40, 270, 400 and 900 MHz) along the same profile in order to monitor the attenuation mechanisms over the 40 to 900 MHz frequency band. The obtained data set provided an insight into characterizing and quantifying the different frequency-dependant loss mechanisms (mainly scattering and dielectric attenuation) that occur on the radar signal in permafrost. Scattering was found to dominate the overall observed attenuation starting 100 MHz and increased with frequency. Preliminary results suggest that the scattering losses are of 0.58dB/m at 270MHz compared to 0.80dB/m at 900MHz. Dielectric losses showed less frequency dependence than the scattering ones. The output of this study aims to constrain the ambiguities associated to the interpretation of MARSIS and SHARAD radar data. This work is support by the NASA Mars Fundamental Research Program.
Anglade André
Boisson Joséphine
Clifford Stephen M.
Heggy Essam
Yoshikawa Kenichi
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