Low‐frequency radar sounding investigations of the North Amargosa Desert, Nevada: A potential analog of conductive subsurface environments on Mars

Abstract

[1] Theoretical estimates of low-frequency radar sounding performance and its potential for mapping moist subsurface interfaces in conductive environments on Mars are controversial, with predictions of ultimate penetration depth ranging from a few meters to kilometers. To address this issue, we conducted a broadband electromagnetic field survey in which we combined ground penetrating radar (GPR) operating at multiple low frequencies with the transient electromagnetic method (TEM) to investigate the dependence of radar penetration depth on ground resistivity. Surveys were performed in the frequency range 16-100 MHz at two locations on the northwest margin of the Amargosa Desert, Nevada, where numerous Mars-analog investigations have been performed. The surveys were conducted on a 20-m-high homogenous sand dune and on the flanks of a 20-m-high scoria cone and above a buried lava flow. A wet alluvial interface was located at the bottom of each structure. GPR detected the wet alluvium contact at the base of the sand dune, but failed to penetrate to the same depth at the scoria cone under similar residual moisture content. Depths of investigation for both the scoria cone and the buried lava flow were limited to approximately 10 m owing to the presence of conductive inclusions in the first few meters, which are below the radar resolution but dramatically decreased the dynamic of the radar-backscattered echoes and hence the penetration depth. Absorption models constrained by the TEM data are in good agreement with these observations. Depths of investigation varied weakly with frequency owing to substantial, frequency-independent absorption.

The internal structure of modern barchan dunes of the Ebro River Delta (Spain) from ground penetrating radar

“…GPR has been used to examine the internal structures of aeolian sedimentary deposits such as ancient sand dunes (Harari, 1996) and more recently, Holocene dunes and dunefields (Bristow et al, 2000;Bristow et al, 2005;Pedersen and Clemmensen, 2005;Bristow and Pucillo, 2006;Costas et al, 2006;Heggy et al, 2006). GPR response of sand dunes of aeolian origin has been analyzed in this study in order to: characterize their internal architecture, determine their development and recent evolution, and calculate electromagnetic (EM) waves mean velocities in fine-grained sedimentary deposits.…”

Radar sounding of temperate permafrost in Alaska: Analogy to the Martian midlatitude to high-latitude ice-rich terrains

“…To better constrain those results, analog terrains need to be investigated to well characterize the radar signal behavior on an ice‐rich environment. Although some GPR surveys have investigated these properties in Mars‐analog volcanic terrains [ Paillou et al , 2001; Grant et al , 2004; Grimm et al , 2006; Heggy et al , 2006a, 2006b] and permafrost terrains [ Arcone et al , 2002; Leuschen et al , 2003; Yoshikawa et al , 2006], the complexity of the different loss mechanisms remains poorly constrained.…”

Absorption and scattering in ground‐penetrating radar: Analysis of the Bishop Tuff

“…Data were recorded at 4–16 scans/sec, so at an average speed of 0.5 m/s, the single‐pulse station spacing was 0.031–0.125 m. Therefore MLF data density is ∼16 scans/m, a difference of 12 dB from the density acquired with the PE. All together, our field experience indicates that the effective dynamic range available for all ground losses averages ∼105 dB for the PE and ∼85 dB for the MLF [see also Heggy et al , 2006b]. Each MLF profile was repeated for each site, however, and the better selected for interpretation.…”

“…We have undertaken a multiinstitutional, multiyear campaign to better define and investigate Mars geophysical analogs, particularly with GPR in the 10–100 MHz range. This report, and two companion papers [ Heggy et al , 2006a, 2006b] describe initial investigations in the arid western United States.…”