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

Abstract

[1] Radar detection of subsurface ice on Mars has been widely debated in part because the dielectric signature of ice, as deduced from the dielectric constant, can be confused with dry-silicate-rich materials. To identify the ice dielectric signature, it is crucial to estimate the imaginary part of the dielectric permittivity inferred from the dielectric attenuation after removing the scattering loss. Unfortunately, the latter remains poorly quantified at both Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) and shallow subsurface radar SHARAD frequencies. To address this ambiguity, we conducted multiple-frequency ground-penetrating radar and resistivity investigations in well-characterized temperate permafrost in Fairbanks, Alaska. The area shows several geomorphologic similarities to midlatitude and high-latitude terrains on Mars. This approach allowed us to quantify the dielectric and scattering losses in temperate permafrost over the 10 to 1000 MHz frequency band. At 20 MHz, our results suggest an average dielectric loss rate of 0.25 ± 0.03 dB/m, whereas the corresponding average scattering loss rate is 0.94 ± 0.37 dB/m. The scattering loss was found to represent ∼69% of the total signal attenuation. Considering this result and the study by Heggy et al. (2006a) in volcanic environments, we revised the interpretation of the attenuation coefficient calculated from SHARAD data over the Deuteronilus Mensae region and Amazonis Planitia; we then used the reevaluated dielectric loss to estimate the imaginary part of the dielectric permittivity. Our results suggest that even if Deuteronilus Mensae deposits and the Vastitas Borealis Formation may have similar dielectric constants, their imaginary parts are different. This implies that the two regions have different bulk compositions, with the former being ice-rich sediments and the latter being nonconsolidated volcanic deposits.

Radar probing of Jovian icy moons: Understanding subsurface water and structure detectability in the JUICE and Europa missions

“…The dielectric loss ranges are reported by Chyba et al (1998), Moore (2000), and Blankenship et al (2009); the surface scattering loss ranges are reported by Berquin et al (2013); and finally the volume scattering loss ranges are reported by Heggy et al (2006), Grimm et al (2006), and Boisson et al (2011).…”

Analysis of fluvial, lacustrine and anthropogenic landforms by means of ground‐penetrating radar (GPR): field experiment

“…Boisson et al . () stated that heterogeneities inside silt deposits produced energy losses of a GPR signal. In this way, the signal of the antennae they used (270, 400 and 900MHz) was shifted down.…”

“…Similar to the findings of Boisson et al . (), the cohesive deposits may have acted here as a low‐pass filter which influenced the resolution and depth of penetration.…”

Radar investigations of Apollinaris Mons on Mars: Exploring the origin of the fan deposits

“…However, the dielectric investigation of the martian subsurface using low frequency sounding data is associated with some ambiguities in interpreting the significance of the inverted dielectric values as different materials can have similar dielectric properties. For example, the ice dielectric signature inferred from the dielectric constant's real part cannot be distinguished from the one of lowloss silicate materials such as volcanic ashes or loose, dry sediments (Boisson et al, 2011). Moreover, the analysis of martian radargrams is subject to ambiguities in uniquely identifying subsurface reflectors due to surface clutter.…”

“…It should be noted that MARSIS has achieved a 2.5 km-deep subsurface penetration in the vicinity of Apollinaris Mons detecting the basal unit under the potentially unconsolidated pyroclastic deposits in the Medusa Fossae Formation (e.g., Watters et al, 2007;Kerber et al, 2012). Hence, the non-penetration in Apollinaris FD is an indication of higher subsurface dielectric losses in the structure consistent with volcanically derived materials (Boisson et al, 2011).…”