The dielectric permittivity of terrestrial ground ice formations: Considerations for planetary exploration using ground‐penetrating radar

Abstract

[1] Exploration of the polar ice caps and apparent glacial and periglacial landforms on Mars will aid our understanding of its ancient climate conditions and the history of water on the planet. Given that ground-penetrating radar (GPR) is likely to be used to understand these features, we investigated the real component of the complex dielectric permittivity of stratified segregation ice, non-stratified segregation ice, and polygonal ice wedge deposits in the Canadian Arctic. We acquired moveout profiles with a 450 MHz GPR on ground ice formations that had active layer sediments excavated prior to surveying. Using ice core data collected from these sites, we found that the volumetric fraction of ice plays the greatest role in defining the dielectric permittivity of the deposit and that it can be described using a modified complex refractive index method (CRIM) dielectric mixing model. Using the modified CRIM model, we estimate the dielectric permittivity of several ground ice deposits on Earth and present further estimates for similar features on Mars using permittivity values for Martian sediments derived from both theory and laboratory methods.

Internal Structure and Composition of a Rock Glacier in the Dry Andes, Inferred from Ground‐penetrating Radar Data and its Artefacts

“…If we consider that the elements in the rock glacier structure are randomly arranged, the Complex Refractive Index Model (CRIM) (Birchak et al ., ; Bittelli et al ., ) can be used to express the bulk dielectric permittivity over the studied points in terms of its constituent fractions: where ε i , ε r , ε w and ε a are the permittivities of ice, rock debris, water and air, respectively. The following values are used: 1 for air (Annan, ), 3.18 for ice (Johari and Charette, ), 88 for water close to the melting point (Thomson et al ., ) and 4 for rock debris (Campbell and Ulrichs, ). The volumetric fraction ( θ ) of the constituents previously estimated at each EM velocity point (Figure ) is used in Equation .…”

“…where ε i , ε r , ε w and ε a are the permittivities of ice, rock debris, water and air, respectively. The following values are used: 1 for air (Annan, 2003), 3.18 for ice (Johari and Charette, 1975), 88 for water close to the melting point (Thomson et al, 2012) and 4 for rock debris (Campbell and Ulrichs, 1969). The volumetric fraction (θ) of the constituents previously estimated at each EM velocity point (Figure 7) is used in Equation 6.…”

Internal structure and composition of a rock glacier in the Andes (upper Choapa valley, Chile) using borehole information and ground-penetrating radar

“…For understanding the velocity variations in the studied rock glacier, the components with the lowest (air = 1) and the highest permittivity (water = 88 when the temperature is close to the melting point; Thomson and others, 2012) are of special interest; ice and andesitic debris have permittivities of 3.2 and 3.5-5.0 (Campbell and Ulrichs, 1969; Abid, 2005), respectively. According to the rare measurements performed in samples retrieved from rock glacier boreholes (Arenson, 2002; Arenson and Springman, 2005), the air content must be low, <10-15%.…”

Ground penetrating radar geologic field studies of the ejecta of Barringer Meteorite Crater, Arizona, as a planetary analog

“…[19] Our study is concerned with GPR-based geologic interpretations, differing from field studies focusing on specific terrestrial conditions that most fully replicate a particular planetary dielectric environment or aim to determine geophysical parameters of analog subsurface materials [e.g., Paillou et al, 2001;Thomson et al, 2012;Heggy et al, 2006aHeggy et al, , 2006b. Planetary dielectrics can be estimated based on knowledge of earth materials but are hard to predict for specific local planetary sites.…”