Frequency and time domain permittivity measurements on solid CO₂ and solid CO₂–soil mixtures as Martian soil simulants

Abstract

[1] Permittivity and conductivity measurements were performed to assess the dielectric behavior of solid CO 2 (i.e., CO 2 ice, snow, and powder) and solid CO 2 /soil mixtures. For comparison, some dielectric measurements were also conducted on H 2 O ice, dry glass beads, glass beads saturated with water, drained glass beads, and frozen drained glass beads. The measurements were performed in the frequency domain (20 Hz to 1 MHz) using a capacitive cell (Parallel Plate Capacitor) and in the time domain using a transmission line (Time Domain Reflectometry). The data obtained with both techniques have shown that solid CO 2 has a permittivity value that ranges between 1.4 and 2.1 as a function of density, values that distinguish it from H 2 O ice. In contrast, H 2 O ice, dry glass beads, frozen (drained) glass beads, and dry volcanic sand all have very similar permittivity values, and thus they cannot be clearly distinguished at higher frequencies. Data have also shown that a high volume fraction of solid CO 2 significantly reduces the permittivity value of a soil. Furthermore, almost all the samples tested in this work seem to behave like low loss materials, having a conductivity which is generally equal to or lower than 10 À6 Sm À1 at the highest frequency (and smaller values at lower frequencies). Finally, TDR measurements and data from some dielectric models were compared in order to assess the capability of these models to predict the permittivity of a granular multiphase material.

Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

“…The low values of the real part of permittivity measured for CO 2 powder (and CO 2 snow) were confirmed by TDR measurements, as shown in Table . This table compares the values found by Pettinelli et al [] with those reported in Simpson et al [], who measured samples of CO 2 powder as a function of density within the microwave frequency range of 2.2–12 GHz. Taking into account the difference in sample densities, the agreement between the two sets of measurements is significant, also in the case of the solid CO 2 ice sample, which was measured in Pettinelli et al [] and estimated using the Maxwell‐Garnett mixing formula in Simpson et al [].…”

Numerical simulation of a permittivity probe for measuring the electric properties of planetary regolith and application to the near‐surface region of asteroids and comets

“…The model background is described by σ = 10 −10 S/m and ε r = 4 and the layer by σ = 10 −6 S/m and ε r = 7, a setup typical for cold ice-dust mixtures with intervening water ice sheets. The chosen dielectric properties are consistent with those determined from laboratory experiments conducted at various temperatures and frequencies using mixtures of H 2 O and CO 2 ice with soil (Pettinelli et al 2003) and dry powders of dunite, montmorillonite, and kaolinite (Herique et al 2002). Such granular dust particles are considered as best available analog material for the refractory component of comets in terms of composition and grain size distribution.…”

“…The electrical conductivity of terrestrial rocks and sediments in the presence of moisture is about 10 mS/m (Grard 1990) and range from 10 −9 to 10 −10 S/m for dry lunar-type regolith at a frequency of 1 kHz (Carrier et al 1991). Thus, dielectric losses are negligible, even at the highest frequency, and the dielectric constant certainly dominates permittivity measurements in dry, porous regolith (Martinez and Byrnes 2001;Pettinelli et al 2003). …”

Shallow Radar (SHARAD), pedestal craters, and the lost Martian layers: Initial assessments

“…The constant value of 3.15 + i 6.3 × 10 −4 , as in the work by Picardi et al [2004], is a good representation for temperatures between 200 K and 230 K with respect to the models. Pettinelli et al [2003] experimentally obtained a range of 2.89 ≤ ɛ′ ice ≤ 3.29 and ɛ″ ice ∼ 6 × 10 −2 for 1 MHz and 250 K, depending on the method used. Here we adopt the same value as Picardi et al [2004], which is not only in agreement with the values discussed above, but also is consistent with the observations of a low‐loss, nearly pure ice northern polar layered deposits by both Picardi et al [2005] and Phillips et al [2008].…”