Broadband Measurements of the Complex Permittivity of Carbonaceous Asteroid Regolith Analog Materials

Abstract

We develop a full methodology to measure the complex relative permittivity of planetary regolith analog materials in vacuum and up to 120 °C over a broad range of frequencies (400 MHz to 8.5 GHz or wavelengths 18.8–3.5 cm). We demonstrate our method with measurements of analog regolith materials appropriate for asteroid (101955) Bennu, the target of National Aeronautics and Space Administration's OSIRIS‐REx mission: individual and mixed components of UCF/DSI‐CI‐2, a new carbonaceous asteroid regolith simulant produced by Deep Space Industries based on CI chondrite meteorite mineralogy. We measure, for the first time, the effect of carbonaceous material on the complex relative permittivity of asteroid regolith analogs by measuring the powdered serpentine component of the simulant mixed with varying amounts of carbonaceous material in vacuum at 25 and 40 °C. We find that at a bulk density of 1.60 g/cm3 and wavelength of 12.6 cm, serpentine with 5 wt% carbonaceous material has εr′ = 3.30 ± 0.01 and tanδ = 0.016 ± 0.003 and that carbonaceous material increases the attenuation of electromagnetic energy in our samples. Ground‐based radar (at 12.6‐ and 3.5‐cm wavelengths) has previously been used to investigate carbonaceous asteroid (101955) Bennu. Our measurements provide new constraints on the attenuation of radar energy in granular carbonaceous materials.

Simulated asteroid materials based on carbonaceous chondrite mineralogies

“…The asteroid simulants have already been delivered to researchers worldwide, and there are a variety of applications for these materials in basic science advances as well as technology maturation (e.g., Boivin et al. ; Fries et al. ).…”

Modeling the Dielectric Properties of Minerals From Crystals to Bulk Powders for Improved Interpretation of Asteroid Radar Observations

“…The samples were under vacuum for a minimum of 30 min prior to measurement to remove any moisture that had accumulated during the sample preparation process, although in most cases the samples were left in vacuum for 1–2 hr. The differences between permittivity measurements made on a given subsample after 30 min and 2 hr under vacuum are less than the reported uncertainty in each measurement, and so these vacuum conditions are considered comparable (see Figure 4 of Boivin et al., 2018). Silica aerogel was incrementally added to each subsample in order to artificially increase the proportion of void space in the subsample between repeated permittivity measurements, as described in Hickson et al.…”

“…For a detailed description of the measurement process and error estimation, the reader is referred to Boivin et al. (2018). The complex permittivity is calculated from the measured S parameters using the method described in Boughriet et al.…”

“…(2018). For a given permittivity measurement, the bulk density, ρ bd , of the subsample filled in a coaxial airline was calculated from the volume of the coaxial airline and the masses of the empty and filled airline (see Boivin et al., 2018 for details on the filling process). The volumes of each coaxial airline were measured using a digital caliper with ±0.001 cm accurary and a hole gauge micrometer with ±0.00025 cm accuracy, and the masses of the empty and filled airline were measured using the same Sartorius precision balance as described above.…”

Electrical properties of cometary dust particles derived from line shapes of TOF-SIMS spectra measured by the ROSETTA/COSIMA instrument

“…Rust et al 1999) and it is also used when probing the surface and subsurface areas of airless bodies in the planetary system, mostly by remote radar techniques (e.g. Campbell and Ulrichs 1969, Boivin et al 2018, Hickson et al 2018.…”