RIMFAX Ground Penetrating Radar Reveals Dielectric Permittivity and Rock Density of Shallow Martian Subsurface

Abstract

The Mars Rover Perseverance is the first NASA Rover with a ground penetrating radar (GPR) payload, the "Radar Imager for Mars' Subsurface Experiment" (RIMFAX) (Hamran et al., 2020). RIMFAX has continuously sounded the upper tens of meters of the Martian subsurface along the Rover traverse, taking the first in situ observations of the shallow Martian subsurface with its long microwave penetration. In this study, we analyze the first 8 km of data, starting at the Octavia E. Butler landing site, where Perseverance landed on 18 February 2021 (see Figure 1 for a map of the landing site and Rover traverse).Numerous studies with Perseverance instruments have classified the overall surficial geology and mineralogy as igneous (e.g., Farley et al., 2022;Liu et al., 2022;Wiens et al., 2022). The study area is then characterized by the two major formations, Máaz Fm and Séítah Fm. For Máaz Fm, Udry et al. (2022) propose the material to be deposited by different lava flows or less likely pyroclastic flows. Its composition is basaltic to basaltic-andesitic. Spectral variability and morphology of Máaz-outcrops lead to further distinction of the Máaz-subregions, upper and lower Máaz, encompassing the eastern, respectively, southern part, with a transitional zone around the south-eastern tip of Séítah (Horgan et al., 2022). In contrast to Máaz, Séítah is interpreted as an olivine cumulate formed by slow cooling magma (Liu et al., 2022;Wiens et al., 2022). On average, Wiens et al. (2022) found less olivine and lower density in Máaz than Séítah. For the emplacement scenario they proposed either olivine settling in a common cumulate spanning Séítah and Máaz or separate lava flows for Máaz with respective erosional contrasts below. Based on radar reflections, Hamran et al. (2022) show that Séítah is the lowermost stratigraphic unit in the studied area, with Séítah horizons dipping under Máaz in multiple locations in the vicinity of the visible surface boundary between the two formations.

Radar Attenuation in the Shallow Martian Subsurface: RIMFAX Time‐Frequency Analysis and Constant‐Q Characterization Over Jezero Crater Floor

“…That attenuation is similar over the Jezero Crater Floor, is in line with results from Hamran et al (2022) where maximum imaging depths are fairly constant. Casademont et al (2023) analyzed dielectric permittivity in the RIMFAX data and found only small differences between regions. Similar propagation velocities and similar attenuation estimates, could indicate that the shallow subsurface electrical properties are comparable over the whole investigated area.…”

“…Moreover, all regions have mean values close to the combined estimate in (a), which for all soundings over the Crater Floor is Q* = 70.4 ± 7.7. At the RIMFAX 675 MHz center frequency, that equates to an attenuation of −2.6 ± 0.3 dB/m assuming a subsurface velocity of 0.1 m/ns (Casademont et al., 2023). Uncertainties are listed in terms of standard deviations.…”

“…Casademont et al. (2023) analyzed dielectric permittivity in the RIMFAX data and found only small differences between regions. Similar propagation velocities and similar attenuation estimates, could indicate that the shallow subsurface electrical properties are comparable over the whole investigated area.…”

“…Beyond that recording time, RIMFAX shallow mode spectra can be dominated by noise. For the average subsurface radar wave velocity in Jezero Crater of 0.1 m/ns (Casademont et al., 2023), 100 ns corresponds to a depth of 5 m.…”

The Dielectric Properties of Martian Regolith at the Tianwen‐1 Landing Site

“…The Radar Imager for Mars' Subsurface Experiment (RIMFAX) (150–1,200 MHz) aboard the Perseverance rover (Hamran et al., 2020) surveyed the Jezero crater (Hamran et al., 2022). The average permittivity detected by the RIMFAX on Perseverance in the Jezero Crater is 9.0 ± 2.8, with a mean depth of 1.9 ± 1.1 m (Casademont et al., 2022). The observed slopes, thicknesses, and internal morphology of the inclined stratigraphic sections by RIMFAX can be interpreted either as a magmatic layering formed in a differentiated igneous body or as a sedimentary layering commonly formed in aqueous environments on Earth (Hamran et al., 2022).…”