Geographical, Seasonal and Diurnal Variations of Acoustic Attenuation, and Sound Speed in the Near‐Surface Martian Atmosphere

Abstract

This work introduces a comprehensive model of sound attenuation and speed on Mars, in light of the recent operation of several microphones on the surface of Mars. The proposed acoustic model calculates the sound speed and attenuation throughout the near‐surface Martian atmosphere based on first‐principles. We evaluate the effects of the seasonal and diurnal cycle of air temperature, pressure and CO2, as well as the concentration of airborne dust on the sound attenuation. The attenuation and speed of sound are most sensitive to the air temperature and, therefore, they vary with the diurnal temperature cycle and to a lesser degree with the seasonal changes in temperature. The speed of sound also varies with the seasonal variations of the concentration of CO2. The main outcome of this work is an acoustic model capable of computing the sound speed and attenuation for any location at the Martian surface at any time of year and any time of day.

Acoustic Propagation in the Near‐Surface Martian Atmosphere

“…All the causes are assumed to be independent of one another when evaluating their effect. Hence, the geometric spreading is computed by multiplying the sound amplitude by 1 r , the attenuation by multiplying the sound amplitude by exp( αr) where α is the attenuation coefficient (Gillier et al, 2024), the losses caused by the ground, the temperature profile, the wind speed profile and turbulence are computed by subtracting a PE simulation with the relevant phenomenon to a PE simulation without. The losses obtained by simulating all the causes simultaneously (the full simulation) is also displayed.…”

“…In Gillier et al (2024), we presented a method to derive α and c for a sound wave of a given frequency. As a reminder, the main findings of that study that are relevant to this work are:…”

“…On the contrary, if the wind direction is from the source toward the detector it will create a positive gradient of effective sound speed, thus causing downward refraction of the sound and The wind profile Large (from 11 to +7 dB at 100 m depending on direction) a Atmospheric Turbulence Medium (+5 dB at 150 m) a a In the configuration presented in this work: a 100 Hz sound source 3 m above the ground with a receiver at 1.5 m from the ground. b For a 100 Hz soundwaves, see Gillier et al (2024).…”

“…In Gillier et al (2024) we proposed a model to compute the acoustic attenuation and sound speed in the nearsurface Martian atmosphere at any time and place. However, a sound wave traveling near the surface is not only attenuated by the atmosphere but also reflected by the ground and possibly refracted along its path.…”

“…The main outcome of this work is an operational acoustic model capable of simulating the sound field created by any source, at any location on the Martian surface, at any time. Expanding on the result of previous work (Gillier et al, 2024, https://doi.org/10.1029/ 2023je008257), we use the parabolic equation method for sound propagation in order to obtain the overall sound field produced by a source, in a given atmospheric composition and state, and accounting for ground properties. The resulting model enables the study of acoustics on Mars, and has the potential also to be used to probe the properties of the Martian environment using acoustic measurements with known sources.…”