Acoustic Propagation in the Near‐Surface Martian Atmosphere

• Published in: Journal of geophysical research. Planets Vol. 129; no. 7
• Main Authors: Gillier, Martin, Petculescu, Andi, Stott, Alexander E., Murdoch, Naomi, Jacob, Xavier, Chide, Baptiste, Maurice, Sylvestre, Mimoun, David
• Format: Journal Article
• Language: English
• Published: 01.07.2024
• Subjects: atmospheric acoustics; Mars acoustics; parabolic equation; sound propagation
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1029/2024JE008469

This work introduces a comprehensive model of sound propagation on Mars, in light of the recent operation of several microphones on the Martian surface. 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. We investigate the effects of the Martian ground and the vertical profile of temperature and wind, on sound propagation. We find that the ground has a minor effect on sound propagation, and the wind profile strongly influences sound propagation as on Earth. However, the midday near surface temperature profiles on Mars are shown to cause refraction, which generates non‐negligible acoustic losses that are an order of magnitude stronger than typical refraction‐related acoustic losses on Earth. We show that the effect of the Martian atmospheric turbulence is to slightly reduce the acoustic losses due to refraction. Finally, we apply our model to show that refraction and atmospheric turbulence have a negligible effect on the propagation of sound from Ingenuity to the Perseverance rover. Plain Language Summary Sound provides new ways for exploring the Martian environment. Whether to examine the characteristics of sound sources on Mars or to infer atmospheric properties from the behavior of sound waves in the Martian atmosphere, an accurate model of sound propagation on Mars is needed. This model must account for the path traveled by the sound waves in the atmosphere as well as their interactions with the planet's surface. We propose a model that allows us to compute the sound that would be received by a microphone depending on its relative position to a source given a set of atmospheric conditions. We investigate the effects of the ground, the vertical gradient of temperature and the wind speed, as well as the effects of atmospheric turbulence. We find that, because of the strong temperature gradient at noon on Mars, sound is bent upwards creating a quieter zone close to the ground. This effect also occurs on Earth, but is much stronger on Mars. The main outcome of this work is a model that can simulate the sound field created by any source for any location at the Martian surface at any time of year and any time of day. Key Points We have developed a model to compute the sound field created by a specific sound source at any time and place near the Martian surface Model predictions show that the main parameters affecting sound propagation are the temperature and wind speed profiles Refraction and atmospheric turbulence have a small effect on acoustic waves at the altitude of the Ingenuity rotorcraft