Autocorrelation Infrasound Interferometry on Mars

A high-sensitivity pressure sensor was deployed as part of the Mars Interior Exploration using Seismic Investigations, Geodesy and Heat Transport lander on Elysium Planitia in November 2018. We use pressure records from 1 October to 31 December 2019 (Sol 301-389) for frequencies between 0.1 and 0.5 Hz to infer relative sound-speed changes in the Martian atmosphere using the autocorrelation infrasound interferometry method. We find that relative sound-speed changes are up to +/- 15%, follow a similar pattern to Martian-daily variations of atmospheric temperature and horizontal wind velocity, and are similar to those inferred from in-situ observations and Martian climatology. The relative sound-speed changes and horizontal wind speed variations are synchronous, while temperature peaks similar to 1.88 hr after these time series. The strong and continuous emergence of coherent phases in the autocorrelation codas suggests the presence of continuous infrasound on Mars.