Characterization of Martian atmospheric turbulence using irradiance measurements from MEDA Radiation and Dust Sensor (RDS)

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Dust plays a fundamental role in shaping the dynamics of the Martian atmosphere. By interacting with solar radiation through scattering and absorption, it modifies atmospheric heating rates at the surface and aloft, driving buoyancy and vertical mixing processes. These thermally induced gradients contribute to the development and modulation of turbulent motions across different atmospheric layers. In turn, turbulence influences the lifting, transport, and redistribution of dust particles, leading to a tightly coupled, non-linear feedback system between radiative forcing and atmospheric dynamics.The Radiation and Dust Sensor (RDS) [1], part of the Mars Environmental Dynamics Analyzer (MEDA) [2] payload onboard the Mars 2020 Perseverance rover, is a radiometer that measures downwelling solar irradiance at the surface across multiple spectral bands at a frequency of 1Hz. Rapid temporal fluctuations in the measured irradiance are associated with variations in dust concentration induced by atmospheric turbulence.Most previous studies of Martian atmospheric turbulence have relied on near-surface in situ measurements (e.g. wind and temperature sensors) substantially limiting our understanding of Martian turbulence at higher altitudes. In contrast, the RDS radiometric signal, shaped by scattering along the zenith-pointing optical path, is sensitive to dust fluctuations at different altitudes, thereby enabling access to turbulent processes that are otherwise difficult to observe directly. Here, we study RDS irradiance fluctuations time series to characterize their spectral properties in the context of atmospheric turbulence; we analyze inertial-range behavior and introduce a synthetic turbulence modeling framework that, by treating dust as a passive and perfect tracer, allows us to directly examine how the RDS signal responds to atmospheric turbulence. In particular, this approach makes it possible to assess how variations in turbulent behavior across different layers, together with the structure of the vertical atmospheric profile, influence both the fluctuations of the RDS signal and the characteristics of its inertial range. References:[1] Apestigue, V., et al. “Radiation and Dust Sensor for Mars Environmental Dynamic AnalyzerOnboard M2020 Rover”. Sensor 22.8 (2022): 2907.[2] Rodriguez-Manfredi, Jose Antonio, et al. “The Mars Enviromental Dynamics Analyzer, MEDA. A suite of enviromental sensors for the Mars 2020 mission.” Space science reviews 217.3 (2021): 1-86.

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