A Standalone MEDA-TIRS Algorithm for Continuous Aerosol Optical Depth Retrieval on Jezero Crater, Mars

We present a standalone and fast algorithm for retrieving aerosol optical depth using data from the Mars Environmental Dynamics Analyzer Thermal-InfraRed Sensor (MEDA-TIRS) onboard NASA’s Mars 2020 Perseverance rover. MEDA-TIRS provides thermal infrared measurements during both daytime and nighttime, supplying a continuous and comprehensive dataset that captures variability across diurnal, seasonal and inter-annual timescales. This capability enables the retrieval of a nearly complete record of aerosol optical depth at the rover’s location since the beginning of the mission. Aerosol optical depth at the Perseverance site has previously been reported using onboard instruments, including MEDA, ZCAM and SCAM (Smith et al., 2024; Lemmon et al. 2025; Stcherbinine et al., this conference).
The algorithm operates independently of external datasets and is designed to be integrated directly into the MEDA data processing pipeline, allowing for systematic and autonomous retrievals. We describe the algorithm in detail and present results covering two full Martian years (MY 36 and MY 37) and the first half of MY 38. This temporal coverage allows for inter-annual and seasonal comparisons, the identification of local atmospheric events such as dust storms and the analysis of diurnal variability. The results also distinguish between two major periods: the aphelion season, dominated by water ice clouds, and the perihelion season, where dust is the dominant aerosol. In addition, the algorithm provides opacity data in near real time, enabling the early detection of dust events, which is of vital importance for the human exploration of Mars.