Mars 2020 MEDA ATS Measurements of Near Surface Atmospheric Temperatures at Jezero

The Mars Environmental Dynamics Analyzer (MEDA) is a meteorological station onboard Mars 2020 that characterizes the near surface atmosphere. Among other sensors MEDA has 5 Air Temperature Sensors (ATS) at two altitudes: 0.85m, in the front of the rover, and 1.45m around the Remote Sensing Mast, which are azimuthally distributed so that at least one sensor is located upwind. This configuration ensures that, for most environmental conditions, the thermal contamination caused by the rover can be set apart. Local air temperatures are read with a frequency of 1 or 2 Hz, and ATS data can characterize timescales from atmospheric turbulence to the daily temperature cycle and its seasonal evolution. 

Here we show the daily temperature cycle at Jezero and an analysis of its seasonal evolution over the first half Martian year of the mission from Spring (Ls=6) to Autumn Equinox (Ls=180). Simultaneous ATS and winds from MEDA’s wind sensors show that, for most rover orientations, solar irradiation and winds clean environmental measurements are obtained at the 1.45m level. However, clean measurements at the 0.85m level are not always fully achieved, and a small residual thermal contamination is found at this level in many measurement sessions. The daily temperature cycle reflects the daily cycle of convection and turbulence. Strong and fast thermal oscillations start a few hours after sunrise, peak near noon, and collapse before sunset. The seasonal evolution shows a progressive increase of temperatures as summer advances, but less steep than what is retrieved at other Martian locations by previous missions. At the 0.85m level, changes in atmospheric temperatures with time-scales of a few sols correlate well with variations in local terrain properties. At the 1.45m level, similar temperature changes with timescales of a few sols are also found. We investigate whether these changes at 1.45m can be associated with changing atmospheric opacity due to dust and clouds, which are measured by other MEDA sensors and additional instruments in Perseverance. From the two altitudes sampled with ATS, and additional data from the MEDA Thermal InfraRed Sensors (TIRS), which measure ground temperature and air temperature at 40m, we can obtain the near-surface vertical temperature profile for specific sols in which thermal contamination is moderate in all sensors. This allows us to study the evolution of the diurnal convective cycle and the vertical temperature gradient. In addition, the Supercam microphone can also deduce the average air temperature from the ground up to 2.1m high thanks to sound speed measurements during Supercam’s laser zapping rocks. Therefore, it gives an additional hint into the thermal gradient. Furthermore, the amplitude of the thermal oscillations characterizes the thermal turbulence and we present the spectra of turbulence for convective and non convective hours on different moments of the mission. Finally, we will show how the measured thermal data compares with model predictions of the daily cycle of temperatures, expected magnitude of thermal oscillations, and the seasonal evolution.