Surface Energy Budget, Albedo and Thermal Inertia at Jezero Crater,
Mars, as Observed from the Mars 2020 MEDA Instrument
Abstract
The Mars Environmental Dynamics Analyzer (MEDA) on board Perseverance
includes first-of-their-kind sensors measuring the incident and
reflected solar flux, the downwelling atmospheric IR flux, and the
upwelling IR flux emitted by the surface. We use these measurements for
the first 350 sols of the Mars 2020 mission (Ls ~ 6-174
deg; in Martian Year 36) to determine the surface radiative budget on
Mars, and to calculate the broadband albedo (0.3-3 μm) as a function of
the illumination and viewing geometry. Together with MEDA measurements
of ground temperature, we calculate the thermal inertia for homogeneous
terrains without the need for numerical models. We found that: (1) the
observed downwelling atmospheric IR flux is significantly lower than
model predictions. This is likely caused by the strong diurnal variation
in aerosol opacity measured by MEDA, which is not accounted for by
numerical models. (2) The albedo presents a marked non-Lambertian
behavior, with lowest values near noon and highest values corresponding
to low phase angles (i.e., Sun behind the observer). (3) Thermal inertia
values ranged between 180 (sand dune) and 605 (bedrock-dominated
material) SI units. (4) Averages across Perseverance’ traverse of albedo
and thermal inertia (spatial resolution of ~3-4 m2) are
in very good agreement with collocated retrievals of thermal inertia
from THEMIS (spatial resolution of 100 m per pixel) and of bolometric
albedo in the 0.25-2.9 μm range from (spatial resolution of
~300 km2). The results presented here are important to
validate model predictions and provide ground-truth to orbital
measurements.