Cyclic absorption of solar radiation generates oscillations in atmospheric fields. These oscillations are called atmospheric or thermal tides, which are furthermore modified by topography and surface properties. This leads to a complex mix of sun-synchronous and non sun-synchronous tides that propagate around the planet eastward and westward. This study focuses on analyzing the ter-diurnal component (period of 8 hr) from surface pressure observations by Mars Science Laboratory (MSL), InSight, Viking Lander (VL) 1, and VL2. General Circulation Model (GCM) results are used to provide a global context for interpreting the observed ter-diurnal tide properties. MSL and InSight have a clear and similar seasonal cycle, with local amplitude peaks at around solar longitude (Ls) 60◦ , Ls 130◦ and Ls 320◦ . The amplitude peak at Ls 320◦ is related to the annual dust storm, while the dust storm around Ls 230◦ is not detected by either platforms. During the global dust storms, MSL, VL1, and VL2 detect their highest amplitudes. GCM predicts the weakest amplitudes at the equinoxes, while the strongest ones are predicted in summertime for both hemispheres. GCM amplitudes are typically lower than observed, but match better during the aphelion season. During this time, model results suggest that the two most prominent modes are the sun-synchronous ter-diurnal tide (TW3) and an eastward propagating resonantly-enhanced Kelvin wave (TE3). Simulations with and without the effect of radiative heating by water ice clouds indicate the clouds may play a significant role in forcing the ter-diurnal tide during northern hemisphere summer season.

The Mars2020 Perseverance Rover landed successfully on the Martian surface on the Jezero Crater floor (18.44°N, 77.45°E) at Martian solar longitude, $L_s$, $\sim$5 in February 2021. Since then it has produced highly valuable environmental measurements with a versatile scientific payload including the MEDA (Mars Environmental Dynamics Analyzer) suite of environmental sensors. One of the MEDA systems is the PS pressure sensor system which weighs 40 grams and has an estimated absolute accuracy of better than 3.5 Pa and a resolution of 0.13 Pa. We present initial results from the first 414 sols of Martian atmospheric surface pressure observations by the PS whose performance was found to meet its specifications. Observed sol-averaged atmospheric pressures follow an anticipated pattern of pressure variation in the course of the advancing season and are consistent with data from other landing missions. The observed diurnal pressure amplitude varies by $\sim$2-5 \% of the sol-averaged pressure, with absolute amplitude 10-35 Pa in an approximately direct relationship with airborne dust. During a regional dust storm, which began at $L_s~135^\circ$ the diurnal pressure amplitude roughly doubles. The diurnal pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular analysis of the diurnal pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations to data from other landers reveals the global scale seasonal behaviour of Mars’ atmosphere.

A document by Joonas Leino. Click on the document to view its contents.