Aeolis Research (United States)

Abstract We present the temporal evolution of the effect of dust accumulation on two surfaces of the Curiosity rover at Gale crater during almost 4,000 sols using Rover Environmental Monitoring Station (REMS), Chemcam and Mastcam observations, and compare it with simulations of the Mars Weather Research and Forecasting Model (MarsWRF) atmospheric numerical model and environmental observations to improve our understanding of dust lifting on Mars. After almost six full Mars Years (MY), dust accumulated on the REMS UV sensor (UVS) attenuates an average of 45% of the incoming radiation. Dust accumulation on the UVS follows a seasonal cycle with gradual dust accumulation during the aphelion season followed by dust removal until Ls ∼ 300°. However, there is a strong interannual variability during the dusty season. MarsWRF simulations show that wind stress has a strong diurnal, seasonal and interannual variability; simulations of dust devil activity show a seasonal pattern that aligns with pressure drop observations, peaking also at Ls ∼ 300°. Dust lifting mechanisms are variable, with a larger relative importance of wind stress in MY 31 and 32, and of dust devils in MY 34 to 36. Dust accumulation on the Chemcam calibration target follows a very similar temporal evolution, but with a marked offset since the 2018 Global Dust Storm, suggesting that surface tilt is particularly important around intense dust storms. We characterize dust lifting mechanisms at Gale crater and quantify the effect of dust accumulation during an extraordinary dust storm on different surfaces; the observed net removal periods validate MarsWRF simulations and suggest the suitability of Gale Crater for long‐term solar‐powered missions.

Abstract The Perseverance rover has sampled mm‐size lithic fragments containing olivine likely from at least two source regions from the surface of an inactive megaripple surface, and fine‐grained material from the surface and to a depth of ∼4–6 cm. Some of the mm‐size grains lack a coherent diffraction pattern measured by PIXL, consistent with the presence of poorly ordered secondary phases that have been altered. Analysis of these materials on Earth will allow examination of materials that have experienced aqueous, potentially habitable environments that could contain biosignatures. Fluorescence of three different patterns was detected, consistent with inorganic emissions from silica defects or rare earth elements in certain mineral phases, although organic origin cannot be excluded. Analysis of Autofocus Context Imager and Wide Angle Topographic Sensor for Operations and eNgineering images of the subsurface material and MEDA thermal inertia measurements indicate average grain sizes of ∼125 and ∼150 μm, respectively, for the bulk material within the megaripple. The fine‐grained material in the sampling location indicates chemical compositions similar to previously proposed global components as well as airfall dust. In situ and associated atmospheric measurements provide evidence of recent processes likely including water vapor in soil crust formation. The sampled material will therefore help elucidate the formation of Martian soils; current surface‐atmosphere interactions; the composition, shape, and size distribution of dust grains valuable for studies of past and present Martian climate and for assessing potential health and other risks to human missions; and ancient, aqueously altered environments that could have been habitable, and, if Mars contained life, possibly contain biosignatures.

Abstract The Tropical Cloud Oscillation (TCO) in the Martian atmosphere is a shift of clouds in the northern spring and summer tropical cloud belt between the eastern and western hemispheres on an intra‐seasonal timescale of about 10–40 sols. The TCO is a significant intraseasonal variation and may strongly affect the Martian general circulation, water cycle, and dust cycle. We examine TCOs using multiple data sets with a focus on the clouds observed in Mars Daily Global Maps during Mars Year (MY) 29–35. One or more TCO cycles are observed in each MY and the phenomenon is most prominent during Ls = 135°–185°. Space‐time spectral analysis shows a variety of waves which appear to follow the theoretical dispersion relationships of equatorial waves, such as Kelvin waves, Rossby waves, and Mixed Rossby Gravity waves. The TCO appears to be controlled by zonal wavenumber one traveling waves with Kelvin and Rossby wave characteristics and exhibits a fine‐scale latitudinal structure that requires modeling with sufficient resolution. Issues with current data assimilation products for use in studies of Martian equatorial waves due to this fine‐scale structure are discussed.

Clouds play a crucial role in the past and current climate of Mars. Cloud particles impact the planet's energy balance and atmospheric dynamics, as well as influence the vertical distribution of dust particles through dust scavenging. This process of dust scavenging by clouds has significant consequences for the planet's water cycle. For example, regions in the atmosphere with insufficient quantities of dust particles, or condensation nuclei, can inhibit the formation of H2O clouds, leading to the presence of water vapor in excess of saturation [1]. Recent observations made by the MEDA Radiation and Dust Sensor (RDS) [2,3] have shown a marked decline in mesospheric cloud activity (above 35-40 km) when Mars is near its aphelion (within the Aphelion Cloud Belt-ACB season), notably occurring during solar longitudes (Ls) between Ls 70° and 80° [4] (see Figure 1).In order to investigate the possible factors leading to this decrease in water ice abundance, we used a one-dimensional cloud microphysical model [5,6], which includes the processes of nucleation, condensation, coagulation, evaporation, precipitation, and coalescence, and where the vertical mixing is parameterized using an eddy diffusion profile (Keddy). Combining cloud microphysics modeling with ground-based (Mars 2020 and InSight) and orbital observations (TGO and MRO) of clouds, water vapor, and temperature, we will discuss in this presentation the main factors controlling the water abundance in the Martian mesosphere during the ACB season.

The Mars Sample Return mission intends to retrieve a sealed collection of rocks, regolith, and atmosphere sampled from Jezero Crater, Mars, by the NASA Perseverance rover mission. For all life-related research, it is necessary to evaluate water availability in the samples and on Mars. Within the first Martian year, Perseverance has acquired an estimated total mass of 355 g of rocks and regolith, and 38 μmoles of Martian atmospheric gas. Using in-situ observations acquired by the Perseverance rover, we show that the present-day environmental conditions at Jezero allow for the hydration of sulfates, chlorides, and perchlorates and the occasional formation of frost as well as a diurnal atmospheric-surface water exchange of 0.5–10 g water per m2 (assuming a well-mixed atmosphere). At night, when the temperature drops below 190 K, the surface water activity can exceed 0.5, the lowest limit for cell reproduction. During the day, when the temperature is above the cell replication limit of 245 K, water activity is less than 0.02. The environmental conditions at the surface of Jezero Crater, where these samples were acquired, are incompatible with the cell replication limits currently known on Earth.

We investigate the vortex and dust devil activity on Jezero crater over more than one and half Martian years of meteorological data acquired by the MEDA sensors on the Mars 2020 Perseverance rover. During the initial phase of the M2020 mission (sols 15-415, Ls=152º-156º, Martian Year 36, MY36) Perseverance observed a strong vortex activity with a high frequency of dust devils (Newman et al. Science Advances, 2022; Hueso et al. JGR: Planets, 2023). However, later activity over Martian Autumn-Winter (MY36) showed a strong decrease in the frequency and intensity of vortices and dust devils that continued in Spring MY37 when Perseverance was close to the crater rim. Later data acquired over Summer MY37 shows a comparable level of activity than the previous Martian year. In this work, we explore how the combination of changes in the surface properties of the terrain, and the influence of the topography over more than 24 km of terrain traversed, are needed to explain the different levels of activity observed in similar seasons. The lack of accurate wind data after sol 315, when the wind sensors started to operate with some limitations (Viudez-Moreiras et al., 2022), does not allow us at present to model accurately vortex sizes and their distance from MEDA after that sol. We explore how the combined measurements from the pressure sensor (PS), the Atmospheric Temperature Sensors (ATS), and the Remote Dust Sensors (RDS) constraining the geometry of encounters with Dust Devils, give us information about the thermodynamics of the vortices. This analysis is done for a small selection of vortices where the combination of PS-ATS and RDS data shows a consistent geometry of the vortex encounter that validates the temperature enhancements observed during the vortex encounters.

In past global dust storms, no long lasting anomalies in the pressure cycle had been observed. The Global Dust Storm of Mars Year 34 (MY34), however, left behind an average surface pressure lower than what was expected based on the the values recorded on previous years by the Rover Environmental Monitoring Station (REMS) on Curiosity. The main signal contribution to the daily average surface pressure is the CO2 cycle, which is controlled by the Polar ice sublimation and freezing cycles. We used REMS and Mars Climate Sounder (MCS) data to search for correlations between the REMS anomaly and anomalies in the circulation compared to MCS observations from previous years. The findings include an early start of the retreat season for the Northern Polar cap, followed by the longest period of growth for the Southern Polar (SP) cap ice expansion since Curiosity had landed and then, during the dust storm, the longest retreat season of the Southern Polar cap. We also find a larger Northern Polar Cap extension after the storm, suggestive of a larger deposition of CO2 ice. The changes in length of the SP growth and retreat seasons might be consequence of the response of the zonal mean circulation to the dust storm. Changes in the structure of the zonal mean circulation compared to previous years are found in MCS data and presented. The combination of these anomalies constraint what physical processes may have caused this response in surface pressure after the dust storm.

We use a spectral approach to analyze the pressure and wind data from the InSight mission and investigate the diurnal and seasonal trends. Our analyses show that the daytime pressure and wind spectra have slopes of approximately −1.7 and −1.3 and, therefore, do not follow the Kolmogorov scaling (as was also previously reported for a reduced data set in Banfield et al.). We find that the nighttime pressure spectral slope is close to −1 (as reported in Temel et al.), and that the wind speed spectral slope is close to −0.5, flatter than the theoretical slope expected for the shear-dominated regime. We observe strong nocturnal (likely shear-generated) turbulent behavior starting around L s = 150° (InSight sol 440) that shifts to progressively earlier local times before reaching the “5th season” (InSight sols 530–710) identified by Chatain et al.. The diurnal spectral slope analyses indicate an asymmetry in the diurnal behavior of the Martian boundary layer, with a slow growth and fast collapse mechanism. Finally, the low-frequency (5–30 mHz) pressure data exhibit large spectral slope oscillations. These occur particularly during the periods with a highly stable atmosphere and, therefore, may be linked to gravity wave activity.

Abstract The response of tidal, “weather,” and intra‐seasonal transient eddies in a global numerical model to dust imposed in different latitudinal bands and seasons has been examined in order to investigate the impact of regional scale dust storm episodes on large‐scale circulation and hence on further dust storm development. The eddy kinetic energy and surface friction speed for each eddy group were derived using wavelet analysis from multi‐year simulations and statistical comparisons were made among the experiments. Results show that different eddy categories respond differently to dust storm forcing, and that the responses are dependent upon both modeled storm location and season. These responses can be cast in terms of potential positive and negative feedbacks on large‐scale dust storm development and have implications for the cascade of dust storms through different scales and circulation components. The model results suggest positive feedback between northern high latitude dust forcing and weather transients in the same latitudes in Quartober (Ls = 185°–245°), which weakens or disappears in Sixtober (Ls = 295°–360°). The results also suggest positive feedback between dust heating in the tropics/subtropics and tidal eddies, which may enhance the southward transport of “flushing” storms. However, southern high latitude dust forcing suppresses northern weather transients in both pseudo‐season sextons, suggesting negative feedback which may terminate northern frontal/flushing dust storm sequences and hence weaken further development of a dust storm episode through this mechanism.

CSV files containing information on Mars Science Laboratory Navigation Camera observations of dust lifting events. Including dates, sequence identifiers, dust lifting detection statistics, locations of some dust lifting events, and their implied directions of motion.