Vertical and horizontal heterogeneity of atmospheric dust loading in northern Gale Crater, Mars

Fluidisation of Aeolian Sandstone in Gale crater: evidence for water post-dating exhumation of Mount Sharp

Baroclinic waves are large-scale atmospheric disturbances driven by meridional temperaturegradients. While they typically form in mid-latitudes, previous studies have shown their presenceeven at equatorial latitudes in the Martian atmosphere. These eastward-propagating waves haveperiods of 2-10 sols and are most prevalent during the fall, winter, and spring seasons, whentemperature gradients are strongest. Surface pressure measurements offer a valuable tool fordetecting these oscillations, as they produce distinctive pressure patterns that reflect the presence,propagation, and intensity of baroclinic waves.In this study, we analyze in-situ surface pressure data collected by Viking Lander 1 (VL1; 22.5°N),Viking Lander 2 (VL2; 48°N), the Mars Phoenix Lander (68.2°N), the Mars Science Laboratory(MSL) Curiosity rover (4.6°S), and the InSight lander (4.5°N). The periods and amplitudes ofpressure oscillations over multiple Martian years were determined using spectral analysis with aniterative mode removal method.VL2 observed significant wave activity with periods of 2-4 sols during the northern fall, winter, andspring. Amplitudes generally increased as the season progressed, with particularly high values (>30Pa) during northern spring of Mars Year (MY) 13, peaking at a period of 2.23 sols. In addition,wave activity was detected at longer periods between 5 and 12 sols.During MY 35, InSight detected wave activity with periods of 2-3 sols during the northern fall,winter, and spring, with the highest amplitudes during the winter season. The period graduallyincreased from 2.1 sols to 2.25 sols, and then to 2.35 sols. Additionally, a clear peak with a periodof approximately 6.5 sols was observed during northern winter. In late northern spring, waves withperiods around 3.8-4.3 sols dominated, while in early northern summer, waves with periods near 3.2sols were most prevalent. In late northern summer, waves with periods ranging from 3.9 to 4.6 solswere most common. Similar wave activity was observed by the MSL during MY 35, although MSLwaves show some year-to-year variation. These waves detected by MSL and InSight during thenorthern fall, winter, and spring exhibit periods similar to those observed by VL2 in mid-latitudes,though with lower amplitudes, and may be associated with northern hemisphere mid-latitudebaroclinic waves. In contrast, waves detected during the northern summer are likely associated withbaroclinic waves from the southern mid-latitudes.The wave activity observed at VL1 differs slightly from that observed at MSL and InSight. Waveswith periods of 2-3 sols exhibit higher amplitudes at VL1 during northern hemisphere fall throughspring. Additionally, waves with periods of 6-9 sols tend to have higher amplitudes at VL1compared to those at MSL and InSight. However, amplitudes are generally similar during the winterseason. The observed differences between these locations may be attributed to VL1’s higherlatitudinal position.Phoenix observed pressure only during the northern hemisphere summer season. Waves withperiods of 5-10 sols, 3.25-3.5 sols, 7.5-9 sols, and 5.2-5.7 sols were detected. These periods aresomewhat similar to those observed by VL2 during the same season.

Proceedings of the National Academy of Sciences (PNAS), a peer reviewed journal of the National Academy of Sciences (NAS) - an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.

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.

Characterization of a local dust storm on Mars with REMS/MSL measurements and MARCI/MRO images

Why do some Martian dust storms, in some Mars years, expand to reach planet-encircling status, while the majority do not? In what ways do the largest regional events differ from those that become global? Comparisons of observations from these two categories of events may help answer these questions. The dust storm season of 2018, which included a global-scale dust event, was preceded by five successive dust storm seasons in which only regional-scale events were observed. The recent record thus presents an opportunity for making quantitative comparisons between regional-scale and global-scale dust events. Observations by the Mars Climate Sounder, on board the Mars Reconnaissance Orbiter spacecraft, provide unique 4D information on temperatures and aerosol loading of the Mars atmosphere, to altitudes of >80 km. Available MCS observations span the past eight Mars years. We have previously employed MCS observations to characterize the evolution in latitude, longitude, and altitude of atmospheric dust clouds during the initiation phase of the 2018 global event. Other atmospheric fields provide complementary information. For instance, observed changes with time in atmospheric ‘dynamical heating’ also help characterize the response of the Mars atmosphere to added dust loading. In this process, the atmosphere in regions far removed from the locations where dust is lifted may be warmed by adiabatic compression within the descending branches of Hadley-like meridional circulation cells. We will present and interpret MCS observations of these and other phenomena for selected large regional-scale dust events of Mars Years 29-33 (from 2009 through 2017), and draw comparisons with observations obtained during the 2018 global event. We will additionally explore the implications of the results within the context of current hypotheses for the triggering of the largest dust storms on sub-seasonal time scales.

Persistent aeolian activity at Endeavour crater, Meridiani Planum, Mars; new observations from orbit and the surface

Moats in the residual south polar cap of Mars: Ages, formation, and evolution

During the period October 1997 to September 1999 we obtained and analyzed over 100 millimeter‐wave observations of Mars atmospheric CO line absorption for atmospheric temperature profiles. These measurements extend through one full Mars year (solar longitudes LS of 190° in 1997 to 180° in 1999) and coincide with atmospheric temperature profile and dust column measurements from the Thermal Emission Spectrometer (TES) experiment on board the Mars Global Surveyor (MGS) spacecraft. A comparison of Mars atmospheric temperatures retrieved by these distinct methods provides the first opportunity to place the long‐term (1982–1999) millimeter retrievals of Mars atmospheric temperatures within the context of contemporaneous, spatially mapped spacecraft observations. Profile comparisons of 0–30 km altitude atmospheric temperatures retrieved with the two techniques agree typically to within the 5 K calibration accuracy of the millimeter observations. At the 0.5 mbar pressure level (∼25 km altitude) the 30°N/30°S average for TES infrared temperatures and the disk‐averaged millimeter temperatures are also well correlated in their seasonal and dust‐storm‐related variations over the 1997–1999 period. This period includes the Noachis Terra regional dust storm, which led to very abrupt heating (∼15 K at 0.5 mbar) of the global Mars atmosphere at LS = 224° in 1997 [Christensen et al., 1998; Conrath et al., this issue; Smith et al., this issue]. Much colder (10–20 K) global atmospheric temperatures were observed during the 1997 versus 1977 perihelion periods (LS = 200°–330°), consistent with the much (2 to 8 times) lower global dust loading of the atmosphere during the 1997 perihelion dust storm season versus the Viking period of the 1977a,b storms. The 1998–1999 Mars atmosphere revealed by both the millimeter and TES observations is also 10–15 K colder than presented by the Viking climatology during the aphelion season (LS = 0°–180°, northern spring/summer) of Mars. We reassess the observational basis of the Viking dusty‐warm climatology for this season to conclude that the global aphelion atmosphere of Mars is colder, less dusty, and cloudier than indicated by the established Viking climatology even for the Viking period. We also conclude that Mars atmospheric temperatures exhibit their most significant interannual variations during the perihelion dust storm season (10–20 K for LS = 200°–340°) and during the post‐aphelion northern summer season (5–10 K for LS = 100°–200°).

The Mars Science Laboratory rover Curiosity scooped samples of soil from the Rocknest aeolian bedform in Gale crater. Analysis of the soil with the Chemistry and Mineralogy (CheMin) x-ray diffraction (XRD) instrument revealed plagioclase (~An57), forsteritic olivine (~Fo62), augite, and pigeonite, with minor K-feldspar, magnetite, quartz, anhydrite, hematite, and ilmenite. The minor phases are present at, or near, detection limits. The soil also contains 27 ± 14 weight percent x-ray amorphous material, likely containing multiple Fe(3+)- and volatile-bearing phases, including possibly a substance resembling hisingerite. The crystalline component is similar to the normative mineralogy of certain basaltic rocks from Gusev crater on Mars and of martian basaltic meteorites. The amorphous component is similar to that found on Earth in places such as soils on the Mauna Kea volcano, Hawaii.

Since 2012, the Mars Science Laboratory rover Curiosity has studied the sedimentary record of the Gale Crater. This work focuses on the sedimentary record of the Kimberley outcrop, traversed by Curiosity between sols 603 and 630. This section presents siliciclastic rocks with an unusually high potassic content (Le Deit et al., JGR-Planets, 2016). However, poorly constrained stratigraphic relations between the series of the Kimberley Formation and their local to regional surroundings prevent further understanding of the exact extent of these accumulations and their significance within the broader Gale Crater paleoenvironmental scheme. Such questions highlight the need for a new finer mapping of the area to notably characterize the precise nature and morphology of the sedimentary structures and contacts observed on the outcrop itself and in its immediate vicinity. We therefore propose to use a true color highly resolved (up to the mm-scale) Digital Outcrop Model (DOM) of the Kimberley outcrop, obtained using Mars Science Laboratory imagery, integrated into a Virtual Reality (VR) environment. Taking advantage of purposely-developed measurement tools dedicated to the VR exploration and “in situ” geological analysis of DOM, we were able to observe and characterize such sedimentary structures and contacts, as well as their spatial extension throughout the reconstructed area of Kimberley. This new edge technique allows us to observe and describe with unprecedented precision both conformable and unconformable contacts, and several set of varying scale cross-stratifications (from cm- to pluri-meter scale). These results tend to corroborate the idea of a complex and diachroneous evolution of the area, with the possibility of laterally evolving depositional settings, spanning a significant amount of time. Newly developed tools in Virtual Reality therefore give us the opportunity to study “in situ” digital reconstructions of Martian outcrops such as Kimberley and represent a major advance for the characterization and interpretation of remote planetary past paleoenvironments.

Variability of temperatures and gravity wave activity in the Martian thermosphere during low solar irradiance

In 2011 NASA will launch the Mars Science Laboratory (MSL) as part of its Mars Exploration Program to learn more about the red planet's environment and geological history. To fulfill that goal, the MSL rover, built by NASA's Jet Propulsion Laboratory (JPL), is outfitted with the most extensive array of scientific instruments ever landed on the Martian surface. The Mars Hand Lens Imager (MAHLI), mounted on the end of the rover's robotic arm, is one of the primary science cameras for MSL. This camera affords many improvements over those used on previous Mars missions, particularly the ability to focus throughout a wide spatial range. A novel mechanism uses one motor to actuate an internal lens group, enabling focus capability, and manipulate a protective dust cover. This mechanism is designed to operate in the severe thermal environment of the MSL mission (-120deg C to +40deg C) and to survive for one Martian year with 3x margin (about 2000 Earth days) using non-standard materials and techniques in order to meet mass and optical requirements. Several issues involving lubrication and wear were encountered in developing this instrument; each solved through sound engineering and/or system level redesign. The qualification model passed full level life testing at temperatures throughout the operating range with negligible reduction in performance. Alliance Spacesystems, LLC supplied the flight model mechanism to Malin Space Science Systems (MSSS) where it was integrated with electronics and in turn delivered to JPL in October 2008.

The Mars Science Laboratory (MSL) Curiosity rover is exploring the Murray formation, a sequence of heterolithic mudstones and sandstones recording fluvial deltaic and lake deposits that comprise over 350 m of sedimentary strata within Gale crater. We examine >4,500 Murray formation bedrock points, employing recent laboratory calibrations for ChemCam laser‐induced breakdown spectroscopy H measurements at millimeter scale. Bedrock in the Murray formation has an interquartile range of 2.3–3.1 wt.% H2O, similar to measurements using the Dynamic Albedo of Neutrons and Sample Analysis at Mars instruments. However, specific stratigraphic intervals include high H targets (6–18 wt.% H2O) correlated with Si, Mg, Ca, Mn, or Fe, indicating units with opal, hydrated Mg sulfates, hydrated Ca sulfates, Mn‐enriched units, and akageneite or other iron oxyhydroxides, respectively. One stratigraphic interval with higher hydrogen is the Sutton Island unit and Blunts Point unit contact, where higher hydrogen is associated with Fe‐rich, Ca‐rich, and Mg‐rich points. A second interval with higher hydrogen occurs in the Vera Rubin ridge portion of the Murray formation, where higher hydrogen is associated with Fe‐rich, Ca‐rich, and Si‐rich points. We also observe trends in the H signal with grain size, separate from chemical variation, whereby coarser‐grained rocks have higher hydrogen. Variability in the hydrogen content of rocks points to a history of water‐rock interaction at Gale crater that included changes in lake water chemistry during Murray formation deposition and multiple subsequent groundwater episodes.

The Curiosity rover on the Mars Science Laboratory mission has found extensive evidence that Gale crater once hosted a habitable lacustrine environment; however, there are remaining questions about the chemistry and duration of the lake and the nature of the climate at the time. In this study, we use Mastcam multispectral data to investigate the mineralogy of the Sutton Island member of the Murray formation, a part of the basal layers of Mt. Sharp, which consists of heterolithic mudstone and sandstone that are distinct from the finely laminated mudstones that dominate much of the Murray. Sutton Island includes at least one instance of desiccation cracks, indicative of subaerial exposure, and uniquely irregular diagenetic features that may be related to local bedrock permeability. These features suggest that Sutton Island experienced a complex history of deposition and diagenesis which may be crucial for understanding changing water‐rock interactions within Gale. We find that most Mastcam bedrock spectra in this region lack the absorptions associated with hematite found throughout the Murray, and instead show deeper absorptions shifted toward longer wavelengths that are more consistent with Fe‐smectites such as nontronite. Elemental chemistry from ChemCam supports this interpretation, as SiO, MgO, Li, and the chemical index of alteration are elevated in this region. Combined with observations of bedrock sedimentology, this suggests that Sutton Island was deposited in a nearshore or low stand environment, and we hypothesize that the clay minerals were produced in this region due to sub‐aerial exposure and weathering in a semi‐arid climate.