Mars Exploration Using Sailplanes

We present the preliminary design of sailplanes, used for Mars exploration. The sailplanes mitigate the weight and energy storage limitations traditionally associated with powered flight by instead exploiting atmospheric wind gradients for dynamic soaring, and slope/thermal updrafts for static soaring. Equations of motion for the sailplanes were combined with wind profiles from the Mars Regional Atmospheric Modeling System (MRAMS) for two representative sites: Jezero crater, Perseverance’s landing site, and over a section of the Valles Marineris canyon. Optimal flight trajectories were obtained from the constrained optimization problem, using the lift coefficient and the roll angle as control parameters. Numerical results for complete dynamic soaring cycles demonstrated that the total sailplane energy at the end of a soaring cycle increases by 6.8–11%. The absence of a propulsion system, allowing for a compact form factor, means the sailplanes can be packaged into CubeSats and deployed as secondary payloads at a relatively low cost; providing scientific data over locations inaccessible by current landers and rovers. Various sailplane deployment methods are considered, including rapid deployment during Entry, Descent, and Landing (EDL) of a Mars Science Laboratory-class (MSL) vehicle and slow deployment using a blimp.

Diurnal Variations of Water Ice in the Martian Atmosphere Observed by Mars Climate Sounder

Simulation studies have proposed a significant thermal effect of water ice clouds on the Martian atmosphere and climate. However, previous studies focused more on seasonal variations but less on short-term changes. In this work, we used the MCS multi-local time data to investigate the water ice diurnal variations on Mars. We quantified its diurnal variations with amplitude and phase by applying the tidal fitting method to the water ice abundance. In addition, we found a close correlation (antiphase relation) between the thermal tide and water ice diurnal variations during the aphelion seasons that was not sensitive to both the background water ice and dust opacity but increased with the tidal amplitude. In the perihelion seasons, the antiphase relation was sensitive to the water ice and dust opacity, both affected by the dust storm activity. Finally, the statistic results suggested an unexpected low threshold of diurnal tide amplitude (2 to 3 K) for generating a relevant water ice diurnal variation, accounting for the ubiquitous water ice diurnal variations in the Martian atmosphere. These new observational results can help further understand the phase transition process between ice and vapor in the Martian atmosphere and better constrain the Martian global climate model in the future.

Vertical Aerosol Distribution and Mesospheric Clouds From ExoMars UVIS

The vertical opacity structure of the martian atmosphere is important for understanding the distribution of ice (water and carbon dioxide) and dust. We present a new data set of extinction opacity profiles from the NOMAD/UVIS spectrometer aboard the ExoMars Trace Gas Orbiter, covering one and a half Mars Years (MY) including the MY 34 Global Dust Storm and several regional dust storms. We discuss specific mesospheric cloud features and compare with existing literature and a Mars Global Climate Model (MGCM) run with data assimilation. Mesospheric opacity features, interpreted to be water ice, were present during the global and regional dust events and correlate with an elevated hygropause in the MGCM, providing evidence that regional dust storms can boost transport of vapor to mesospheric altitudes (with potential implications for atmospheric escape). The season of the dust storms also had an apparent impact on the resulting lifetime of the cloud features, with events earlier in the dusty season correlating with longer-lasting mesospheric cloud layers. Mesospheric opacity features were also present during the dusty season even in the absence of regional dust storms, and interpreted to be water ice based on previous literature. The assimilated MGCM temperature structure agreed well with the UVIS opacities, but the MGCM opacity field struggled to reproduce mesospheric ice features, suggesting a need for further development of water ice parameterizations. The UVIS opacity data set offers opportunities for further research into the vertical aerosol structure of the martian atmosphere, and for validation of how this is represented in numerical models.

Assimilation of Both Column- and Layer-Integrated Dust Opacity Observations in the Martian Atmosphere

A new dust data assimilation scheme has been developed for the UK version of the Laboratoire de Météorologie Dynamique Martian General Circulation Model. The Analysis Correction scheme (adapted from the UK Met Office) is applied with active dust lifting and transport to analyze measurements of temperature, and both column-integrated dust optical depth (CIDO), τ _ref (rescaled to a reference level), and layer-integrated dust opacity (LIDO). The results are shown to converge to the assimilated observations, but assimilating either of the dust observation types separately does not produce the best analysis. The most effective dust assimilation is found to require both CIDO (from Mars Odyssey/THEMIS) and LIDO observations, especially for Mars Climate Sounder data that does not access levels close to the surface. The resulting full reanalysis improves the agreement with both in-sample assimilated CIDO and LIDO data and independent observations from outside the assimilated data set. It is thus able to capture previously elusive details of the dust vertical distribution, including elevated detached dust layers that have not been captured in previous reanalyzes. Verification of this reanalysis has been carried out under both clear and dusty atmospheric conditions during Mars Years 28 and 29, using both in-sample and out of sample observations from orbital remote sensing and contemporaneous surface measurements of dust opacity from the Spirit and Opportunity landers. The reanalysis was also compared with a recent version of the Mars Climate Database (MCD v5), demonstrating generally good agreement though with some systematic differences in both time mean fields and day-to-day variability.

The Mars Environmental Dynamics Analyzer, MEDA. A Suite of Environmental Sensors for the Mars 2020 Mission

NASA's Mars 2020 (M2020) rover mission includes a suite of sensors to monitor current environmental conditions near the surface of Mars and to constrain bulk aerosol properties from changes in atmospheric radiation at the surface. The Mars Environmental Dynamics Analyzer (MEDA) consists of a set of meteorological sensors including wind sensor, a barometer, a relative humidity sensor, a set of 5 thermocouples to measure atmospheric temperature at ∼1.5 m and ∼0.5 m above the surface, a set of thermopiles to characterize the thermal IR brightness temperatures of the surface and the lower atmosphere. MEDA adds a radiation and dust sensor to monitor the optical atmospheric properties that can be used to infer bulk aerosol physical properties such as particle size distribution, non-sphericity, and concentration. The MEDA package and its scientific purpose are described in this document as well as how it responded to the calibration tests and how it helps prepare for the human exploration of Mars. A comparison is also presented to previous environmental monitoring payloads landed on Mars on the Viking, Pathfinder, Phoenix, MSL, and InSight spacecraft.

Baroclinic waves in the northern hemisphere of Mars as observed by the MRO Mars Climate Sounder and the MGS Thermal Emission Spectrometer

The climatology of baroclinic waves in the northern hemisphere of Mars is investigated through analysis of observations by the infrared sounders on Mars Reconnaissance Orbiter (MRO) and Mars Global Surveyor (MGS). We focus on the lowest scale height above the surface, where the waves have a large impact on the Martian dust cycle. Profiles retrieved by the MRO Mars Climate Sounder (MCS) rarely reach the lower atmosphere at the season and location of interest. To fill this gap, we turn to observations in the MCS B1 channel (32 microns) when the instrument is viewing the surface. The signature of baroclinic waves appears in these data because of dust-related emission from the lower atmosphere and wave-induced variations of surface temperature. We supplement the MCS data with measurements of temperature at the 610-Pa pressure level from the MGS Thermal Emission Spectrometer (TES). Both data sets provide systematic coverage in latitude and longitude at two local times. Characteristics of baroclinic waves are derived through analysis of observations with a combined duration of about 8 Mars years. Basic results include least-squares solutions for wave amplitude and period at zonal wavenumber 1-3; the resolution is 4° in latitude and 14 solar days in time of observation. There is a strong similarity between the baroclinic waves observed by MCS and TES, which confirms the sensitivity of the MCS B1 channel to wave activity at pressures near 610 Pa. In all 8 Mars years, the baroclinic waves exhibit periodic transitions among modes with different zonal wavenumbers and a distinctive solstitial pause. Although the weather in each Mars year is unique in some respects, a composite of results from all years reveals a well-defined wave climatology. At each zonal wavenumber, large amplitudes are restricted to a pair of seasonal windows positioned symmetrically about the winter solstice. The wave-2 mode is strongest in early autumn and near the vernal equinox, whereas wave 3 is the dominant mode in mid-autumn and mid-winter, immediately before and after the solstitial pause. The interaction between baroclinic waves and dust storms is investigated through comparisons with spacecraft measurements of dust opacity. A strong wave-3 mode is often present during the initial growth phase of large, seasonal dust storms, which reflects the importance of wave-generated frontal dust storms in triggering these events. The wave-3 amplitude then decreases rapidly as the dust storm evolves; this occurs routinely in all Mars years considered here in connection with both mid-autumn "A" storms and mid-winter "C" storms. In some years A-storm suppression of the wave-3 mode marks the beginning of the solstitial pause. These results provide a basis for testing and development of Mars General Circulation Models as well as context for interpreting contemporaneous observations, such as spacecraft images of frontal and flushing dust storms.

Hydrogen escape from Mars is driven by seasonal and dust storm transport of water

Mars has lost most of its once-abundant water to space, leaving the planet cold and dry. In standard models, molecular hydrogen produced from water in the lower atmosphere diffuses into the upper atmosphere where it is dissociated, producing atomic hydrogen, which is lost. Using observations from the Neutral Gas and Ion Mass Spectrometer on the Mars Atmosphere and Volatile Evolution spacecraft, we demonstrate that water is instead transported directly to the upper atmosphere, then dissociated by ions to produce atomic hydrogen. The water abundance in the upper atmosphere varied seasonally, peaking in southern summer, and surged during dust storms, including the 2018 global dust storm. We calculate that this transport of water dominates the present-day loss of atomic hydrogen to space and influenced the evolution of Mars' climate.

Surface Warming During the 2018/Mars Year 34 Global Dust Storm

The impact of Mars's 2018 Global Dust Storm (GDS) on surface and near-surface air temperatures was investigated using an assimilation of Mars Climate Sounder observations. Rather than simply resulting in cooling everywhere from solar absorption (average surface radiative flux fell 26 W/m2), the globally averaged result was a 0.9-K surface warming. These diurnally averaged surface temperature changes had a novel, highly nonuniform spatial structure, with up to 16-K cooling/19-K warming. Net warming occurred in low thermal inertia regions, where rapid nighttime radiative cooling was compensated by increased longwave emission and scattering. This caused strong nightside warming, outweighing dayside cooling. The reduced surface-air temperature gradient closely coupled surface and air temperatures, even causing local dayside air warming. Results show good agreement with Mars Climate Sounder surface temperature retrievals. Comparisons with the 2001 GDS and free-running simulations show that GDS spatial structure is crucial in determining global surface temperature effects.

A Multiannual Record of Gravity Wave Activity in Mars's Lower Atmosphere from On-Planet Observations by the Mars Climate Sounder

Gravity waves in Mars's atmosphere strongly affect the general circulation as well as middle atmospheric cloud formation, but the climatology and sources of gravity waves in the lower atmosphere remain poorly understood. At Earth, the statistical variance in satellite observations of thermal emission above the instrumental noise floor has been used to enable measurement of gravity wave activity at a global scale. Here is presented an analysis of variance in calibrated radiance at 15.4 μm (635-665 cm-1) from off-nadir and nadir observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter (MRO); a major expansion in the observational data available for validating models of Martian gravity wave activity. These observations are sensitive to gravity waves at 20-30 km altitude with wavelength properties (λ h =10-100 km, λ z > 5 km) that make them likely to affect the dynamics of the middle and upper atmosphere. We find that: (1) strong, moderately intermittent gravity wave activity is scattered over the tropical volcanoes and throughout the middle to high latitudes of both hemispheres during fall and winter, (2) gravity wave activity noticeably departs from climatology during regional and global dust storms; and (3) strong, intermittent variance is observed at night in parts of the southern tropics during its fall/winter, but frequent CO2 ice clouds prevents unambiguous attribution to GW activity. The spatial distribution of wave activity is consistent with topographic sources being dominant, but contributions from boundary layer convection and other convective processes are possible.

Dust tides and rapid meridional motions in the Martian atmosphere during major dust storms

The atmosphere of Mars is strongly affected by the spatial and temporal variability of airborne dust. However, global dust variability within a sol (Martian day) is still poorly understood. Although short-term dynamic processes are crucial, detailed comparisons of simulated diurnal variations are limited by relatively sparse observations. Here, we report the discovery of ubiquitous, strong diurnal tides of dust in the Southern Hemisphere of Mars. Driven by the westward-propagating migrating diurnal thermal tide, zonally distributed dust fronts slosh back and forth in a wide latitudinal range of up to 40° within one sol during major dust storms. Dust tides-tidal transport of dust in this way-rapidly transport heat and constituents meridionally, allowing moist air near the summer pole to be rapidly transported to lower latitudes during the night, where it then can be lifted by daytime deep convection and contribute to hydrogen escape from Mars during global dust storms.

Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season

The loss of water from Mars to space is thought to result from the transport of water to the upper atmosphere, where it is dissociated to hydrogen and escapes the planet. Recent observations have suggested large, rapid seasonal intrusions of water into the upper atmosphere, boosting the hydrogen abundance. We use the Atmospheric Chemistry Suite on the ExoMars Trace Gas Orbiter to characterize the water distribution by altitude. Water profiles during the 2018-2019 southern spring and summer stormy seasons show that high-altitude water is preferentially supplied close to perihelion, and supersaturation occurs even when clouds are present. This implies that the potential for water to escape from Mars is higher than previously thought.

An Observational Overview of Dusty Deep Convection in Martian Dust Storms

Deep convection, as used in meteorology, refers to the rapid ascent of air parcels in the Earth's troposphere driven by the buoyancy generated by phase change in water. Deep convection undergirds some of the Earth's most important and violent weather phenomena and is responsible for many aspects of the observed distribution of energy, momentum, and constituents (particularly water) in the Earth's atmosphere. Deep convection driven by buoyancy generated by the radiative heating of atmospheric dust may be similarly important in the atmosphere of Mars but lacks a systematic description. Here we propose a comprehensive framework for this phenomenon of dusty deep convection (DDC) that is supported by energetic calculations and observations of the vertical dust distribution and exemplary dusty deep convective structures within local, regional, and global dust storm activity. In this framework, DDC is distinct from a spectrum of weaker dusty convective activity because DDC originates from pre-existing or concurrently forming mesoscale circulations that generate high surface dust fluxes, oppose large-scale horizontal advective-diffusive processes, and are thus able to maintain higher dust concentrations than typically simulated. DDC takes two distinctive forms. Mesoscale circulations that form near Mars's highest volcanoes in dust storms of all scales can transport dust to the base of the upper atmosphere in as little as two hours. In the second distinctive form, mesoscale circulations at low elevations within regional and global dust storm activity generate freely convecting streamers of dust that are sheared into the middle atmosphere over the diurnal cycle.

The Ensemble Mars Atmosphere Reanalysis System (EMARS) Version 1.0

The Ensemble Mars Atmosphere Reanalysis System (EMARS) dataset version 1.0 contains hourly gridded atmospheric variables for the planet Mars, spanning Mars Year (MY) 24 through 33 (1999 through 2017). A reanalysis represents the best estimate of the state of the atmosphere by combining observations that are sparse in space and time with a dynamical model and weighting them by their uncertainties. EMARS uses the Local Ensemble Transform Kalman Filter (LETKF) for data assimilation with the GFDL/NASA Mars Global Climate Model (MGCM). Observations that are assimilated include the Thermal Emission Spectrometer (TES) and Mars Climate Sounder (MCS) temperature retrievals. The dataset includes gridded fields of temperature, wind, surface pressure, as well as dust, water ice, CO2 surface ice and other atmospheric quantities. Reanalyses are useful for both science and engineering studies, including investigations of transient eddies, the polar vortex, thermal tides and dust storms, and during spacecraft operations.

Dusty Deep Convection in the Mars Year 34 Planet-Encircling Dust Event

Dusty convection, convective activity powered by radiative heating of dust, is a ubiquitous phenomenon in Mars's atmosphere but is especially deep (that is, impactful on the middle atmosphere) and widespread during planet-encircling dust events (PEDE) that occur every few Mars Years (MY). Yet the relative roles of dusty deep convection and global dynamics, such as the principal meridional overturning cell (PMOC) and the radiative tides, in dust storm development and the vertical transport of dust and water are still unclear. Here, observations from the Mars Climate Sounder on board Mars Reconnaissance Orbiter (MRO-MCS) are used to study dusty deep convection and its impact on middle atmospheric water content during the MY 34 PEDE (commenced June 2018). Additional context is provided by MRO-MCS observations of the MY 28 PEDE (commenced June 2007). This investigation establishes that a few, localized centers of dusty deep convection in the tropics formed in the initial phases of both PEDE simultaneously with a substantial increase in middle atmospheric water content. The growth phase of the MY 34 PEDE was defined by episodic outbreaks of deep convection along the Acidalia and Utopia storm tracks as opposed to less episodic, more longitudinally distributed convective activity during the MY 28 PEDE. The most intense convection during both PEDE was observed in southern/eastern Tharsis, where MRO-MCS observed multiple instances of deep convective clouds transporting dust to altitudes of 70-90 km. These results suggest that Martian PEDE typically contain multiple convectively active mesoscale weather systems.

The Aonia-Solis-Valles dust storm track in the southern hemisphere of Mars

Dust storm activity in the Aonia-Solis-Valles Marineris (ASV) region is analyzed using data collected from 8 Mars years of Mars Daily Global Maps. During L s = 120°-180°, dust storms within the ASV region tend to organize into dust storm sequences, making ASV an important storm track in the southern hemisphere outside the conventional dust storm season. In late southern winter, the ASV region is influenced by a combination of strong time-mean winds, synoptic eddies, and tidal winds. The ASV dust storm sequences can increase the background dust opacity and sometimes significantly influence the large-scale atmospheric thermal structure and planetary waves. They can be divided into two groups - one with large size and long duration; the other with small size and mostly short duration. The time series of storm area exhibits a pseudo-periodicity near 20 sols. This periodicity is similar to that found in eddy kinetic energy and traveling waves and to the Baroclinic Annular Mode of the terrestrial atmosphere.

Methane on Mars and Habitability: Challenges and Responses

Recent measurements of methane (CH4) by the Mars Science Laboratory (MSL) now confront us with robust data that demand interpretation. Thus far, the MSL data have revealed a baseline level of CH4 (∼0.4 parts per billion by volume [ppbv]), with seasonal variations, as well as greatly enhanced spikes of CH4 with peak abundances of ∼7 ppbv. What do these CH4 revelations with drastically different abundances and temporal signatures represent in terms of interior geochemical processes, or is martian CH4 a biosignature? Discerning how CH4 generation occurs on Mars may shed light on the potential habitability of Mars. There is no evidence of life on the surface of Mars today, but microbes might reside beneath the surface. In this case, the carbon flux represented by CH4 would serve as a link between a putative subterranean biosphere on Mars and what we can measure above the surface. Alternatively, CH4 records modern geochemical activity. Here we ask the fundamental question: how active is Mars, geochemically and/or biologically? In this article, we examine geological, geochemical, and biogeochemical processes related to our overarching question. The martian atmosphere and surface are an overwhelmingly oxidizing environment, and life requires pairing of electron donors and electron acceptors, that is, redox gradients, as an essential source of energy. Therefore, a fundamental and critical question regarding the possibility of life on Mars is, "Where can we find redox gradients as energy sources for life on Mars?" Hence, regardless of the pathway that generates CH4 on Mars, the presence of CH4, a reduced species in an oxidant-rich environment, suggests the possibility of redox gradients supporting life and habitability on Mars. Recent missions such as ExoMars Trace Gas Orbiter may provide mapping of the global distribution of CH4. To discriminate between abiotic and biotic sources of CH4 on Mars, future studies should use a series of diagnostic geochemical analyses, preferably performed below the ground or at the ground/atmosphere interface, including measurements of CH4 isotopes, methane/ethane ratios, H2 gas concentration, and species such as acetic acid. Advances in the fields of Mars exploration and instrumentation will be driven, augmented, and supported by an improved understanding of atmospheric chemistry and dynamics, deep subsurface biogeochemistry, astrobiology, planetary geology, and geophysics. Future Mars exploration programs will have to expand the integration of complementary areas of expertise to generate synergistic and innovative ideas to realize breakthroughs in advancing our understanding of the potential of life and habitable conditions having existed on Mars. In this spirit, we conducted a set of interdisciplinary workshops. From this series has emerged a vision of technological, theoretical, and methodological innovations to explore the martian subsurface and to enhance spatial tracking of key volatiles, such as CH4.

The Vertical Dust Profile over Gale Crater, Mars

We create a vertically coarse, but complete, vertical profile of dust mixing ratio from the surface to the upper atmosphere over Gale Crater, Mars, using the frequent joint atmospheric observations of the orbiting Mars Climate Sounder (MCS) and the Mars Science Laboratory (MSL) Curiosity rover. Using these data and an estimate of planetary boundary layer (PBL) depth from the MarsWRF general circulation model, we divide the vertical column into three regions. The first region is the Gale Crater PBL, the second is the MCS-sampled region, and the third is between these first two. We solve for a well-mixed dust mixing ratio within this third (middle) layer of atmosphere to complete the profile. We identify a unique seasonal cycle of dust within each atmospheric layer. Within the Gale PBL, dust mixing ratio maximizes near southern hemisphere summer solstice (L_s = 270°) and minimizes near winter solstice (L_s = 90-100°) with a smooth sinusoidal transition between them. However, the layer above Gale Crater and below the MCS-sampled region more closely follows the global opacity cycle and has a maximum in opacity near L_s = 240° and exhibits a local minimum (associated with the "solsticial pause" in dust storm activity) near L_s = 270°. With knowledge of the complete vertical dust profile, we can also assess the frequency of high-altitude dust layers over Gale. We determine that 36% of MCS profiles near Gale Crater contain an "absolute" high-altitude dust layer wherein the dust mixing ratio is the maximum in the entire vertical column.

Textured Dust Storm Activity in NE Amazonis-SW Arcadia, Mars: Phenomenology and Dynamical Interpretation

Dust storms are Mars's most notable meteorological phenomenon, but many aspects of their structure and dynamics remain mysterious. The cloud-top appearance of dust storms in visible imagery varies on a continuum between diffuse/hazy and textured. Textured storms contain cellular structure and/or banding, which is thought to indicate active lifting within the storm. Some textured dust storms may contain the deep convection that generates the detached dust layers observed high in Mars's atmosphere. This study focuses on textured, local dust storms in a limited area within NE Amazonis and SW Arcadia Planitiae (25°-40° N,155°-165° W) using collocated observations by instruments on board the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) satellites. In northern fall and winter, this area frequently experiences dust storms with a previously unreported ruffled texture that resembles wide, mixed-layer rolls in the Earth's atmosphere, a resemblance that is supported by high resolution active sounding and passive radiometry in both the near and thermal infrared. These storms are mostly confined within the atmospheric boundary layer and are rarely sources of detached dust layers. The climatology and structure of these storms is thus consistent with an underlying driver of cold air advection events related to the passage of strong baroclinic waves. While the properties of the studied region may be ideal for detecting these structures and processes, the dynamics here are likely relevant to dust storm activity elsewhere on Mars.

Polar vortices on Earth and Mars: A comparative study of the climatology and variability from reanalyses

Polar vortices on Mars provide case-studies to aid understanding of geophysical vortex dynamics and may help to resolve long-standing issues regarding polar vortices on Earth. Due to the recent development of the first publicly available Martian reanalysis dataset (MACDA), for the first time we are able to characterise thoroughly the structure and evolution of the Martian polar vortices, and hence perform a systematic comparison with the polar vortices on Earth. The winter atmospheric circulations of the two planets are compared, with a specific focus on the structure and evolution of the polar vortices. The Martian residual meridional overturning circulation is found to be very similar to the stratospheric residual circulation on Earth during winter. While on Earth this residual circulation is very different from the Eulerian circulation, on Mars it is found to be very similar. Unlike on Earth, it is found that the Martian polar vortices are annular, and that the Northern Hemisphere vortex is far stronger than its southern counterpart. While winter hemisphere differences in vortex strength are also reported on Earth, the contrast is not as large. Distinctions between the two planets are also apparent in terms of the climatological vertical structure of the vortices, in that the Martian polar vortices are observed to decrease in size at higher altitudes, whereas on Earth the opposite is observed. Finally, it is found that the Martian vortices are less variable through the winter than on Earth, especially in terms of the vortex geometry. During one particular major regional dust storm on Mars (Martian year 26), an equatorward displacement of the vortex is observed, sharing some qualitative characteristics of sudden stratospheric warmings on Earth.