Active Ground Patterns Near Mars' Equator in the Glen Torridon Region of Gale Crater

On Mars, near the equator, much of the terrain in Gale Crater consists of bedrock outcrops separated by relatively smooth, uniform regolith surfaces. In scattered sites, however, distinct patterns—in the form and texture of the ground surface—contrast sharply with the typical terrain and with eolian bedforms. This paper focuses on these diverse, intriguing ground patterns. They include ∼1 to >10 m-long linear disruptions of uniform regolith surfaces, alignments, and other arrangements of similar-sized rock fragments and shallow, ∼0.1 m-wide sandy troughs 1–10 m in length. Similar features were recognized early in the Mars Science Laboratory (MSL) mission, but they received only limited attention until Curiosity, the MSL rover, encountered striking examples in the Glen Torridon region. Herein, the ground patterns are illustrated with rover images. Potential mechanisms are briefly discussed in the context of the bedrock composition and atmospheric conditions documented by Curiosity. The evidence suggests that the patterns are active forms of spontaneous granular organization. It leads to the hypothesis that the patterns arise and develop from miniscule, inferred cyclic expansion and contraction of the bedrock and regolith, likely driven by oscillating transfers of energy and moisture between the atmosphere and the terrain. The hypothesis has significant implications for studies of contemporary processes on Mars on both sides of the atmosphere-lithosphere interface. The ground patterns, as well as ripples and dunes formed by the wind, constitute remarkable extra-terrestrial examples of granular self-organization, complex phenomena well known in diverse systems on Earth.A. G. Fairén was supported by the ERC-CoG #818602. M.-P. Zorzano has been partially funded by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu”-Centro de Astrobiología (INTA-CSIC) and by the Spanish Ministry of Science and Innovation (PID2019-104205GB-C21). Last but not least, B. Hallet and R. S. Sletten gratefully acknowledge sustained funding for their work through the MSL mission in a NASA grant awarded to MSSS

Numerical modelling for the hydrothermal activity & habitability of Mars

Modern space and planetary explorations are enthusiastically searching for extraterrestrial biosignatures, and even intelligence in our cosmic neighbourhood. Mars is the epicentre of planetary research and astrobiology, as during ancient geological periods, the Red Planet should have had a thicker atmosphere, and exhibits evidence for ancient aqueous, volcanic and hydrothermal activity. Such physical processes that persist on a planetary body through geological time increase the probability of the emergence and evolution of antediluvian microbial species. However, present-day Mars is a cold and arid desert. So, could the Red Planet host evidence of extinct or/and even extant microbial life? To contribute towards deciphering this mystery, this PhD research focuses on determining the thermodynamic and hydrological evolution, and subsequent habitability of ancient hydrous environments on Mars. Martian habitability, especially during the planet’s ancient geological history, has not been decisively established yet. Moreover, quantitative analyses and models for the ancient or present bioenergetic potential on Mars are scarce. Water – rock interactions enduring in longlived hydrothermal settings on Earth yield appreciable quantities of chemical nutrients that support microbial species under hydrothermal conditions. Through this perspective, the habitability of simulated Martian hydrothermal systems deserves to be computed and analysed. This PhD research explores simulated volcanogenic and impact-induced hydrodynamics on Mars, and the astrobiological potential of such ancient or more recent Martian aqueous environments via computational scenarios. High-resolution numerical simulations for the aqueous circulation and thermodynamics in a variety of putative Martian hydrothermal systems have been constructed and interpreted. Rock permeability, porosity, temperature, pressure, enthalpy, heat capacity, and thermal conductivity comprise governing physical parameters for the duration and mechanics of the hydrothermal cycle in each simulation. Therefore, the presented thermodynamic simulations explore thoroughly the evolution and duration of putative impact-induced or magmatic-induced hydrological systems on Mars from the pre-Noachian to the late Amazonian. The thermodynamic results of these models are then used as input conditions in further computations for Martian water – basaltic rock reaction pathways and their subsequent bioenergetic yield (habitability). Eventually, quantitative habitability assessments are conducted based on the energy – chemical nutrient availability and on the thermal constraints that cumulatively render these environments habitable or uninhabitable for hypothetical lithotrophic microbial species in the Martian subsurface. In parallel, NWA 8159 (shergottite) and Lafayette (nakhlite) Martian meteorite samples were examined through Scanning Electron Microscopy (SEM) analysis to identify their Martian mineralogies, and detect alteration phases – fluid compositions that have affected these basaltic rocks on Mars, or on Earth due to weathering processes after their fall. Petrological analyses provided additional insights into the geochemical composition and evolution of these Martian rocks. Furthermore, image processing on acquired SEM-BSE montage maps of the NWA 8159 and Lafayette samples revealed the porosity of these Martian rocks, and subsequently constrained and enhanced the hydromechanic and habitability models of this PhD research. The hydrothermal and habitability simulations indicate that the Martian basaltic subsurface could have supported hydrogenotrophic microbial life for periods ranging from 0.1 Myr to 3 Myr under preserved hydrothermal conditions. The modelling results additionally suggest that deeper basaltic domains (subsurface depth ≥ 1.5 km) in large impact craters (100-, 200-km diameters) or intrusive volcanic rock settings, could comprise the most promising sites for astrobiological research. The ideal habitable thermal range in which nutrients, and specifically H2, are released in appreciable amounts through ongoing water – rock reactions is from 50 °C to 121 °C. Under such hydrothermal conditions, the Martian subsurface is modelled able to support the survival and growth criteria of hydrogenotrophic life. However, aqueous circulation and geochemical reactions should endure for an average minimum period of 120 Kyr to support microbial growth, and conceivably, the microbial colonization of the Martian subsurface. The numerical simulations of this research support that cold aqueous flows and short-induration hydrological systems on Mars are unable to support the survival of potential microbial species for a period ≥ 2 Kyr. Finally, even in the most optimistic thermodynamic scenarios for Martian habitability, microbial species in the deep Martian subsurface cannot be supported for a period longer than 1 – 2 Myr, after hydrothermal activity has halted. This indicates that any potentially inhabited environments on Mars could have supported microbial life only for an average maximum period of 3 – 4 Myr. Conclusively, planetary environments beyond Earth that may have been hosting hydrothermal or aqueous activity continuously for Myr or even Gyr (i.e.: the Jovian and Kronian moons, beneath their icy crusts) comprise the most habitable extraterrestrial niches of the Solar System, and promising sites for astrobiological findings

Martian subsurface cryosalt expansion and collapse as trigger for landslides

On Mars, seasonal martian flow features known as recurring slope lineae (RSL) are prevalent on sun-facing slopes and are associated with salts. On Earth, subsurface interactions of gypsum with chlorides and oxychlorine salts wreak havoc: instigating sinkholes, cave collapse, debris flows, and upheave. Here, we illustrate (i) the disruptive potential of sulfate-chloride reactions in laboratory soil crust experiments, (ii) the formation of thin films of mixed ice-liquid water “slush” at −40° to −20°C on salty Mars analog grains, (iii) how mixtures of sulfates and chlorine salts affect their solubilities in low-temperature environments, and (iv) how these salt brines could be contributing to RSL formation on Mars. Our results demonstrate that interactions of sulfates and chlorine salts in fine-grained soils on Mars could absorb water, expand, deliquesce, cause subsidence, form crusts, disrupt surfaces, and ultimately produce landslides after dust loading on these unstable surfaces