Organic synthesis associated with serpentinization and carbonation on early Mars

Abiotic formation of organic molecules Mars rovers have found complex organic molecules in the ancient rocks exposed on the planet’s surface and methane in the modern atmosphere. It is unclear what processes produced these organics, with proposals including both biotic and abiotic sources. Steele et al . analyzed the nanoscale mineralogy of the Mars meteorite ALH 84001 and found evidence of organic synthesis driven by serpentinization and carbonation reactions that occurred during the aqueous alteration of basalt rock by hydrothermal fluids. The results demonstrate that abiotic production of organic molecules operated on Mars 4 billion years ago. —KTS

Microbes from Brine Systems with Fluctuating Salinity Can Thrive under Simulated Martian Chemical Conditions

The waters that were present on early Mars may have been habitable. Characterising environments analogous to these waters and investigating the viability of their microbes under simulated martian chemical conditions is key to developing hypotheses on this habitability and potential biosignature formation. In this study, we examined the viability of microbes from the Anderton Brine Springs (United Kingdom) under simulated martian chemistries designed to simulate the chemical conditions of water that may have existed during the Hesperian. Associated changes in the fluid chemistries were also tested using inductively coupled plasma-optical emission spectroscopy (ICP-OES). The tested Hesperian fluid chemistries were shown to be habitable, supporting the growth of all of the Anderton Brine Spring isolates. However, inter and intra-generic variation was observed both in the ability of the isolates to tolerate more concentrated fluids and in their impact on the fluid chemistry. Therefore, whilst this study shows microbes from fluctuating brines can survive and grow in simulated martian water chemistry, further investigations are required to further define the potential habitability under past martian conditions.

False biosignatures on Mars: anticipating ambiguity

It is often acknowledged that the search for life on Mars might produce false positive results, particularly via the detection of objects, patterns or substances that resemble the products of life in some way but are not biogenic. The success of major current and forthcoming rover missions now calls for significant efforts to mitigate this risk. Here, we review known processes that could have generated false biosignatures on early Mars. These examples are known largely from serendipitous discoveries rather than systematic research and remain poorly understood; they probably represent only a small subset of relevant phenomena. These phenomena tend to be driven by kinetic processes far from thermodynamic equilibrium, often in the presence of liquid water and organic matter, conditions similar to those that can actually give rise to, and support, life. We propose that strategies for assessing candidate biosignatures on Mars could be improved by new knowledge on the physics and chemistry of abiotic self-organization in geological systems. We conclude by calling for new interdisciplinary research to determine how false biosignatures may arise, focusing on geological materials, conditions and spatiotemporal scales relevant to the detection of life on Mars, as well as the early Earth and other planetary bodies.Thematic collection: This article is part of the Astrobiology: Perspectives from the Geology of Earth and the Solar System collection available at: https://www.lyellcollection.org/cc/astrobiology-perspectives-from-geology-of-earth-and-solar-system

Microbial habitability of the early Mars lacustrine environment sustained by iron redox cycling

Several studies have reported new data on the estimated compositions of chemical components at Gale crater; however, there is still a lack of information regarding potential past support of biomass and detectable biomarkers of ancient life. In this study we evaluate microbial habitability of early Mars constrained by the recently reconstructed water chemistry at Gale. The modeled community is based on Fe-metabolizing bacteria with the ability to utilize solid-phase iron oxides (e.g., magnetite) as an electron source or sink. Our results illustrate the plausibility of a sustained community in Gale Lake and provides suggestions for future modeled and laboratory-based studies to further evaluate the past habitability of Mars, biosignatures and their preservation potential, and hidden metabolic potential.One Sentence SummaryThis work provides an existence proof of habitability on early Mars and demonstrates modeling processes by which the habitability of extraterrestrial environments can be explored quantitatively.

3D Modeling of Supersaturated H2O/H2O2 on Early Mars Climate during the Noachia

<p>The climate of Mars during its first billion years is one of the most intriguing question in our understanding of the Solar System. The planet was host of a large amount of liquid water flowing on the surface throughout the Noachian era, approximatively 4Gya. Geomorphological observations is the main evidence for liquid water since valley networks and lakes are still visible on the surface, although dry nowadays.</p> <p>Different studies have tried to reproduce the conditions that may have occured on the planet, trying to find an atmospheric process or composition that could solve the Faint Young Sun Paradox. Theses modeling studies, through the use of 3-dimensional Global Climate Models struggled to warm sufficiently the past climate of Mars, even considering different greenhouse gases, the role of clouds, meteoritic impact or even volcanism (XXX). However, the presence of H2 could be an interesting solution for a sustainable warming as some recent studies suggest (Turbet and Forget, 2021). Another recent study (Ito et al. 2020) suggested that H2O2 might be a convincing candidate but has to be in high supersaturation ratio in the atmosphere, even though it only used a simplified 1D model and relatively high supersaturation levels.</p> <p>We try here to explore more in detail the scenario of supersaturated H2O2 and H2O, that also might be a specy able to provide a sufficient global warming under supersaturated conditions or through the formation of high altitude clouds. Since H2O is the major source of H2O2 in the atmosphere, it is important to assess whether the H2O content in the atmosphere is enough to provide high quantities of H2O2. We also try to constrain the theoritical supersaturation level of H2O/H2O2 that will allow the warming of the climate above 273K, but with a detailled 3D GCM simulation. Even if we do not tackle the question whether the supersaturation hypothesis is realistic or not, these results give a better understanding of  what would be Early Mars' climate under such conditions.</p>