Mars: new insights and unresolved questions

Abstract

Mars exploration motivates the search for extraterrestrial life, the development of space technologies, and the design of human missions and habitations. Here, we seek new insights and pose unresolved questions relating to the natural history of Mars, habitability, robotic and human exploration, planetary protection, and the impacts on human society. Key observations and findings include: – high escape rates of early Mars' atmosphere, including loss of water, impact present-day habitability; – putative fossils on Mars will likely be ambiguous biomarkers for life; – microbial contamination resulting from human habitation is unavoidable; and – based on Mars' current planetary protection category, robotic payload(s) should characterize the local martian environment for any life-forms prior to human habitation. Some of the outstanding questions are: – which interpretation of the hemispheric dichotomy of the planet is correct; – to what degree did deep-penetrating faults transport subsurface liquids to Mars' surface; – in what abundance are carbonates formed by atmospheric processes; – what properties of martian meteorites could be used to constrain their source locations; – the origin(s) of organic macromolecules; – was/is Mars inhabited; – how can missions designed to uncover microbial activity in the subsurface eliminate potential false positives caused by microbial contaminants from Earth; – how can we ensure that humans and microbes form a stable and benign biosphere; and – should humans relate to putative extraterrestrial life from a biocentric viewpoint (preservation of all biology), or anthropocentric viewpoint of expanding habitation of space? Studies of Mars' evolution can shed light on the habitability of extrasolar planets. In addition, Mars exploration can drive future policy developments and confirm (or put into question) the feasibility and/or extent of human habitability of space.

Editorial: Extremophiles: Microbial genomics and taxogenomics

“…The reach and impact of such research is now extending beyond our own planet, with increasing relevance in the cross-disciplinary fields of Astrobiology and Space Microbiology. The study of extreme environments on Earth and their inhabitants is one of the main pillars of research supporting the search for life on Mars, the exooceans of the icy moons of the solar system, and beyond (e.g., Jebbar et al, 2020 ; Taubner et al, 2020 ; Changela et al, 2021 ). Studies of terran extremophiles is also increasingly seen as useful for assisting space exploration in activities such as in situ resource utilization (ISRU; Cockell, 2010 ; Dhami et al, 2013 ; Changela et al, 2021 ).…”

Water is a preservative of microbes

“…Given the efficacy of water as a long‐term preservative (and assuming that alien life is indeed water‐based), such ‘biosignatures’ may even take the form of extant life. This could have implications on planetary protection procedures: care ought to be taken to consider long‐term preservation of cells in aqueous milieu to avoid contamination of Mars or other planetary bodies during space exploration (Changela et al ., 2021).…”

Microbial Survival in an Extreme Martian Analog Ecosystem: Poás Volcano, Costa Rica

“…To prepare for space missions with key goals to find signs of life on these extraterrestrial planets and moons, we must better understand how life in these environments may look like (Ehrenfreund et al, 2011). The search for signs of past life on Mars is a key NASA priority (National Research Council, 2011;Changela et al, 2021), demonstrated in 2021 by the arrival of the Perseverance rover on the Red Planet (Mangold et al, 2021). As of the time of this writing, neither extant life nor definitive signs of past life on Mars have been found; however, the habitability of Mars has been assessed to great detail (e.g., Cockell et al, 2012).…”