Origin of Life on Mars: Suitability and Opportunities

Abstract

Although the habitability of early Mars is now well established, its suitability for conditions favorable to an independent origin of life (OoL) has been less certain. With continued exploration, evidence has mounted for a widespread diversity of physical and chemical conditions on Mars that mimic those variously hypothesized as settings in which life first arose on Earth. Mars has also provided water, energy sources, CHNOPS elements, critical catalytic transition metal elements, as well as B, Mg, Ca, Na and K, all of which are elements associated with life as we know it. With its highly favorable sulfur abundance and land/ocean ratio, early wet Mars remains a prime candidate for its own OoL, in many respects superior to Earth. The relatively well-preserved ancient surface of planet Mars helps inform the range of possible analogous conditions during the now-obliterated history of early Earth. Continued exploration of Mars also contributes to the understanding of the opportunities for settings enabling an OoL on exoplanets. Favoring geochemical sediment samples for eventual return to Earth will enhance assessments of the likelihood of a Martian OoL.

Keywords: CHNOPS; Mars; astrobiology; early Earth; exoplanets; origin of life; prebiotic chemical evolution; sample return; transition elements.

Figure 1

Some example groups that have spearheaded investigations into the origin of life, showing accelerated intensity in the study of prebiotic organic evolution pathways, subsequent to the findings of Miller–Urey experiment in 1953 [18] (Each block is one decade, e.g., 2010 = 2010 to 2019).

Figure 2

Examples of enriched occurrences of some key transition elements discovered during the MSL mission, compared to the Earth’s average crustal concentrations, SNC meteorites [125], and a typical Martian global soil composition [123]. “Mars enrichments”: nickel maxima (except for meteorites) for three rover missions (MER, MSL); Cu at Gale crater [196]; Zn also all three missions, plus up to 8000 ppm in Gale; boron at Gale [198].

Figure 3

Evidence for similar amorphous material at widely separated sites: Esperance coating [191] at Endeavour crater compared to JohnKlein (JK) and its amorphous component [224] plus salts at Gale crater (85% JK AmC, 13% MgSO₄, 2% CaCl₂).

Figure 4

Diverse thermokarst ponds in Sheldrake River valley near Nunavik, Quebec in the Canadian subarctic (56° N) [253]. Photo-credit, J. Comte (Institut national de la recherche and Centre for Northern Studies).

Figure 5

Partial pressure of pure H₂O, setting the limit on boiling (brines will be stable to higher temperatures).

Figure 6

Freezing-point depression for salty brines, which extend the mobility of aqueous media in a sub-zero environment, but do not fully extend the temperature range for metabolic functionalities.

Figure 7

Mudcrack pattern of the “Old Soaker” slab (Sutton Island member of Murray Formation), a red mudstone overlying gray sandstone as imaged by the primary camera of the MSL Curiosity rover, sol 1555) [275].