Noachian environments on Mars and the possible emergence of life

Life seems to make planet Earth a unique place in the universe, but favorable conditions for its development certainly exist and must have existed elsewhere and almost at any time across the Universe. In the Solar System, Mars is the nearest planet that seems promising for finding a second example where life may have surged and evolved. In contrast to Earth, present Mars is probably too cold and dry, and with a thin atmosphere to permit life forms to duel on its present surface. However, early in its history, Mars was climatically much like the young Earth, when life emerged. In spite of the much smaller size compared to Earth and its greater distance to the Sun, Mars could have harbored life if certain fortuitous conditions coincided there at the right time and place. Favorable habitable conditions must include a denser and warmer atmosphere that buffers global climate, permanent bodies of liquid water in which chemical evolution can occur, a global magnetic field to protect the planet from damaging radiation, chemical availability, volcanism that recirculates gases and water and creates new heterogeneous environments, and impacts that melting ice and can form microenvironments with hydrothermal activity. The scars leftover by abundant running and stagnant water on the Noachian lands of Mars support the full attainment of those conditions and hence, most probably also the emergence of Martian life. In this work we examine four central issues of the Noachian history (~4.5 to 3.7 Ga) of Mars, germane to the eventual appearance of life: 1) The nature and evolution of early global processes such as planetary accretion, building of a dense atmosphere, the presence of a global magnetic field and a magma ocean, and the effects of the Late Heavy Bombardment, that brought abundant organic compounds and volatiles to the early Mars; 2) the thermal evolution of the crust, including plate tectonics and volatile-rich volcanism; 3) the Martian liquid paleohydrology (lakes, rivers and putative oceans); and 4) the role of minerals in prebiotic chemical evolution potentially leading to the appearance of living organisms on Mars.