The case for a Martian origin for Earth life

Classical prebiotic chemistry, which has for the last half century explored the reactivity of small organic molecules in glassware environments under the control of chemists, has left unanswered multiple paradoxes with respect to the origins of life. Many of these can be approached, and possibly solved, by placing organic molecular reactivity within the context of the rocks, minerals, hydrosphere, and atmosphere of a prebiotic earth. This new direction in prebiotic chemistry is discussed here, with special emphasis on the role of minerals in constraining the inherent propensity of carbohydrates to devolve to form unproductively complex mixtures of materials. We focus in particular on minerals containing the elements boron and molybdenum, which is produced in discontinuous synthesis model for the emergence of RNA as the first Darwinian molecule. Further, the role of desert environments to manage the "water paradox" is discussed in the context of many classes of processes that have been proposed to deliver RNA under prebiotic conditions. If current models are correct to suggest that early Earth may have been largely flooded at the time when life originated, Then those desert environments may not have been available. However, the inventory of water on Mars has always been less than on Earth and, as Kirschvink has pointed out, intercourse between the two planets was frequent during the time when life is emerging on either planets. This suggests that desert like environments may have been present on early Mars, if they were not present on early Earth.