HYDROTHERMAL MARS: HOW THE MARTIAN CRUST COULD PROVIDE ESSENTIAL CLUES TO ABIOGENESIS

One of the most amazing discoveries in the last 15 years of Mars exploration has been the detection of thousands of hydrothermal deposits exhumed from the martian subsurface by impact and erosion. Infrared remote sensing of these exhumed terrains has revealed the presence of Fe/Mg-rich phyllosilicates such as smectites and mixed-layer clays, chlorite- and serpentine-group minerals, prehnite, silica, carbonate and zeolite. Widespread hydrothermal activity in the ancient martian subsurface, and in some deep basins, likely mirrors hydrothermal processes on the early Earth. In such settings, interaction of alkaline fluids with ultramafic crust resulted in energy sources for primitive prokaryotic life here.

With the exception of occasional climate excursions, Mars may have been cold, arid, oxidizing and generally inhospitable at the surface for much of its history. However, conditions below ground were far more clement. If life ever formed in hydrothermal or subsurface environments on Mars, it could have remained stable for geologically significant periods of time. In some cases on Earth, subsurface prokaryotes may have existed in situ for 100 Myr to 1500 Myr. But, more important than the potentially risky goal of searching for extant life on Mars is the fact that Mars could teach us a tremendous amount about the prebiotic chemistry in mafic-ultramafic hydrothermal systems.

Only rare traces of Earth’s geologic record are preserved from the time of life’s emergence, over 3800 million years ago. Consequently, what little we understand about abiogenesis on Earth is based primarily on laboratory experiment and theory. The best geological window into early Earth might actually be Mars’ crust, which is more ancient than our own, and contains clear evidence for past hydrothermal environments analogous to those where chemosynthetic life may have first taken hold on Earth.

 In this presentation, I will describe the geology and mineralogy of hydrothermal deposits on Mars, and the role hydrothermal systems might have played in the habitability of Mars – both subsurface and surface.