EXPLORING THE EARLY NOACHIAN TERRAINS OF MARS

Understanding how planetesimals form into planets is crucial to understanding early solar system evolution. In the absence of direct observations or suitable laboratory experiments for the earliest history (i.e., Hadean Eon ~4.6 to 4.0 Ga) of Earth, much of what is known about terrestrial-planet formation comes from computer simulations. Presently, terrestrial scientists are trying to locate, collect, and analyze ancient rock layers that might provide clues to the evolutionary history of Earth. Unfortunately, most if not all Hadean rocks and their ~ 500 million geological and planetary environmental records have been destroyed. This missing period of Earth’s history is a critical missing link in understanding how the atmosphere, oceans, and differentiated layers of the core, mantle, and outer crust developed on the planet. Without ancient rocks to examine, scientists have no direct evidence on how fast the surface environment evolved, how and when the transition took place from a rocky planet to one with an ocean and atmosphere, or when conditions became hospitable enough for the Earth to support life. In search of evidence to address these major questions, we propose exploring the extremely ancient terrains (> 3.9 Ga) on Mars, which include Terra Cimmeria, Terra Sirenum, and Arabia Terra, for answers. These ancient terrains display distinct magnetic anomalies and relatively large tectonic structures that extend farther back in time than the giant four impact basins: ~2,300-km-diameter (east to west) Hellas, ~1,500-km Isidis, ~1,800-km Argyre, and controversial ~1,600-km Chryse. Exploring these ancient environments, which are distinctly older than those that have been observed thus far by landing, roving, orbiting, and now hovering spacecraft, offers the best opportunity to increase our understanding of how a planet and its atmosphere form and to evolve during the earliest phase of evolution, and whether life ever existed on Mars.