Habitability on Mars: Comparison with the Early Earth
WHENFebruary 16, 2021 5pmWHEREZoom WebinarWHOCenter for Space ScienceOpen to the Public
Mars today is a cold and hostile desert but in its past it hosted plentiful water – without ever becoming covered by an ocean. There is abundant geomorphological and mineralogical evidence for past water on its surface as demonstrated by orbital and in situ measurements. Moreover, water ice has been detected at its poles. Water is an essential ingredient for habitability and the emergence of life. Organic molecules are equally important and, as documented at Gale Crater, at least organics of likely extraterrestrial origin were deposited on Mars’s surface in the past and toady, as on Earth.
Early Earth was a completely different planet to the one we know today. Similar to Mars it had CO2 atmosphere and was volcanically active. Similar to Mars it had liquid water, but in this case the early Earth was an ocean planet with small protocontinents capped by exposed volcanoes while Mars was a land-locked planet. Early Earth had a requirements for the emergence of life – water and organic molecules in contact with rocks and energy sources (heat, UV light, chemical) and it appears that Mars did about 4 billion years ago. While the Earth remained eminently habitable and conducive to the evolution of complex life as we know it today, this was not the case for Mars. Its habitable environments were separated from each other in time and space; there was a lack of connectivity of habitats. This meant that, if life did emerge, it remained at a very primitive stage of evolution.
Frances Westall, CNRS-Centre de Biophysique Moléculaire, Orléans, France
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