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Life on Mars? II. Physical restrictionsThe primary physical factors important to life's evolution on a planet include its temperature, pressure and radiation regimes. Temperature and pressure regulate the presence and duration of liquid water on the surface of Mars. The prolonged presence of liquid water is essential for the evolution and sustained presence of life on a planet. It has been postulated that Mars has always been a cold dry planet; it has also been postulated that early mars possessed a dense atmosphere of CO2 (> or = 1 bar) and sufficient water to cut large channels across its surface. The degree to which either of these postulates is true correlates with the suitability of Mars for life's evolution. Although radiation can destroy living systems, the high fluxes of UV radiation on the martian surface do not necessarily stop the origin and early evolution of life. The probability for life to have arisen and evolved to a significant degree on Mars, based on the postulated ranges of early martian physical factors, is almost solely related to the probability of liquid water existing on the planet for at least hundreds of millions to billions of years.
Document ID
Document Type
Reprint (Version printed in journal)
Mancinelli, R. L.
(NASA Ames Research Center Moffett Field CA United States)
Banin, A.
Date Acquired
August 21, 2013
Publication Date
March 1, 1995
Publication Information
Publication: Advances in space research : the official journal of the Committee on Space Research (COSPAR)
Volume: 15
Issue: 3
Subject Category
Distribution Limits
NASA Discipline Exobiology
NASA Program Exobiology
NASA Discipline Number 52-80
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