Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10701720 | Icarus | 2012 | 5 Pages |
Abstract
Water is not currently stable in liquid form on the martian surface due to the present mean atmospheric pressure of â¼7Â mbar and mean global temperature of â¼220Â K. However, geomorphic features and hydrated mineral assemblages suggest that Mars' climate was once warmer and liquid water flowed on the surface. These observations may indicate a substantially more massive atmosphere in the past, but there have been few observational constraints on paleoatmospheric pressures. Here we show how the 40Ar/36Ar ratios of trapped gases within martian meteorite ALH 84001 constrain paleoatmospheric pressure on Mars during the Noachian era [â¼4.56-3.8Â billion years (Ga)]. Our model indicates that atmospheric pressures did not exceed â¼1.5Â bar during the first 400Â million years (Ma) of the Noachian era, and were <400Â mbar by 4.16Â Ga. Such pressures of CO2 are only sufficient to stabilize liquid water on Mars' surface at low latitudes during seasonally warm periods. Other greenhouse gases like SO2 and water vapor may have played an important role in intermittently stabilizing liquid water at higher latitudes following major volcanic eruptions or impact events.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Space and Planetary Science
Authors
William S. Cassata, David L. Shuster, Paul R. Renne, Benjamin P. Weiss,