Wet and cold thick atmosphere on early Mars

Abstract
The evidence of past fluvial activity on the surface of Mars indicates that since the end of the intense period of crater formation liquid water has flowed on the surface. There is also evidence that indicates that Mars has maintained a cold dry climate over this same time. This apparent contradiction can be resolved if the early martian atmosphere is thick (>100 hPa) but cold (less then -20C). Snow based hydrological cycles such as found in the dry valleys of Antarctica can then explain both the fluvial features and the cold arid climate. Life could flourish under such conditions.