Reduced albedo on early Mars does not solve the climate paradox under a faint young Sun

Abstract

Context. The presence of liquid water on the surface of early Mars and Earth is difficult to reconcile with the reduced solar luminosity at 3.8 Ga. and before, which would have imposed mean temperatures below freezing all over both planets. For the case of Earth, it has been recently suggested the hypothesis that less continental area and limited cloudiness during the Archaean may have reduced planetary albedo and thereby increased surface warming by sunlight. Aims. Here we analyze whether this novel solution explaining warming conditions on the early Earth could be applied to early Mars. Methods. We use an energy balance climate model in our calculations. Results. Our results show that early Mars could have been kept warm as long as there was a nearly global ocean and relatively sparse cloud coverage. This result is internally inconsistent, and also incompatible with most of the observed geological evidence. Conclusions. Reduced albedo is not a suitable solution for the faint young Sun problem in the case of early Mars. The combination of climatic and geochemical models is essential for understanding the stability of liquid water during the Noachian.