Can the Combination of Extremes Protect Life: Clues from Altiplanic Lakes and Implication for Early Mars

The impact of individual extremes on life, such as UV radiation (UVR), temperatures, and salinity is well documented. However, their combined effect in nature is not well-understood while it is a fundamental issue controlling the evolution of the Habitable Zone (HZ) and that of the aqueous Habitable Zone (aHZ) within individual bodies of water on Earth. It is also central to the understanding of lakes habitability on Mars as the climate conditions declined 3.5 billion years ago. Environmental variables combine in the Bolivian altiplano to produce some of the highest, least explored and most poorly understood lakes on Earth. The geophysical data we collected on four of them located between 4,500 m and 6,014 m shows that many of these conditions bear similarity to environments thought to have existed and potentially supported life on ancient Mars. Their study suggests that a combination of extreme factors does not necessarily translate into a harsher environment for life and that habitability in martian lakes might have endured well into the climate change of the Noachian/Hesperian transition.