Mitigation of environmental extremes as a possible indicator of extended habitat sustainability for lakes on 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 habitat sustainability within individual bodies of water. Environmental variables combine in the Bolivian Altiplano to produce some of the highest, least explored and most poorly understood lakes on Earth. Their physical environment of thin atmosphere, high ultraviolet radiation, high daily temperature amplitude, ice, sulfur-rich volcanism, and hydrothermal springs, combined with the changing climate in the Andes and the rapid loss of aqueous habitat provide parallels to ancient Martian lakes at the Noachian/Hesperian transition 3.7-3.5 Ga ago. Documenting this analogy is one of the focuses of the High-Lakes Project (HLP). The geophysical data we collected on three of them located up to 5,916 m elevation suggests that a combination of extreme factors does not necessarily translate into a harsher environment for life. Large and diverse ecosystems adapt to UVR reaching 200%-216% that of sea level in bodies of water sometimes no deeper than 50 cm, massive seasonal freeze-over, and unpredictable daily evolution of UVR and temperature. The HLP project has undertaken the first complete geophysical and biological characterization of these lakes and documents how habitability is sustained and prolonged in declining lakes despite a highly dynamical environment. The same process may have helped life transition through climate crises over time on both Earth and Mars.