Dynamics of declining lake habitat in changing climate

We illustrate the impact of climate variability on lake habitat at high altitude as a proxy to the evolution of declining lakes on Mars. The geophysical environment at the summit lake of the Licancabur volcano (5970 m) in the Central Andes of Chile and Bolivia was monitored between 2002 and 2006. The lake’s environment presents analogies with Mars at a time when the planet was transitioning from a wetter to a drier, colder climate: thin atmosphere, high solar irradiance, low ozone, high daily and yearly temperature fluctuations with low averages, ice, reduced yearly precipitation, and volcanic geology. The Licancabur lake is also located in a region impacted by climate change resulting in enhanced evaporation and strong negative water balance that rapidly modifies lake habitat. Data show that although the decline is not monotical, interannual fluctuations in precipitation, water balance, major ion concentration, and pH are well marked. Microorganisms dwelling near or at the water/atmosphere interface are exposed to a solar irradiance 160% that of sea level. Maximum averaged UVB peaks at 4 W/m2 and shorter (260–270 nm) radiation is also detected at the surface. The thin and cold atmosphere generates sudden and significant inverse relationship between UV radiation and temperatures. In this cold, unstable environment the lake ecosystem is abundant. In addition to adaptation strategies, data suggest that the timing of key cycles is a critical factor in life survival and provide important information on the lake habitability and life survival potential on Mars as the climate changed.