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Abstract 

The Atacama Desert, Chile, is among the least habitable environments on the planet largely because of its extreme aridity; nevertheless, ecosystems continue to function in many locations there, at least intermittently when water is available. This study addresses the question of whether dew could ever form at high-elevation sites in the Atacama region. Two distinct modeling approaches were used to model dew formation on volcanoes using data from climate stations at 2950, 4720, and 5820 meters above sea level (m.a.s.l.) to help explain the presence of a recently discovered simple microbiological ecosystem existing in soils from 5200 to over 6000 m.a.s.l. on other volcanoes in the region. The first model uses field data for air temperature and relative humidity to calculate dew point (temperature at which dew would form) and compares it with field soil temperatures at different depths as well as with air temperature. The second model calculates and compares the maximum amount of water vapor that air of the respective air temperature at each elevation could hold (saturation vapor pressure) to the actual amount of water vapor present (actual vapor pressure) at the time of measurement. Both models show that dew formation would not occur regularly at any of the elevations or months measured in the field. However, given that there are times just before sunrise when conditions are close to allowing for dew, it is possible that a rare and atypical weather event may result in dew formation. Given the known ability of organisms adapted to arid environments to survive long periods of no water availability, it is possible that this intermittent access to liquid water is sufficient to sustain the ecosystem found on high elevation volcanoes in the Atacama region.