Is Mars’ Soil Too Dry to Sustain Life?

Life as we know it needs water to thrive. Even so, we see life persist in the driest environments on Earth. But how dry is too dry? At what point is an environment too extreme for even microorganisms, the smallest and often most resilient of lifeforms, to survive? These questions are important to scientists searching for life beyond Earth, including on the planet Mars. To help answer this question, a research team from NASA’s Ames Research Center in California’s Silicon Valley traveled to the driest place on Earth: the Atacama Desert in Chile, a 1000 kilometer strip of land on South America’s west coast.

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Credits: NASA Ames Research Center

This map of the Atacama Desert shows the change in annual precipitation from one end of the desert to the other. The aridity index mentioned is a value based on annual rainfall and water loss.

The Atacama Desert is one of the Earth’s environments that comes closest to the parched Martian surface. But the Atacama isn’t uniformly dry. When traveling from the relatively less dry southern end of the desert in central Chile to its extremely dry center in northern Chile, the annual precipitation shifts from a few millimeters of rain per year to only a few millimeters of rain per decade.

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The Martian surface may be even less hospitable to life than scientists had thought.

Ultraviolet (UV) radiation streaming from the sun "activates" chlorine compounds in the Red Planet's soil, turning them into potent microbe-killers, a new study suggests.