The Dry Edge of Life: Studying “Martians” in Chile

I recently spent a week with a group of astrobiologists studying life in the Atacama Desert of northern Chile.

This is extraordinary, because the Atacama is the driest place in the world. The average annual rainfall is one millimeter, and decades can go by between rain events.

There’s not much life to study. It’s too dry for plants and animals to survive in the desert’s hyperarid core. There are no insects, no lizards, no birds, no rodents. No trees, no shrubs, no cacti. Not even lichen. Nothing but dirt, rocks and salt flats.

To a large extent, the landscape has gone unchanged for 10 to 15 million years. It looks like pictures of Mars. (Related: “Chile Desert to Prepare Robot for Life on Mars.”)

NASA scientists interested in what life may have looked like on ancient Mars therefore spent several years trying to find bacteria living in the Atacama. (Related: “Viking Mission May Have Missed Mars Life, Study Finds.”)

The salt flats turned out to be the key. They’re not exactly flat—they’re filled with bizarre, knobby rocks made of halite (table salt). The locals call these knobs flores (“flowers”), because they grow over time. Rocks like these don’t form anywhere else on Earth—nowhere else is dry enough.

In 2005, in an unnamed salt flat near the site of a former nitrate mine, Jacek Wierzchos, a researcher from Madrid, discovered a novel species of photosynthetic bacteria living inside these salt rocks.

Occasionally at night, when the relative humidity in the air increases sufficiently, the halite rocks absorb moisture from the atmosphere, and microscopic pockets of liquid brine form inside them. Because halite is translucent, it allows some sunlight to penetrate into its interior, enabling photosynthesis while screening out harmful UV radiation.

The findings from studies of these halite flowers may help guide the future search for life on Mars. Conditions similar to those in the present-day Atacama may have existed on Mars in the past.

For more information, check out my field reports on the Astrobiology Magazine website.

Changing Planet

Meet the Author
Science writer and photographer Henry Bortman is the field research editor for the NASA-sponsored website Astrobiology Magazine. His work takes him on scientific expeditions to extreme environments around the world. He reports on research aimed at understanding the limits of life on Earth and finding evidence of life on other worlds.