Mary Beth Wilhelm is a planetary scientist and astrobiologist at NASA Ames Research Center in Mountain View California. She specializes in studying areas on Earth that have climates and landscapes similar to those found on Mars -- and that means some of the driest and most remote parts of the planet. She talked to us about what it's like to travel to the coldest and hottest places in the world where, in some cases, rain only falls once every decade.
What exactly does a planetary scientist do?
My work is a combination of fieldwork and lab work and a lot of writing. Way more writing than I ever expected going into the sciences. In my research, I'm mostly interested in searching for the signs of life on Mars. You could describe me as an astrobiologist -- understanding the origin of life on Earth and looking for it outside of Earth.
How can you find life on other planets by looking at Earth?
Basically I use these really Mars-like places on Earth as a testbed to understand how all of the components that make up life are preserved in those types of environments. One of the most Mars-like places is the Atacama Desert. You can look at dryness as a function of precipitation or you can look at it as the availability of water for life. In Yungay, a region in northern Chile, it only rains there once a decade, about 2 - 5 mm. Barely enough to even form a puddle. There's no plants, no lichens or mosses. I'm doing a study right now and don't even see evidence for activity of soil bacteria. Even the coastal city of Antofagasta in northern Chile, which is on the Pacific Ocean, is about 30 times dryer than the Mojave Desert.
How did it get so dry there?
It has to do with the Andes. They're tall and block the trade winds that go from the Atlantic towards the Pacific. Hot dry air descends on the desert. Offshore on the Pacific Ocean the currents come up from Antarctica they're cold and therefore the air doesn't pick up any moisture. It's' been like this for millions of years. It has been Mojave Desert-level dry for a hundred million years, a couple rain storms per year. And then it's been even drier, 100 times dryer than the Mojave, for 10 to 15 million years.