The Search for Alien Life Begins in Earth’s Oldest Desert
Mary Beth Wilhelm’s right arm shot out of the passenger window, and the convoy of vehicles behind her crunched to a stop. Spread among two trucks and an SUV, her four colleagues and I squinted and craned our necks, wondering what had caught her eye in the colorless wasteland of the northern Atacama Desert. She opened the door of our SUV and hoisted herself out.
The temperature was somewhere around 90 degrees Fahrenheit, and the mid-day gales were already picking up. Nothing beckoned. Nothing but tan spread out before us in every direction. I steeled myself against the wind, got out, and looked around.
Behind our convoy and down a hillside was the great salt flat called Salar Grande, a scorching, parched expanse about the size of San Francisco Bay. Ahead of my silver SUV, I saw a rolling Martian world of sand-colored rock spread beneath a blazing blue sky. No mosquitoes buzzed near our ears; no birds flew overhead. Wilhelm walked a few dozen feet away from the convoy, stopped, and stooped. Then everyone saw it.
A pebble field roughly the area of a two-car garage was dappled with chartreuse flakes: lichen. The first life we’d seen in days. Wilhelm crouched in the heat and squinted, flashing her hot-pink eyeshadow. She scooped some rocks into a sterile canister.
Later, Wilhelm would ship the rocks to her lab at NASA’s Ames Research Center, in Silicon Valley, where she works as an astrobiologist. She would scrape bits of lichen from the rocks, liquefy them, and sequence their DNA. She would do the same for microbes she collected from ravines, and preserved cells she scraped from salt rocks. In many places in the Atacama, such hardy creatures are the only life forms, and Wilhelm and other scientists think that they might be similar to the last surviving life on Mars—if Martian life ever existed.
The odds seem pretty good that we will find extraterrestrial life, someday. Everything Earth’s history has taught us suggests that once life takes hold, it is really, really hard to snuff out. Almost everywhere that astrobiologists like Wilhelm look—from sunless caves in the Italian Apennines to hydrothermal vents on the seafloor—they find something respiring and reproducing. Life is everywhere on this planet. Life can handle a lot. And yet we remain, so far, alone. No one has visited. Nobody has called. Nobody has turned up in our telescopes, our robotic instruments, or our collected space rocks.
In the Atacama, whose waterless, wind-worn landscapes mimic the surface of Mars, Wilhelm and her sunburned crew are mapping the edges of life’s domain, learning what life needs to survive, form communities, and produce future generations. And they are approaching the question they
