Hunt for ET: You Can Help Search Earth's Deserts for Alien-Like Life

The Atacama Desert is one of the harshest environments on Earth. Martin Bernetti/AFP/Getty Images

Scientists love visiting the most extreme places on Earth to try to get a better sense of what life could be like on other, less hospitable planets—but there are only so many scientists, and they only have so much money to spend on adventures.

So one of them decided to crowdsource her quest. The result is Rockiology, a citizen science project run by Jocelyne DiRuggiero, a biologist at Johns Hopkins University who studies extremophiles, the scientific term for bacteria that live in extreme conditions.

Usually, that means DiRuggiero and her colleagues travel to Chile's Atacama Desert to hunt for tiny, plant-like microbes hiding out on the surface—or even the inside—of rocks in the harshest deserts on the planet. "When things get really, really dry those microbes find refuge inside rocks," DiRuggiero said. "It's the best place for them to be protected from high solar radiation and wind."

To do so, she's learned their wants and needs. "I have to think like a bacterium," DiRuggiero said. "I try to think where would be the best place—where I would be protected, but where I would get enough light from the sun to do photosynthesis and where I can get enough water." The rocks she (and the bacteria) are looking for include common types, like granite, quartz and sandstone, but they're marked by a greenish sheen that gives away their inhabitants.

And now, anyone who wants to take a hike in the desert can try their hand at tracking down these hardy organisms, which could teach scientists not only about life on other planets, but even about life on ours in an age of climate change.

"This is absolutely about astrobiology," DiRuggiero said. "This is one of the closest environments we have on Earth to Mars, it's extremely dry and the soil has the same qualities," she added of her usual study site in the Atacama. The bacteria she studies could teach us about even more distant worlds as well, planets orbiting other suns.

Read more: When Will We Find Aliens? NASA Is Studying Earth to Find Signs of E.T. On Distant Planets

Those planets turn out to be easier to study the closer they are to their stars—but of course, closer also means hotter and drier. So the question becomes when do we stop looking, how close is too close to host living things, DiRuggiero said. "How close can we get to the star and still have enough water on the planet for life to exist?"

But water shortages aren't only an exotic problem: They also bedevil life here on Earth, and that will only get worse as climate and land use continue to change. "Big parts of the world are going toward deserts," DiRuggiero said. "We need to understand, what are microbial communities doing in those deserts—because they are the only inhabitants of those deserts."

Rocks found in the Atacama Desert could help scientists understand life on other planets. Martin Bernetti/AFP/Getty Images

The scientists, of course, are just stopping by, staying long enough to collect the samples they need and then returning to more welcoming corners of the planet. "The desert's pretty amazingly beautiful, and it's very rugged," DiRuggiero said. "You feel very small in big deserts like this." But the work means driving where there are no roads, carrying all the water she needs for any hike. "We have to be very careful not to be dehydrated, that's the most important," DiRuggiero said. "And then at the end of the day, you can't take your boots off because you're still outside!"

Prospective citizen scientists should also be armed with plenty of water, as well as a smartphone that can record the GPS coordinates of where the sample was found. DiRuggiero's site includes a map of target deserts, a guide to the type of rocks most commonly colonized and a guide to recognizing the green streaks the bacteria leave and collecting samples. For her, it's important to teach participants how to take samples efficiently. "They just need to chip a little bit of the rock to see if there's colonization," DiRuggiero said. "We don't need to smash hundreds of rocks in big quantities."

Rockiology participants then send her a photo of the sample so she can decide whether she wants to study it more detail. In her lab, DiRuggiero studies the rocks themselves as well as the microbes that live in them. For life here on Earth, that means better understanding what makes different groups of bacteria thrive under different conditions, which could tell us what keeps these tiny ecosystems going under desert conditions.

And when it comes to finding life on distant planets, studying rocks found here could help us recognize extraterrestrial life when it's staring us in the face. That's because DiRuggiero and her team can look at the traces the microbes leave behind—both the chemicals they create and the changes they make on the surface of the rock. Those are signs scientists can then look for on other planets, in our own solar system and beyond.