Planet Protector

Catharine Conley has one of NASA’s most unusual job titles: Planetary Protection Officer. She works to protect our solar system from invading aliens—but not the kind you see in movies. The aliens that keep Conley awake at night are microbes.

If microscopic organisms exist on nearby planets, moons, or space rocks called asteroids, they could accidentally hitch a ride on spacecraft sent to explore these places. When the spacecraft return to Earth, the alien stowaways could cause trouble here at home.

As we explore space, we also run the risk of contaminating other worlds with microbes from Earth. It’s up to Conley to stop both scenarios from happening. Science World spoke with Conley to find out how 
she does her job.

It would be really disheartening to discover life on Mars, only to find out later that it was actually just microbes we brought from Earth. And if the wrong kind of microbes got to Mars, they could cause big problems. For example, Mars soil is about one percent perchlorate—a chemical that future astronauts could potentially use as an energy source. Earth has microbes that like to eat perchlorate. If we accidentally bring one of them along to Mars, we could destroy that energy source before we got a chance to use it.

No. Many Earth organisms can live in space. Microscopic animals called tardigrades have survived on a satellite—an artificial body orbiting Earth—in space for 10 days. Fly larvae have survived for two years on the outside of the International Space Station.

During the Viking program in the 1970s, NASA sent landers to Mars to look for life. Before launch, scientists killed all microbes on them by baking the spacecraft in a giant oven. 

Viking data revealed that most of Mars is cold and dry, so Earth life probably couldn’t survive there. Now that we know that, scientists carefully clean Mars spacecraft, but they don’t have to go to the extreme of baking them. Scientists also keep spacecraft away from the more hospitable places on Mars where Earth life might be able to grow and spread, such as sites that might have liquid water. That will be the case with the European Space Agency’s ExoMars lander, which should reach Mars this October. I’ve been involved in planetary protection for the mission.

Europa, a moon of Jupiter, is one of the best places to look for life beyond Earth. Its surface is a thin shell of ice, believed to cover a giant ocean. The ocean probably has formations similar to Earth’s hydrothermal vents, openings in the seafloor that release heated water. Someday we could send a spacecraft to drill through Europa’s ice and dive into the ocean. We’ll want to make sure we’re not accidentally bringing Earth life along for the ride.