How NASA Makes Sure Human Missions Don’t Contaminate Destination Planets

In the near future, astronauts will return to Earth with fragments from deep space explorations. But precautionary measure should be taken to maintain scientific integrity of celestial samples and to make sure that they don't get contaminated with Earth-based organisms.

To address this concern, NASA released a report summarizing the result of a three-day workshop that convened global experts who investigated the different considerations for preventing biological cross-contamination of Earth and other worlds during human missions to different planets or celestial bodies.

For instance, astronauts on NASA's Asteroid Redirect Mission (ARM) will be returning to Earth with asteroid samples from cislunar space to find out more about the formation of the solar system. The "Journey to Mars" crew is also expected to carry samples from the Red Planet that could provide evidence of microbial life on Mars.

According to the report, these extraterrestrial samples are essential in answering scientific questions, which is why they should remain free from contaminants that humans or human space vehicles could introduce.

"We already have samples of Mars, and some comets and asteroids, here on Earth," Bette Siegl, program executive and planetary protection expert in NASA's Human Exploration and Operations Mission Directorate, said in a statement. "Some comet and asteroid samples were collected by spacecraft and returned directly to Earth, but many others that have spent millions of years in space regularly fall to Earth. These are quickly contaminated by Earth organisms once they hit the ground."

The report focused on two main areas of study: "forward contamination," which refers to the transport of Earth-based microbes to other celestial bodies, and "backward contamination," which is the possibility that extraterrestrial microbial life returned by a space mission could propagate on Earth.

The report also identified 25 gaps in knowledge about human-rated hardware systems, technologies and procedures for collecting samples and establishing decontamination procedures and acceptable contamination generation rates. Addressing the gaps would involve cooperation between planetary protection, science and engineering communities contributing to future human missions, NASA said.