• picture
  • picture
  • picture
  • picture
Public Radio's Environmental News Magazine (follow us on Google News)

Planetary Protection

Air Date: Week of

stream/download this segment as an MP3 file

When we think of the risks of space travel, we don’t usually think of the dangers we might pose to the extraterrestrial environment. But some scientists say we should make an effort to prevent our microbes from contaminating life forms that might exist on other planets, like Mars. Robin White reports.


CURWOOD: It’s Living on Earth. I’m Steve Curwood. Coming up: grape skins for your skin. It’s vino therapy.

First, the huge sheets of ice that were recently discovered on the surface of Mars have scientists suspecting we may find microbial life there. But, just as we shouldn’t go to a dinner party with an infectious disease, we need to make sure when we visit the red planet we don’t leave behind any unwanted germs. Robin White has our story.

WHITE: You don’t have to go to Mars to understand the problem of contamination. Time and again here on Earth we’ve introduced exotic species that have devastated the local fauna. Margaret Race is an ecologist who now works in the esoteric field of space contamination but she started out studying mud snails in San Francisco Bay.


RACE: I wouldn’t expect to find them along here, they don’t tend to come in over rocky areas.

WHITE: The East Coast mud snail was accidentally introduced here into the Bay after the Gold Rush. Race found that 150 years later it had driven the native Californian snail almost to the edge of existence by competing for its food and eating its eggs.

RACE: So we know if you move organisms from one place to another on Earth you can cause ecological disruption. So, when we go to the moon or to Mars or to other places in the solar system, we have to do our science responsibly. That means you don’t move organisms around unless you do it very carefully.

WHITE: We don’t know if there’s any life on Mars to disrupt. But the idea that there could be has become less outlandish based on discoveries made here on Earth. Scientists have found that bacteria are almost everywhere --living in hot ocean vents at high pressure, in battery acid and in Antarctic sea ice. These hostile places are similar to the conditions on some of the planets and moons we might visit.

COCKELL: EVA crew, have you completed depressurization to 5 psi?

RADIO: Yes we have – we’re confirming five psi depressurization complete.

WHITE: This is not preparation for a moonwalk. Everyone you’re hearing is right here on Earth. We’re in the far Canadian Arctic where scientists from NASA and other agencies are studying what it might be like to send humans to Mars. To help them do that they’ve set up a prototype Martian home away from home. Two scientists dressed in fake spacesuits are about to leave the cylinder’s airlock for a mockup Martian walkabout.

COCKELL: EVA crew, you are go for complete airlock depressurization

WHITE: There’s a comical aspect to the scene but underneath the dress up some real science is going on. Scientists come here to bleak, brown Devon Island every summer because it’s the part of the Earth that is perhaps most like Mars. There’s a 12-mile wide meteorite crater, similar to thousands which litter the surface of Mars. And like Mars, Devon Island is extremely cold and dry and gets a lot of ultraviolet radiation. Andy Scheurger is a scientist at the Kennedy Space Center in Florida. He’s here studying microorganisms such as staphylococcus, coliform and candida, which sometimes drop off the human body. He’s trying to find out if they’re able to colonize the soil around the research camp.


SCHUERGER: As you can see, the ground is pretty compacted and somewhat frozen, but I’m just scraping off the top three or four millimeters. … I’m harvesting from tire tracks from human footprints …

WHITE: Schuerger believes that human bacteria – unlike microorganisms that have evolved to live in extreme environments – won’t be able to take hold on Mars. He’s hoping his study here will help prove that.

SCHUERGER: If we can document that the human-associated microorganisms are unable to colonize this harsh environment, then it’s very unlikely that human activities on Mars would contaminate the landing site around a Mars base.

WHITE: Schuerger says most human microbes falling on the Martian surface would die off in minutes to hours.

Three thousand miles south of Devon Island at NASA’s Jet Propulsion Lab in Pasadena, California, scientists say we can’t afford to take any risks. Karen Buxbaum leads the agency’s planetary protection unit. She says it’s good science to make sure we don’t put any microbes on the surface of Mars.

BUXBAUM: We’re always on guard that something that we would take with us from one expedition would confuse the results from the next.

WHITE: It reminds her of the woozle story in Winnie the Pooh.

BUXBAUM: Pooh and Piglet are walking around this big tree in the snow looking for a woozle. And after they’ve gone in one orbit around the tree they see another they see two sets of footprints. And they continue to walk around and they see more and more footprints and they begin to wonder if they are seeing the tracks of more and more woozles.

WHITE: NASA is going to great lengths to make sure we don’t mistake our own biological footprints as evidence of Martian woozles. Wayne Shubert is in charge of the Jet Propulsion Lab’s clean rooms. That’s where spacecraft are designed.


To get inside we go through an elaborate decontamination process - stepping on sticky mats, putting on masks and robes and finally passing through the air shower.


SHUBERT: What we are doing is blowing air to remove any of the dust particles that may have inadvertently landed on our smocks and gloves and hats.

WHITE: Inside, the clean room is white and spotless. A gentle breeze carries away dust particles that might land on parts of a spacecraft. Older equipment such as the Mars Viking lander was sterilized with heat. But today’s sensitive electronics would be damaged by that. So now, NASA’s wiping with alcohol and using ultrasonic vibrations to shake loose microbes that might be attached to parts. Technicians test constantly to make sure they’re keeping down the numbers of microbes.


WHITE: A centrifuge spins samples taken from a supposedly clean spacecraft.

SCHUBERT: Detection of microorganisms is sort of the flip side of planetary protection. On one side we are trying to get rid of them but we need to be able to verify whether they are there or not so we need to be able to detect them, too

WHITE: Schubert’s team is looking for the molecule ATP which is found in every living cell. If ATP is present the samples actually light up, telling the technician there’s life there. And that happens all the time. It’s almost impossible to get anything completely clean. For a craft that’s going to land on Mars, NASA’s goal allows for up to 300 microbial spores per square meter of surface and 300,000 spores per spacecraft. That may sound like a lot, but it’s far cleaner than a hospital operating room. Karen Buxbaum says spacecraft designers go to great lengths to achieve that.

BUXBAUM: If they can avoid mechanical structures that have concave or hidden parts or right angle surfaces and, instead, have smooth surfaces that are easy to wipe clean, they’ll do that. We want to have things that avoid the same effect as dirt getting stuck in the corners when you’re washing the floor year after year.

WHITE: There are people who argue all these precautions are ridiculous. Bob Zubrin’s the founder of the Mars Society, a private organization promoting human colonization of Mars. He says a natural exchange of material between Earth and Mars has been happening for billions of years. When asteroids slam into planets they knock off bits of that planet’s rock. Those bits go flying around the solar system and sometimes land on other planets.

ZUBRIN: This natural transfer between Earth and Mars is one reason why the efforts to stop contamination are almost certainly completely futile. The bacteria have innumerable numbers of their own spacecraft and they’re not going through the quarantine.

WHITE: Many pounds of dust and rock from Mars do land on Earth each year and vice versa. Some argue that life on Earth might have been started by microbes that hitched a ride from Mars. But Karen Buxbaum says the transfer process can take thousands, even millions of years.

BUXBAUM: The types of accelerated processes that we do with our exploration is not the same as a process that takes place over geological time.

WHITE: We’d be moving organisms from one planet to another in a matter of months. We just can’t predict what would happen if we did introduce microbes to Mars in that way. Remember Andy Shuerger scraping tire tracks on Devon Island? Well, it turns out after many months of analysis he found that human microbes had survived the harsh winter in the Arctic soil. It doesn’t mean they would thrive in the extreme climate on Mars, but it does remind us that bacteria are tricky little devils. We don’t fully understand them and if we spread them around willy-nilly, we could do damage. Ecologist Margaret Race thinks that if we do find life on Mars exploration will become even more difficult.


RACE: If the life is truly Martian…essentially is distinct and unique and that raises something that’s ethical do we have a right to interfere with that and its existence and evolutionary trajectory. I don’t know the answer to that and I don’t know if any scientist or theologian does. It’s a question that stops you in your tracks.

WHITE: Hopefully, it stops us long enough to make sure we get it right. But almost all the scientists who work on the decontamination process say the human urge to explore is fundamental to who we are. They say we shouldn’t get so concerned about contamination that it stops us from venturing to other worlds.

For Living on Earth, I’m Robin White in San Francisco.

[MUSIC: Brian Eno, “Signals”, Apollo, EG Records (1983)]



Living on Earth wants to hear from you!

P.O. Box 990007
Prudential Station
Boston, MA, USA 02199
Telephone: 1-617-287-4121
E-mail: comments@loe.org

Newsletter [Click here]

Donate to Living on Earth!
Living on Earth is an independent media program and relies entirely on contributions from listeners and institutions supporting public service. Please donate now to preserve an independent environmental voice.

Living on Earth offers a weekly delivery of the show's rundown to your mailbox. Sign up for our newsletter today!

Sailors For The Sea: Be the change you want to sea.

Creating positive outcomes for future generations.

Innovating to make the world a better, more sustainable place to live. Listen to the race to 9 billion

The Grantham Foundation for the Protection of the Environment: Committed to protecting and improving the health of the global environment.

Energy Foundation: Serving the public interest by helping to build a strong, clean energy economy.

Contribute to Living on Earth and receive, as our gift to you, an archival print of one of Mark Seth Lender's extraordinary wildlife photographs. Follow the link to see Mark's current collection of photographs.

Buy a signed copy of Mark Seth Lender's book Smeagull the Seagull & support Living on Earth