Species are fragile but life is tough. It’s tenacious. It’s endured, thrived, gone forth and multiplied for billions of years, with no sympathy for the weak—natural selection does not permit it. What lives today was built to last, able to withstand the heavy bombardment of asteroids and the slow drift of continents. The genetics of every creature are like roadmaps of the hard lessons learned across eons.
Life in the context of exploration is a terrifying in its power. The explorers of the New World didn’t come alone, and the microbes they carried ravaged the native peoples, who lacked natural defenses to European disease. That is another hard lesson learned, and as humans and our robotic emissaries press forth into the solar system, we must protect Earth from the similar introduction of some tiny alien visitor malignant to our kind, as well as protect other worlds from the tiny creatures of our own planet.
At NASA, this job falls to Catharine Conley, head of the agency’s Office of Planetary Protection. Her job is to make sure the spacecraft we send to other worlds are free of microbial stowaways. It’s not an easy job, life itself rugged and relentless, and it’s not always a popular job, the process of spacecraft sterilization being expensive in remorseless budget environments. And yet here and there, if life exists there, her labors keep planetary ecosystems separate and undisturbed.
Cassie Conley. Credit: Paul Alers/NASA
Species are fragile but life is tough.
“Before we launch a spacecraft to another world, the first question is what do we know about that world,” she tells NOW.SPACE. Bodies like the moon have no possibility of Earth life surviving on it, growing, and causing problems down the line. The planetary protection plan for robotic missions to such places is simply one of documentation. “Tell us what your robot did and where you left it,” says Conley. “Tell us when you drop circuit boards in a particular place so that someone won’t come along later and think ‘We’ve found gold! Lead! Cadmium! We’ve got to mine this!’ We want to keep track of what happens so that we are well informed for when future missions go out and find something peculiar.”
If, on the other hand, scientists don’t know enough about the destination, but conclude that it seems hospitable to Earth-life or life of its own—ocean worlds like Europa and Enceladus are top contenders in our solar system—missions there must take decontamination measures based on probability. “We protect those places by ensuring that the mission doesn’t introduce Earth-life into the potential habitats at a level of confidence that is considered appropriate to what we know,” she says.
Mars Opportunity planetary protection: Credit: NASA/JPL
Those measures can be taken both before and after launch. The prelaunch decontamination recipe calls for, among other things, baking spacecraft parts at 110- to 125-degrees-Celsius for several days. This is largely unchanged since the Sputnik days, though the stringency of NASA’s decontamination efforts have fallen since the Viking missions, when decontamination meant baking an entire spacecraft, as opposed to parts of it. (“Viking was the epitome of planetary protection,” says Conley.)
Post launch, outer planets missions can take into account the oftentimes harsh radiation environments, as well as orbital assists. Juno, for example, had to travel inside the orbit of Venus before it got out to Jupiter. Sunlight, as the saying goes, is the best disinfectant. It’s hard to get more sunlight than that.
NASA will be exploring Europa in force with a multiple flyby mission (popularly called Clipper), a lander, and quite possibly a surface penetrator. The whole point of our invading robot army is an expectation that Europa’s subsurface ocean will not only be habitable but actually be inhabited. Because the lander will be setting down on the surface and possibly interfacing with the ocean, planetary protection measures are paramount.
Viking Lander preparing to be baked. Credit: NASA
The team behind Juno, the spacecraft currently in orbit around Jupiter, had to account for the possibility of the spacecraft going astray and crashing into Europa. What would they do? It turns out, not much. The team ran orbital simulations and realized that the spacecraft would be traveling 22 kilometers per second on a direct collision with the surface. Juno would be vaporized on impact, and with it, the stowaway life forms it might be carrying. They were able to incorporate this into their probability calculations.
“The Europa lander is required to ensure that it has a probability of contaminating a Europan ocean of less than one in 104, and that needs to be demonstrated before the mission is allowed to launch,” says Conley. “They have a strategy for how they’re going to do that. There are different options for how much they will do the reduction before launch, and how much they’re going to try to do the reduction after launch. But as long as they have demonstrated that they meet the probability, then there is no problem.”
To that end, the Europa lander will have a self-destruct switch. NASA has shied away from including the science fiction staple in its spacecraft because there’s little chance of the Klingons getting access to our rovers and using them against us. In this case, the self-destruct isn’t to protect our spacecraft from extraterrestrials, but rather, to protect extraterrestrials from our spacecraft.
Phoenix Mars Lander under planetary protection protocols. Credit: Lockheed Martin
Jet Propulsion Laboratory, NASA’s research and development center, went to Sandia National Laboratories to find a suitable self-destruct mechanism. If the lander has an off-nominal event—i.e., if it’s about to crash into Europa—it will automatically self-incinerate, instantly disinfecting at 500-degrees over a span of half a second. The skycrane, after setting the lander successfully on the surface, will fly away, as was famously done for the Mars rover Curiosity. Unlike the Curiosity skycrane, however, the Europa one will also self-destruct after flying away. In the hopeful event of a successful landing and mission, the Europa lander is still doomed to fiery decontamination. It is not a long-term mission like Cassini or the Mars rovers. It will live fast and die young.
“It’s funny because no mission designer, no spacecraft engineer, wants their mission to die. But a lot of them are also pyromaniacs,” Conley says with a laugh. The Europa surface spacecraft will be destroyed no matter what—and that is a happy ending. The fear is anything else happening. “If they were planning to do an incendiary explosion on impact,” says Conley, “and they impact and the explosion hadn’t happened… that would be unfortunate. That would be the worst case scenario for a Europa lander.”
The Europa lander will live fast and die young.
If the self-destruct fails, the mission team would have to do an analysis of how many stubborn organisms were actually delivered to Europa, and to what environments on their new castaway planet they are going to be exposed. A report of their findings would be submitted to the International Council for Science and the United Nations.Article 9 of the Outer Space Treaty warns against the harmful contamination of other planetary objects and adverse changes to the environment of the Earth itself from the introduction of extraterrestrial matter. In context, this refers to biohazards—replicating organisms from somewhere else that are brought here.
“We actually had to do that for the Mars Polar Lander which impacted Mars in 1999,” explains Conley. NASA had two missions to Mars fail during the faster-better-cheaper era: the Polar Lander and the Climate Orbiter. (“We got none out of three.”)
“That’s not the worst-case scenario,” says Conley. “The worst case scenario doesn’t happen until you bring a sample back to Earth. You bring a sample back to Earth from Europa or Mars or Enceladus or somewhere else that has life when you thought it didn’t, and you let it out, and it causes problems.”
Such reports are necessary because no spacecraft can be perfectly sterilized. In any event, it’s a near-certainty that we’ve contaminated Mars previously. “At the time of Viking, scientists thought that baking a spacecraft at 110 Celsius—a little above the boiling temperature of water—would kill any organism from Earth. They soon realized that wasn’t the case,” Conley says.
“We’re learning more about Mars that suggests that it is perhaps more habitable than we thought for particular types of Earth organisms,” she continues. “We’re learning more about the organisms also—and it turns out the area of separation between the capabilities of those organisms and the environments that we identify on Mars—that separation is getting less. They’re getting closer to overlapping even at the surface, even at the equator.”
If there is native life on Mars or Europa, it will likely have endured and adapted to hardships, just as has life on Earth. As we search for the answer to “Are we alone?” NASA and the burgeoning international space community will only grow more ambitious, with penetrators punching through the Europa ice shell and submarines swimming the seas of Titan. The work of the Office of Planetary Protection grows only more challenging and important.
More life can be found under a rock than on it. One day our explorers will turn up the stone that changes everything. Catharine Conley and her team make sure that when that happens, we neither damage nor interfere with the native Martians, Europans, or Enceladites. Four billion years from now, they will surely thank us for that.