The Space Reviewin association with SpaceNews

Mars sample tubes
Sample tubes cached by the Perseverance Mars rover for later return to Earth, an effort that requires following planetary protection protocols for both forward and backward contamination. (credit: NASA/JPL-Caltech/MSSS)

Why planetary protection matters to the future of space exploration

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The hiker’s motto you often hear cited when it comes to dealing with forays into the wilderness is, “leave only footprints, take only memories.” As humanity spreads outward into space we need to try and adopt something similar —perhaps adding, “take only memories, readings, and bring back a few samples.” We are moving outward to study worlds beyond our own. As such, it behooves us to do our best to not alter the very thing that we have gone out to study—if studying these places is why we go there in the first place, which it is.

When humanity heads to Mars and beyond in this and future centuries, we can’t just leave biohazards in a crater, however well contained. Forever is a long time.

Inevitably our space droids will break down and human astronauts will need to come home. Inevitably things will be left behind. Ideally, we leave behind things to further our studies. If weight and mission requirements call for leaving things behind, we should do so in the most responsible fashion possible. One thing in particular that we want to avoid doing is leaving terrestrial life behind.

Our record thus far has been rather good. Mars has lots of robots; some operating, others silent. With the possible exception of a few early Soviet probes, all others were sterilized before leaving Earth. The Moon is a somewhat different story. Half a century ago no one really thought there would be life there, and so far that is the prevailing assumption. The Apollo missions were barebones and a lot of things needed for human surface activities were left behind. Some things were crashed to create lunar quakes, which we then measured. Little if any sterilization of this hardware was done since the thinking at the time was that it was not necessary.

The catalog of human debris on the Moon ranges from the obvious (transport vehicles and tools) to the curious (golf balls, a feather, and a hammer) to the potentially hazardous. Strewn among the 400,000 pounds of lunar detritus are 96 bags of human waste. Some suggest we should check on them when we return. Why check? One obvious reason is to see what half a century of ±200-degree temperature swings and brutal ultraviolet radiation from the Sun does to them. Second while it is only theoretical, some thought has been given to what these extreme conditions might do to the microorganisms that were in the waste bags when they were left behind. Given the absurd extremes that some life forms on Earth thrive in, who knows what happened inside those bags. The astrobiology folks want to know.

Curiosity and 1960s mindsets aside, when humanity heads to Mars and beyond in this and future centuries, we can’t just leave biohazards in a crater, however well contained. Forever is a long time. And if the contents of waste bags—alive or inert—can affect the visited world after the container breaks down, well, that’s not why we went there. We’ll need a better way. The concept is called “planetary protection”. If you are a Star Trek fan this is the one of the precursors for the “Prime Directive”.

As is the case in our crowded, polluted, and rapidly warming world, we have stopped to ponder the wisdom of many of our prior decisions. As is the case with how we try to deal with our home planet, many people now ask how we could go to space responsibly. Planetary protection arose in the 1960s to protect the places we visit from earthly or “forward” contamination. It also embodied an approach for how to handle samples that we return to Earth to prevent “back contamination”.

The 1967 Outer Space Treaty requires nations to bear responsibility for their space activities and to avoid “harmful contamination” of celestial bodies. Since then, every space mission presumably has included measures to prevent such incidents. Yet today, some space stakeholders view the planetary protection model as an antique. Some feel that planetary protection, as currently applied, needs comprehensive international guidelines. Some people claim that current requirements could constrain the private sector. Taking concerns further, some people claim that the status quo of how we deal with preventing forward contamination could might even prevent humans from walking on Mars. Whether or not to debate these concerns and fears is a moot point. It’s a debate already underway in earnest.

The point in observing planetary protection today is that we are specifically looking for things on Mars that could possibly have existing life or evidence of past life. These signals and chemical structures are likely to be very fragile and can easily be contaminated by a single breath from a human researcher.

NASA’s Perseverance Mars rover is collecting samples in part to see if life has existed there. NASA plans to return those samples back to Earth as part of the Mars Sample Return program as soon as the early 2030s. The full array of planetary protection protocols is being observed, including how they are handled on Earth. Already, missions have brought back samples from comets and asteroids, so we have had practice in operating under these restrictions. So far they have all worked perfectly.

Some skeptics would counter that If at least 175 meteorites from Mars have struck Earth (that we know of), why should we worry now about bringing home rocks from Mars? Given the transit times between worlds—millions of years of intense solar exposure and high heat during atmospheric entry, among other factors—the probability that anything alive would survive is low, but not zero. The point in observing planetary protection today is that we are specifically looking for things on Mars that could possibly have existing life or evidence of past life. These signals and chemical structures are likely to be very fragile and can easily be contaminated by a single breath from a human researcher. Planetary protection also serves science as well as our ecosystem.

The need for planetary protection policy

Andy Spry, a senior scientist at the SETI Institute, framed planetary protection like dental hygiene: “It’s there, it’s inconvenient, but it’s really good to do.” Of course, planetary protection policies require constant updates. We developed them in the 1960s largely to address robotic exploration of other worlds. Landing humans on Mars wasn’t part of conversational reality then as it is now. Indeed, a recent SpaceNews op-ed made this point: “Under existing policies, no human mission would be allowed to venture to the surface of Mars.”

Aware of knowledge gaps, the National Academies of Sciences, Engineering, and Medicine recommended in 2018 that NASA update its planetary protection policies. NASA responded with a series of interim directives to support crewed missions to the Moon and Mars. NASA acknowledged the broad scope of these documents but determined they were necessary to release as framework guidelines. NASA also sought to confirm that planetary protection and human exploration of other worlds are compatible.

“Planetary protection does not say that humans cannot go to Mars,” Elaine Seasly, NASA’s Deputy Planetary Protection Officer, said in a presentation to Penn State’s Earth and Environmental Systems Institute. “We’re saying, ‘Yes, humans can go if we can monitor and manage contamination correctly.’ We’re shifting what we did with robotics in controlling contamination to managing and monitoring for crewed missions.”

Planetary protection issues to resolve

As more nations and commercial enterprises launch space programs, updated planetary protection policies are required. Three areas of interest involve international commitment, commercial space exploration, and new technologies.

An international commitment to transparency

More than 110 countries have signed and ratified the Outer Space Treaty. The Committee on Space Research (COSPAR) provides the most comprehensive international guidelines for planetary protection. Though most countries do, no country is legally required by these international treaties to adhere to the treaty or follow COSPAR’s recommendations. That leaves room for potential bad actors. “My concerns relate to China and Russia, who participate in a robust fashion at COSPAR but their actual follow through of regulations are wanting,” Mike Gold, chief growth officer at Redwire, said at the 2023 Humans to Mars Summit. NASA’s Artemis Accords seek transparency in the peaceful exploration of space. We must apply that transparency to planetary protection, a pursuit COSPAR can lead.

Cooperation with the private sector

Several companies have preliminary plans for commercial launches to Mars. The first human on the planet could be a private citizen. NASA and other international space agencies must work with private enterprise to develop agile policies that leverage innovation while protecting other worlds. The new space economy we now see unfolding has accelerated advances in many technologies. NASA, COSPAR, and other agencies can modernize international standards by flowing innovation through all parties and sharing best practices. The ability to detect contamination and characterize samples has vastly improved since the 1960s. Planetary protection policies need to take these advances into account.

Leveraging technology to keep pace

Space agencies test spacecraft surfaces for potential contamination before launching them. NASA is exploring how metagenomics might help conduct more specific risk-based assessments. The Jet Propulsion Lab conducts research in, among many disciplines, microbial reduction techniques and sample sterilization procedures.

Planetary protection can coexist with landing humans on Mars and bringing back rocks. It might be inconvenient, but it’s worth it.

As Seasly said in her presentation at Penn State, NASA is undergoing a “huge culture shift” regarding planetary protection. That’s vital. A new wave of collaborators—governmental and private—is leading space exploration in dynamic directions. They require a planetary protection framework that provides room for growth and innovation.

Concurrently, these new space-goers bear responsibility to protect Earth and the places they visit. We can do both with the right policies. Planetary protection can coexist with landing humans on Mars and bringing back rocks. As Spry said, planetary protection might be inconvenient, but it’s worth it.

Off we go

We face the issue of the “observer effect” whenever we reach out to a new environment, be it on Earth or on another world. As mentioned earlier, it is somewhat pointless to spend a lot of time and effort to go to a distant world to study it only to find out that we altered or contaminated the very thing we went to study.

Moreover, while science fiction is replete with constant alien invasions of Earth, the threat is not zero. And we will need to study many worlds and their life forms—or lack of them—before we can think of loosening these planetary protection protocols. Indeed, as we increase the number and diversity of worlds we visit these concerns may only become magnified.

As for sending people, and all of their biological companions, to other worlds, we have found ways to visit remote places on Earth without forward and back contamination. As we go, we’ll need to keep this in mind. But we will also need to understand what we find when we get there and how best to deal with this armed with data, not wild guesses.

But go there we will. Safely.

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