Mars Is Coming to Earth

By Bhavya Lal, Jeff Trauberman

Last week’s launch of NASA’s Mars rover Perseverance is the first leg of a four-stage, decade-long joint endeavor with the European Space Agency to bring back about half a kilogram of soil samples from Mars. If all goes well, the Mars Sample Return mission will ask one of the ultimate questions of space exploration: was there once life on Mars? Yet in seeking to answer this question, the mission also raises questions about protecting Earth and other celestial bodies from contamination. What if samples brought back from Mars contain pathogens harmful to the Earth’s biosphere? This is something scientists have considered since the 1950s under the rubric of “planetary protection.” This term refers, in part, to the practice of avoiding contamination of the Earth by extraterrestrial biological organisms, known as backward contamination.

The first time NASA had to take this risk seriously came when Apollo 11 astronauts splashed down in the Pacific Ocean on July 24, 1969, fresh from their successful moon landing. The original plan was to lift the return capsule onto the recovery ship with a crane, and then transfer the astronauts directly into a controlled quarantined environment. But the waves were too rough and officials didn’t they think could safely lift the capsule up without it swinging back into the aircraft carrier. So they ignored protocols and Navy divers opened the capsule’s hatch to hand the astronauts their biological isolation garments. In the process, they exposed the ocean to the inside of the capsule and the three astronauts. Had there been harmful organisms on the moon, they might have escaped into the Pacific Ocean and potentially spread worldwide.

Of course the Apollo astronauts didn’t return to Earth with pathogens from the moon. Fifty years later, the Mars mission—the first mission to bring material from another planet back to Earth—raises once again the potential of exposing the biosphere dangerous organisms from space. 

But it isn’t only backward contamination of Earth that officials are concerned about (although clearly it’s of significant interest to humans). Forward contamination, or the contamination of other celestial bodies by terrestrial lifeforms or organic compounds, is also a key component of planetary protection. If spacecraft aren’t adequately sterilized before they reach other bodies in the solar system, scientists may not know if any life discovered actually originated there.

Say the Perseverance rover finds the bacterium E. coli on Mars. How are scientists to know that it did not originate in the intestines of an engineer who worked on the rover? What if Earth-based microbes on the planned Europa Lander mission wipe out native life on this fascinating moon of Jupiter, eliminating any chance that future missions would find life in the relatively warm and active oceans there?

In addition to maintaining the scientific integrity of the search for extraterrestrial life, some experts have raised ethical and environmental concerns related to forward contamination, and advocate for keeping celestial bodies in undisturbed, pristine condition, as well as preventing the disruption of any extraterrestrial microbial lifeforms that may be discovered.

But planetary protection policy also has detractors, some of whom believe that the policy makes it impossible to conduct the very research these rules are intended to protect. Are efforts to prevent forward contamination inhibiting the search for extraterrestrial life by inflating the cost of space missions? As humans expand their footprint in the solar system, how much—if any—contamination is too much, how should this bioburden be reduced, and what is the appropriate price tag to reduce the risk of forward and backward contamination?

Contamination regulation

Planetary protection policy, as practiced today, is rooted in the late 1950s when scientists became concerned that improperly supervised space exploration could affect the integrity of scientific investigation. Microbes or organic constituents carried on spacecraft from Earth could contaminate and thus jeopardize current and future scientific experiments, in particular those focused on discovering extraterrestrial life. At the behest of several scientific organizations, including the US National Academy of Sciences, the international nongovernmental organization Committee on Space Research (COSPAR) created international standards and guidelines to protect the biological and environmental integrity of other solar system bodies for future science missions.

In the mid 1960s, the United Nations deliberated and finalized the Outer Space Treaty. The treaty, signed in 1967, has been ratified by the United States and is now the law of the land. Article IX of the treaty, concerned with “avoiding harmful contamination” of celestial bodies and “adverse changes” to the environment of Earth, afforded a legal foundation for COSPAR’s planetary protection policy (although neither of these terms is actually defined in the treaty). Abiding by COSPAR policy is an accepted way of complying with Article IX obligations, but there is no legal requirement for any nation, including the United States, to follow COSPAR policy.

Abiding by COSPAR policy is an accepted way of complying with Article IX obligations, but there is no legal requirement for any nation, including the United States, to follow COSPAR policy.

Today, consistent with COSPAR policy, NASA’s planetary protection policy attempts to meet two goals: preserve the integrity of Earth’s biosphere from backward contamination, and protect the biological and environmental integrity of other solar system bodies from forward contamination for future science missions. NASA implements its planetary protection policy through the Office of Planetary Protection (not to be confused with the agency’s Planetary Defense Coordination Office, which focuses on monitoring and mitigating potentially dangerous asteroid impacts on Earth). Planetary protection missions are categorized based on the threat they may pose to the integrity of science or Earth’s biosphere. Based on this categorization, NASA policy requires the use of varying approaches toward sterilization, and sets permissible microbial levels on spacecraft to mitigate the risk of contamination.

This protection doesn’t come cheap. Although NASA doesn’t publish the cost of its planetary protection efforts, historical estimates show that for the most sensitive missions, planetary protection may comprise about 10% of the total cost. Some experts contend that it is not the direct cost but the indirect cost that is problematic. As one member of this camp put it, “The cost of a ball-and-chain isn’t the cost of the ball and the chain, but what one cannot do because one has on a ball-and-chain.” These experts believe planetary protection restrictions limit the quality and quantity of science by, for example, preventing a mission from targeting a habitable destination because it would cost too much to sterilize the instruments to the degree required by COSPAR policy.

Some small tardigrades for man, one giant biological mess for the moon

Research conducted by the IDA Science and Technology Policy Institute shows that the environment for US planetary protection regulations has changed dramatically in recent years. One of the most prominent changes is the rise of commercial deep space activities in a domain traditionally dominated by government programs. There exist no guidelines for how (or even if, legally speaking) the private sector should ensure planetary protection, nor is there agreement on which government agency should regulate private companies and how. Some representatives contend that NASA policy does not and should not apply to the private sector.

Two examples illustrate why this is important. In 2018, a few days before the inaugural launch of the SpaceX Falcon Heavy launch, Elon Musk, the company’s chief executive, tweeted “Falcon Heavy sends a car to Mars.” The payload, a used Tesla Roadster, had not been sterilized for Mars, and the Federal Aviation Administration (FAA), the government organization that typically licenses private-sector launches, did not have a process in place to ensure that the Roadster was meeting the nation’s legal obligations—or if it even had to. After determining that the vehicle would not, in fact, be going to Mars, regulators approved the launch.

More recently, in April 2019, a SpaceX rocket launched a private spacecraft to the moon that was carrying, among other things, microscopic organisms called tardigrades. The US government found out about this stunt not because SpaceX or the Israeli spacecraft owner SpaceIL filed planetary protection paperwork identifying the payload, but because the American nonprofit that put tardigrades on the spacecraft announced it after the probe crash-landed on the moon. These remarkably hardy microorganisms now on the lunar surface are, according to the space mission’s organizer, likely still alive. Both these incidents revealed the challenges facing authorities as a larger number of more diverse organizations conduct more activities in space that could have serious scientific and legal implications.

Even when they are not purposely sending lifeforms into space, a greater number of countries are conducting robotic deep space missions, as was evident with the recent launches of the United Arab Emirates’ Hope and China’s Tianwen-1 missions to Mars. Some countries may not have the kind of experience needed to implement complex and expensive planetary protection guidelines. Governments (and private organizations) are also considering sample return missions, such as last week’s Mars 2020 mission, from celestial bodies that might harbor or once harbored life. Sample return protocols aren’t defined well enough to ensure that if life is brought back, it can be contained. Here, too, there have been a number of “fails,” starting with the Apollo program, for which planetary protection protocols were written but not precisely followed.

There are also now government and private sector plans for human missions to Mars. Current limits on the acceptable risk of biological contamination were developed for robotic missions. The limits on the amount of bioburden allowed on a spacecraft are inconsistent with the number of microbes in the human body. A single human carries trillions of microbes, and can’t be baked, irradiated, or bathed in chemicals to destroy them.

A single human carries trillions of microbes, and can’t be baked, irradiated, or bathed in chemicals to destroy them.

A final factor with consequences for planetary protection is the emergence of a growing number of new scientific approaches and technologies, to both sterilize systems and better detect extraterrestrial life. Changing current approaches and implementation procedures may not only improve compliance with planetary protection policy but also be more cost effective.

Time to review

Although NASA has begun to address many of these challenges (as evidenced by the release of NASA Interim Directives on planetary protection a few weeks ago), together these factors argue for a more comprehensive review of the nation’s approach to planetary protection at the federal level, starting with five considerations.

1. Types of harm. Some experts agree that NASA’s efforts to prevent forward and backward contamination are an appropriately narrow interpretation of Article IX of the Outer Space Treaty. Others note that the goal of protecting the integrity of future scientific missions by minimizing the potential for forward contamination exceeds the treaty’s “harmful contamination” provision; they argue that any policy to reduce an already small risk of harming future science is overly burdensome. Yet another group of experts makes the case that the current goals are too narrow, and that the scope of planetary protection policy should be expanded to avoid harmful contamination of any kind—not just contamination that might spoil future scientific missions on celestial bodies. Their arguments are grounded in environmental and ethical reasons. What should be the appropriate focus of a planetary protection policy?

2. Appropriate level of stringency. Even if policy-makers agree that the goal of planetary protection from forward contamination should remain unchanged, is the sterilization approach appropriate, and are implementation procedures (such as placing specific limits on the amount of bioburden on spacecraft) ineffective or too costly? Private-sector missions, for example, tend to reflect cost-sensitive business plans, which means they may not be able to afford the expensive procedures required by NASA’s planetary protection policy. Should the government lower its bar for planetary protection, or at least provide performance-based targets instead of specific procedures to meet targets?

3. Preparation for safe sample return. Some experts argue that no materials (neither samples originating on those bodies nor humans journeying to those bodies) should be returned from celestial bodies until it is demonstrated either that the likelihood of that body containing life is sufficiently low, or that the life that might be brought back will not cause adverse effects on Earth. Most experts agree that samples should be returned to Earth, but have concerns that governments are unprepared to ensure fail-safe sample containment or provide a clear approval process for return. What are the appropriate levels of safeguards to prevent backward contamination?

4. Guidance and oversight for the private sector. Planetary protection experts express concern that if private companies do not follow planetary protection policy, they could cause irrevocable harm to future scientific endeavors. On the other hand, some representatives of private companies disagree with the current implementation of planetary protection policy, noting that by virtue of its restrictions, it obstructs the search for life. It is also not clear how the US government’s Outer Space Treaty obligations under Article IX or Article VI (which calls for government “authorization and continuing supervision” of nongovernmental entities) will be met or addressed. Also unclear is whether the FAA’s authority over launch approval includes, or should include, the ability to specifically require that private companies follow NASA planetary protection policy (or some other set of directions) on an ongoing basis. How should the private-sector launching missions with planetary protection concerns be regulated?

5. Participation from all relevant stakeholder groups. There are some concerns that experts from disciplines outside astrobiology—such as technologists and engineers, advocates for settling extraterrestrial bodies, and biosafety and biosecurity researchers—do not have enough of a role in making decisions related to planetary protection. Many of these experts observe that simply increasing access to and participation in forums provided by NASA and COSPAR may not adequately address their concerns, and they would like a seat at the decision-making table. How should a larger cross-section of the community engage in discussions related to planetary protection?

A confluence of factors suggests that focused US policy leadership on planetary protection is needed now. Ambitious interplanetary space missions are moving toward reality. Advances in diverse technical disciplines are proceeding rapidly, including in space technology, astrobiology, and planetary protection techniques. Finally, new governmental and private-sector groups are fast emerging within the planetary space community. Addressing the planetary protection policy questions identified above will ensure that the United States continues to lead in the future. A visionary US planetary protection policy can simultaneously ensure public health, advance scientific research, promote private sector space activity, and enable a vigorous human space exploration program.