A new deal for the human exploration of Mars

Abstract

Common ground between human spaceflight and astrobiology can be used as the foundation for a new deal in the exploration of Mars that will allow stakeholders to reach critical astrobiological goals while supporting safer human exploration.

Planetary protection guidelines are designed to prevent forward-contamination of another world with terrestrial biomaterials and to protect Earth from back-contamination with hypothetical lifeforms from another world¹. Many national space agencies, including NASA and ESA, follow a stringent decontamination process during the preparation, assembly and launch of their spacecraft, and various private space companies–at least in the USA–have started to be engaged in the planetary protection debate^2,3. However, the situation is rapidly evolving, with publicly declared ambitions to send crewed missions to Mars, possibly within the next two decades⁴. In this context, current planetary protection guidelines may be insufficient. It is inevitable that terrestrial microorganisms will accompany human crews to Mars and may find ways to adapt and survive⁵, because it is impossible to ensure that all human-associated processes and operations are conducted within entirely closed systems¹: accidental release of biomaterials is bound to happen as a result of human activity⁶. With global dust storms, this could rapidly turn into a planetwide spread of contaminants.

Urgent action is required: by taking precautionary steps now, we can avoid contaminating a possible biosphere we have barely started to seek, perhaps altering it with unknown consequences. Despite the public misconception that humans have been searching for life on Mars for decades, since the pioneering Viking 1 and 2 lander missions in the 1970s, we have in fact planned missions specifically focused on biosignature detection only recently: NASA’s Mars2020 Perseverance rover landed on Mars in 2021 (Fig. 1), and ESA’s Rosalind Franklin ExoMars rover will hopefully follow in 2029. Therefore, there are still many unknowns that do not allow us to quantify the risk and consequences that terrestrial life could bring to a Martian ecosystem. The argument exists that the human exploration of Mars would be biologically reversible, in the same way as human exploration of the Dry Valleys of Antarctica is not considered problematic for astrobiology exploration there⁷. However, Mars is a different planet, with a possibly entirely separate genesis, and it would be risky simply to assume that the biocontamination of Mars would be reversible by applying containment and recoverability: if it turns out that it is not, there will be no second chance.

Fig. 1. Perseverance acquired and stored this double-sample of the Jezero Crater delta front between July and August 2022.

The sampled rock was a fine-grained sedimentary rock formed about 3.7 billion years ago as mud settled in an evaporating saline lake, with high concentrations of organic matter. Therefore, the samples record a potentially habitable environment and have high biosignature preservation potential. To clarify this potential, samples will be brought to Earth as the next greatest step in Mars astrobiology, without altering the pristine Mars environment. Inset: Perseverance’s twelfth core sample, the second from the double-sampling, in its sample cache.

If life emerged on Mars, whether we are related to such life through planetary exchange of prebiotic or biomaterials in the early Solar System, or whether a Martian biosphere arose from a separate genesis, will have profound implications for our assessment of how abundant life could be beyond Earth. In the former case, Mars would provide us with a unique opportunity to study ancestral terrestrial metabolic pathways, given that the enduring active geology that makes our planet so bio-diverse is also responsible for erasing the record of our origins over time, whereas Mars has changed relatively little in the past 3.5 billion years. On the other hand, if we are not related to Martian life, then by introducing biocontaminants on Mars we run the risk of potentially altering or losing forever precious evidence of the nature of an alien coevolution of life and its environment, and its role in the transition between prebiotic chemistry and biochemistry.

Before sending astronauts to Mars, we need to characterize the levels of potential contamination that humans may carry through laboratory and fieldwork data, understand how fast this contamination could spread across the surface, and very precisely define what an ‘acceptable risk’ in a biological contamination protocol consists of. We should also establish the characteristics of the surface and subsurface environments that constitute the astrobiological baseline of the landing sites prior to the introduction of terrestrial biomaterials, and what that baseline needs to be for the abundance of organic compounds and other biomarkers that could be used to track terrestrial contamination⁸. And we need to detail operational processes and develop the required hardware to set foot on Mars without jeopardizing the search for life or harm an indigenous ecosystem⁹. We have yet to collect and analyse a body of relevant data and observations to address these fundamental questions. After decades of scientific and technological effort from hundreds of thousands of researchers around the world, and the integrated national investments in programmes over decades it has taken to determine that Mars was once or may still be habitable, all these yet-undefined constraints should make it clear that racing to Mars with humans might be imprudent.

What is more, as long as we do not know the characteristics of a putative Martian biosphere, there is a possibility that life will find astronauts before astronauts find life¹⁰. If Martian life is present, back-contamination is as likely as forward-contamination. The life that astrobiology is searching for on Mars could equally be harmed by humans, or harm us. Furthermore, after a journey of several months, a human crew will not be at its best physically and more vulnerable to potential exposure while largely on its own.

Multi-stakeholder participation and international cooperation and harmonization are thus necessary. It is imperative that the regulatory gap in international law, which at present leaves the obligation for the private sector to comply with the United States Outer Space Treaty (OST) in limbo, is closed. The OST requires state parties to authorize and continually supervise non-governmental entities, including private sector enterprises, that perform any space-related activity¹¹. However, the legislation that would grant jurisdiction to the appropriate national regulatory agencies is missing worldwide. As a result, governments cannot currently control or supervise space activities and planetary protection issues resulting from private endeavours¹². Sufficient evidence of this was the privately funded Israeli SpaceIL Beresheet, which hard-landed on the Moon in 2019, carrying an undisclosed cargo of biological materials¹³.

Identifying existing issues with the human exploration of Mars will help to create a path forwards, including: (i) action from the scientific community to establish clear planetary protection protocols for human missions to Mars, (ii) development of international laws and policies covering all spacefaring nations and their private partners, and (iii) a commitment from all stakeholders, with a clear understanding of the legal repercussions for deliberate or inadvertent transgressions. The astrobiology community, Planetary Protection, space agencies and their private partners will need to work together and support each other towards such a ‘new deal’, which should enable critical astrobiological goals to be advanced while supporting preparation for safer human exploration.

The private sector needs to be fully integrated in the process. Only a minimal fraction of private space investments in crewed flights would be needed to generate ambitious and focused programmes for the search for extant life on Mars in the next two decades. Such programmes would provide critical data to help in the design of in situ planetary protection experiments: how to make the residence of a human crew safer, and how to support the efforts of policy makers with data to help them develop optimized protocols, rules, and regulations that engage private partners from the start. These policy makers would need to issue clear guidelines for human exploration by profoundly reworking the first and only OST¹¹, most reasonably through the United Nations Office for Outer Space Affairs (UNOOSA), and including in the process scientists drawn from the astrobiology community.

There could be no stronger combination of intellectual and material assets than a teaming between the international astrobiology community, with national space agencies, private companies, Planetary Protection offices and policy makers engaging in dialogue with the aim of designing robotic precursor missions where clear milestones and deadlines are established by, and for, all stakeholders. And, critically, this should be done before the crewed space race to Mars begins. We are at a tipping point: we can still make a decision that will define how we approach our first steps as an interplanetary civilization in an alien environment, and here we have described the pathway that allows us to do so responsibly, ethically and for the benefit of all involved.