Chris Carberry is CEO of Explore Mars, Inc. and author of “Alcohol in Space.” Rick Zucker is Explore Mars’ vice president for policy.

Planetary protection may sound like something from the realm of science fiction or like the precautions taken to avert an alien invasion of Earth. In fact, from a certain perspective, the latter is the better analogy. 

According to NASA, planetary protection is “the practice of protecting solar system bodies from contamination by Earth life and protecting Earth from possible life forms that may be returned from other solar system bodies.” 

However, the “possible life forms” referred to are almost certainly microbial, not intelligent life. NASA even employs an individual with the impressive title of Planetary Protection Officer, responsible for assuring that precautions are taken not only to prevent Earth from being contaminated by alien microbes (known as “backward contamination”) but also to manage the exposure to other planetary bodies from Earth microbes (“forward contamination”).

While it is not a well-known topic outside space exploration circles, planetary protection is not a new area of study and concern. For many decades, it has been a topic for space conferences, workshops, academic papers, etc., but until recently, it was rarely considered an urgent matter. After all, humanity was far from returning to the Moon, going on to Mars, or even developing a viable plan to achieve such a goal.

This is no longer the case.

Government, commercial, and international human spaceflight plans are accelerating. Humanity is poised to return to the Moon during the present decade and land humans on Mars in the 2030s. For the first time in history, private entities are also planning viable missions to land vehicles on the lunar and Martian surfaces. Reality is swiftly catching up with our dreams, but planetary protection policy is not moving forward at the same pace. This could hinder human spaceflight plans (government and commercial) over the next couple of decades unless modifications and standards are agreed to and acted upon by all. 

Under existing policies, no human mission would be allowed to venture to the surface of Mars. NASA allows no more than 300,000 spores (single-celled organisms) to accompany robotic missions that land on Mars. Human bodies, in comparison, contain trillions of microorganisms. It will be impossible for human missions to achieve the same level of microbial cleanliness achieved for robotic landers. 

What can be done to take reasonable planetary protection precautions, but also enable a human presence on Mars and other interplanetary destinations? Several years ago, NASA began to address this question. In 2018, the NASA Advisory Council, at the behest of its Regulatory and Policy Committee, recommended that NASA review its planetary protection policies, stating that the current rules, based on guidelines issued by the Committee for Space Research (COSPAR), would exclude the prospect of human exploration (specifically Mars) and some potential commercial activities. 

In response, NASA issued two Interim Directives regarding planetary protection policy for the Moon and Mars. The lunar directive lowered the contamination risk level of the Moon. Except for lunar Arctic regions and Apollo landing sites, no planetary protection requirements would be needed for human missions to the Moon since it is entirely exposed to the vacuum of space. 

As for Mars, the directive stated that “NASA will develop risk-informed decision-making implementation strategies for human missions to Mars, which account for and balance the needs of human space exploration, science, commercial activities, and safety.” While NASA has issued additional planetary protection policies since then, protocols for a human presence on Mars are still not clearly defined.

Appropriate precautions to prevent the needless contamination of Mars and other planetary bodies (as well as Earth) should certainly be taken, but this must be accomplished sensibly. Protocols need to be developed with the assumption that a human presence on Mars will begin no later than the 2030s and that human explorers will need to gain access to regions on Mars that are both scientifically interesting and have potential access to in-situ resources. Specifically, this means locations with potential access to water. This concern is articulated in the report of the Ninth Community Workshop for Achievability and Sustainability of Mars (AM IX) (Affording Mars | Explore Mars) which states:

 “A well-crafted policy should be agreed to well before humans step foot on Mars. Such agreement must entail a sensible balance between the prevention of forward and backward contamination vs. maximizing the value of scientists on the surface of Mars. It should be noted that a human astrobiologist on the surface of Mars would be of great value not only to determine the existence of past or present life, but also to oversee planetary protection protocols.”

This could include setting up safe zones for human activities and special regions where only robotic exploration is allowed, similar to policies utilized in Antarctica.

A well-balanced planetary protection policy that not only allows a human presence on Mars beginning in the 2030s but also takes reasonable precautions to minimize microbial contamination of Mars needs to be established soon. Moreover, actions should be taken to ensure that all nations abide by planetary protection policies or, at the very least, publicize that some nations are failing to comply with international policies. If these actions are taken, we will be far more likely to answer the age-old question: Is there – or has there ever been – indigenous life on Mars?

The question of planetary protection will be discussed at the upcoming Humans to Mars Summit taking place on May 16-18, 2023, at the National Academy of Sciences Building in Washington.