Are we likely to find extraterrestrial life? Do we have a plan if we do? My answers to these questions are yes and no, respectively.

From spacecraft observations we can certainly rule out any widespread life or intelligent life on the other worlds of our Solar System. However, there very well may be microbial life dormant or below the surface on Mars, Europa (a moon of Jupiter), or Enceladus (a moon of Saturn). There are four reasons to be optimistic that life will be found on other worlds. First, life is composed of elements such as carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur, which are common in the universe. Second, all life on Earth requires liquid water to grow or reproduce, and we have clear evidence that such water has existed on Mars in the past (and that there is currently liquid water below the ice on Europa and Enceladus). Third, the organic molecules of life such as amino acids can be produced easily in non-biological processes, and organic molecules are found in many places in the outer Solar System. Finally, life appeared quite early in Earth’s history, soon after the surface cooled enough for liquid water to be present. All this bodes well for the search for life beyond the Earth, and so we search.

What we search for is not just life, but convincing evidence of a second genesis of life—in other words, a different form of life. We now realize that all known life on Earth is part of a single genetic and biochemical system descendant from a common ancestor. If we find evidence of life on another world we will want to compare its genetic and biochemical composition to that of life on Earth and determine if that life is different, implying an independent and separate origin. To make this comparison, we need biologically intact material–either dead or alive. Fossils are not enough for this test.

However, we are not really ethically prepared to take on our search for a second genesis of life. What do we do once we find it? There are three possibilities: we remove it, we ignore it, or we help it.

Some have argued that if we discover a second genesis of life on Mars, we can simply remove it, put it in storage in the laboratory and then continue undeterred with the expansion of Earth life and humans on Mars. Others have argued for a non-interference principle: if we discover a second genesis of life on Mars, we quarantine the planet. I don’t accept either of these points of view. I argue that if we discover a second genesis of life on Mars, we ought to take active steps to enhance that life and alter Mars so as to allow that life to thrive.

Proposing to help Martian life assumes that we can know that it needs help. I think it is safe to make that assumption based on the fact that any life on Mars would not exercise dominant control of the cycles of light elements such as nitrogen and carbon, as life on Earth does. Perhaps life on Mars did have such control in the past. Regardless, we should determine what Martian life needs and what environment suits it and then alter Mars so that this indigenous life can globally thrive – dominating the cycles of the light elements.

Contamination from Earth poses a serious problem for restoration ecology on Mars. If Mars were altered to allow for life to spread, any contamination from Earth would also spread and possibly compete with the Martian life. We could not be certain of the outcome. For this reason, we would need to remove all viable Earth life from Mars before the restoration of habitable conditions could commence.

We know that there are viable Earth microorganisms on Mars because all spacecraft to Mars launched after the Viking missions in 1976 were not sterilized. The international committee that sets policy determined that the conditions on Mars were such that no organisms from Earth could grow or reproduce. Thus, sterilization was no longer required. The Pathfinder lander, the two Mars Exploration Rovers, the Beagle 2 lander, and the Phoenix lander each carried about 100,000 viable microorganisms to Mars. None of these contaminants can grow or reproduce on Mars, and any exposed to the Martian sunlight are rapidly destroyed by the biocidal solar ultraviolet light. However microbes left inside the vehicles and shielded from the ultraviolet light would remain dormant yet viable. But if conditions on Mars were altered (by human or natural means) so that water once again flowed on the surface, this terrestrial contamination would wash out and could begin to grow. In these instances, we would have to remove all Earth contaminants to let Mars’ life develop isolated. It is essential that all future exploration of Mars be designed to be biologically reversible, where any interference or contaminants from Earth can be removed. This preserves our options in the event we discover what we’re searching for: a second genesis of life.

A few years ago, I wrote the following: “All I really need to know I learned from ‘Star Trek’—to seek out new civilizations, to keep my phaser set on stun, and never to put all the officers in one shuttlecraft.” But now, as the possibilities of commercial space travel, space colonization and discovering a second genesis of life become realities, I think that we need something more—a deep consideration of what it would mean to discover “new civilizations” populated by extraterrestrial others. What would it mean to discover life as we don’t know it? How should we relate to unearthly environments and new life forms? In other words, what would it mean for us to take seriously a duty of cosmic concern?

Although unquenched curiosity and a deep desire to understand the universe around us are primary motivators for going where no one has gone before, there are increasing appeals to the necessity of leaving our earthly home in order to survive. A decade ago, astrophysicist Stephen Hawking warned us,

“I don’t think that the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I’m an optimist. We will reach out to the stars.”

A more likely destination than the stars would be to our neighbor planet Mars. It seems possible that we could “terraform” Mars—that is, transform it into a new Earth using University of Wisconsin botanist James Graham’s recipe: a large dose of heat and a smattering of bacteria, lichens and, eventually, redwoods. This is an intriguing possibility for some and a horrifying thought for others.

Perhaps a more fascinating possibility is that we will unearth—actually, “unmars”—microbial life below the surface of the red planet. Then what do we do? Observe it? Collect it? Study it? Send it back to earth?

Before succumbing to Hawking’s appeal to get off of our gradually decaying terrestrial home and spread into space, we would do well to recognize that our track record here on earth is suspect regarding how we treat one another and the environment. Indeed, it is increasingly hard to deny our own culpability in unchecked pollution and the warming of planet earth. How can we be trusted in developing a new celestial environment when we hardly understand how to sustainably care for our own?

As we venture far from terra firma, we could use a good dose of humility. If we go where no one has gone before, there are likely to be unintended consequences. We need to be conscious and humble primarily because we don’t know what we don’t know. Further, the impact of the decisions we make and the actions we take today will affect not only—perhaps not even primarily—us but also future generations of humans and—assuming that Earth may be only one of many environments where life can emerge—novel forms of extraterrestrial life.

We should ask not what we can gain from the cosmos, but what we can do to understand and care for the cosmos. The answer does not lie solely in cultivating Martian life to the best of our ability. This decision can only be made through negotiating bioethical concerns. Let me suggest the following guidelines for exercising cosmic concern:

1. Cosmos preservation insists that we value other worlds and life forms for their own sake, apart from our curiosity, interest, or profit.

2. Cosmos conservation mandates care for the universe’s resources, environments, and life forms, including consideration of our impact on extraterrestrial life and evolution.

3. Cosmos sustainability cautions us to refrain from irreversible harm, raising the question of what would constitute “harm” to Mars and other celestial bodies and to life as we don’t know it. At a minimum, we must guard against “forward contamination,” the introduction of terrestrial microbes to other worlds, and “backward contamination,” bringing extraterrestrial microbes back home.

4. Cosmos stewardship holds us accountable for our actions, compelling us to consider how our actions affect others—both human and not— including how we affect our vast surroundings and the future. From research in subatomic space, we have learned that mere observation can change the characteristics of what is observed. Are we obligated to leave certain areas of the cosmos unseen, uninvestigated, or untouched by human hands or rover probes?

5. Respect for the extraterrestrial other invites a deep concern for the intrinsic value of the cosmos and the life within it, not only “charismatic fauna” such as extraterrestrial life but also microbes and non–carbon-based life.

There is much about the cosmos that we do not know, and so we explore. But we ought not go unreflectively where no one has gone before. These guidelines can prevent exploration from turning into exploitation and should inform our journeys before we take steps into the final frontier.