Ask Ethan: What right do we have to colonize other worlds?

Back in ancient times, we knew that there were five wanderers — or planets — that moved through the night sky: Mercury, Venus, Mars, Jupiter, and Saturn, in addition to the Moon and the stars. For generations, humans invented stories about the types of aliens that might be living on those worlds, and speculated wildly about what kinds of life forms might exist on worlds that orbited around other stars far beyond our own Solar System. Today, we know of more planets and many more moons within our Solar System, and are closing in on 6000 confirmed exoplanets around stars elsewhere in the Milky Way. All told, there are expected to be hundreds of billions or even trillions of planets within our galaxy, but none are yet known to harbor any form of life at all.

As humans, our dreams of space exploration are often accompanied by another dream: that of space colonization. Could we extend humanity’s presence to worlds other than our own? And if we can, should we? And if so, how should we do it in an ethical fashion? That’s the question of Anniece Isler, who was talking with her daughter and the following topic came up:

“I have been talking to my daughter about Artemis. She asked me what right did we have to establish a community on the Moon. I compared our exploration to Columbus. As I think about it more, why is it, with more than a million planets and stars in the galaxy, we treat our exploration like we are the only living creatures?”

There’s a lot to unpack here: from the Moon to space law to the rest of the Solar System and galaxy, including many ethical issues, while simultaneously being supremely limited by our ignorance at present. Let’s begin there.

The MeerKAT array, the first step in the construction of the Square Kilometer Array, has already produced an unprecedented set of science images and data that takes us one step closer toward understanding our galactic center. The science of SETI and the science of astronomy and astrophysics have many overlaps as we seek to uncover all that’s out there in the Universe.

Since the birth of SETI more than 60 years ago, humanity has actively been searching for signs of life elsewhere in the Universe. We’ve imaged the surfaces and even landed on a large number of planets and moons within our Solar System, probing those worlds for surefire signatures of life and biological activity — either present or past — for nearly as long. And in the modern age, we’ve begun measuring the atmospheric contents of rocky planets found orbiting around other stars, looking for the telltale biochemical signatures that would reveal the presence of life on any of those worlds.

So far, as much as we might have hoped for a positive detection, all we have are spurious claims of positive detections and unconfirmed assertions that life must exist there. From a scientific perspective, we still have no evidence that there’s life anywhere else other than here. That doesn’t mean that there is (or was) no life elsewhere in the Solar System, the galaxy, or the Universe, but it does teach us that life is not so exceedingly common that it exists on every world that’s out there.

It’s a bit like imagining you woke up tomorrow, alive and unharmed, but there was no sign of anyone else anywhere you looked. You might wonder to yourself, “Am I the only surviving human on Earth?” You wouldn’t know right away, and so you’d expand your search radius in seeking another: looking in your house, then in your city, then your state, then even your entire country. As soon as you found a second human — your first human other than you — you would conclude that you weren’t alone, and if there were at least two survivors, there are likely others. But so long as you’re the only one you know of, you can’t rule out the horrifying possibility that you truly are alone.

The surfaces of six different worlds in our Solar System, from an asteroid to the Moon to Venus, Mars, Titan, and Earth, showcase a wide diversity of properties and histories. While only Earth is known to contain liquid water rainfall and large cumulations of liquid water on its surface, other worlds have other forms of precipitation and surface liquids, both at present and also in the distant past. Perhaps, long ago, Earth was joined by other worlds or even other planets, such as Mars and Venus, in possessing liquid water and perhaps life on its planetary surface.

This is where the search for alien life currently is at present. We know there are tremendous numbers of worlds in our Solar System, many of which are excellent candidates for harboring at least some form of life. Venus, Mars, Titan, Europa, Enceladus, Triton, Pluto, Ganymede, Eris, and more have all been suggested as worlds that could house life, past or present, either in their atmospheres, on their surfaces, or in subterranean/undersea locations. We know that there are hundreds of billions of stars within the Milky Way, many of which are composed of similar chemical ingredients to what we find in our own Solar System, with most of them expected to house rich planetary systems just like our own home.

But when it comes to life, we only have Earth as our lone example of a positive detection. Despite all of the possibilities that are out there, we don’t know:

• how many of those worlds ever had life arise on them,
• how many of those worlds had life persist and thrive on them for long periods of time,
• how many of those worlds have life on them, and therefore are inhabited, at present,
• how many of those worlds have seen that life evolve into complex and differentiated life forms,
• and how many of those worlds have had life become intelligent and technologically advanced, like we fancy ourselves to be as humans here on Earth.

There may be a grand cosmic lottery out there, where every world around every star in our galaxy is a lottery ticket, just like Earth is. While we know we won some sort of prize in the cosmic lottery, we have no idea of what the other prizes are, whether we’re the grand prize or not, and what the odds are of winning any prize at all. We can, and perhaps should, assume that “if it can happen here, it almost certainly has happened elsewhere,” but until we find a second example of an inhabited world, we cannot draw any firm conclusions.

With recent discoveries, we have a tremendous amount of knowledge about the number of planets out there, including what stars they’re around and what sizes and distances from their star they possess. But when it comes to the question of whether they’re inhabited, we have no information at all.

However, we can’t simply assume that a world that isn’t overflowing with life — the way, for example, that Earth is — either has no life on it, anywhere, or has never had life on it. Venus may have once been a very life-rich world, and it’s possible that life still persists somewhere in the Venusian atmosphere. Mars is a world that once had a significant amount of liquid water on its surface, including oceans, lakes, and rivers: features that persisted for more than a billion years. It’s possible that some extreme organisms may still exist beneath the Martian surface, and it’s eminently possible that evidence of past microbial life still remains buried in Mars’s geological history. Titan has liquid methane lakes on its surface; many other large moons and Kuiper belt objects have icy surfaces with liquid water oceans beneath them. The possibilities for simple life, even here in our own Solar System, are copious.

It’s for this reason, primarily, that scientists have long been taking extreme caution not to pollute any of these worlds with organisms that originated here on Earth. If one of our goals is to determine how prevalent life truly is in the Universe, including here in our Solar System, we have to ensure that we’re not polluting those worlds with terrestrial life forms before we’ve determined what sort of life either is there at present or was there previously. While there are certainly many explorers who have the same spirit as Columbus — where they view any foreign life they’ll encounter as expendable impediments to colonization and the furthering of their own ambitions — most of us view that as a supremely unethical attitude today. At the very least, we should inform ourselves about what else is out there, native to other worlds, before we wantonly destroy it to serve our own ends.

Apollo 11 brought humans onto the surface of the Moon for the first time in 1969. Shown here is Buzz Aldrin setting up the Solar Wind experiment as part of Apollo 11, with Neil Armstrong snapping the photograph.

Our very first steps off of our home world, as human beings originating from Earth, have taken us to our closest companion world: the Moon. For a brief few years in the late 1960s and early 1970s, a total of 12 human beings set foot on the lunar surface. Initially, returning astronauts were quarantined: a (perhaps overly cautious) precaution against any foreign pathogens they may have picked up while on the Moon. Today, we understand that the Moon is extremely unlikely to have ever harbored any forms of life at all, much less any forms of life that could be infectious and harmful to living creatures of terrestrial origin. Although life may yet be plentiful — in the Universe, around other stars in the galaxy, or even on other worlds right here in the Solar System — the Moon remains a long-shot candidate for biological activity.

On the other hand, the Moon is by far the closest world to Earth. It ranges in distance from Earth from around 356,000 km to 407,000 km, whereas the next-closest worlds, even at closest approach, are tens of millions of kilometers away. Conventional rockets would take several months, at minimum, to reach any other world in the Solar System, but a one-way journey from the Earth to the Moon (or back) takes a mere three days. The Moon’s close proximity, its distance from the Sun (the same, roughly, as Earth’s), its large physical size, and its (very likely) uninhabited nature make it an excellent candidate world for exploration, congruent with the aims of NASA’s Artemis.

The launch of NASA’s Space Launch System (SLS) rocket, carrying the Orion spacecraft, occurred on November 16, 2022. The Artemis mission is planned to bring humans to the Moon for the first time since the end of the Apollo program a half-century ago.

Those same factors make it a very interesting and compelling candidate world for colonization and potential terraforming, or establishing a long-term human presence there, as well. Although there are precious few laws and regulations governing human activity in space — with the most notable one being the Outer Space Treaty — there are a few that very much apply to any humans seeking to establish a colony on the Moon.

• You cannot conduct an act of war or aggression, including the destruction of property, against any nation (or property of that nation) in space or on another world.
• You cannot establish ownership of another world or any part of it, although you are allowed to settle there.
• You cannot form a new nation or set up a new government on another world or any part of it.
• And you cannot declare sovereignty on another world; you are still bound by the rules and laws of your home nation (and home planet) back on Earth.

Although a few prominent, very wealthy public figures have attacked these regulations and have even gone so far as to announce their intention to flout them, they remain intact today.

It makes sense, at least on the surface, that many humans would look off-world as the next frontier: most of the inhabitable land (and even some of the questionably inhabitable sections of land, ice, and water) here on Earth has already been colonized by humans in some form. Our population, as a species, has already crossed the 8 billion threshold and continues to rise even today: representing more than quadruple the number of humans that lived on Earth in the year 1900. On the other hand, there are no humans on any worlds other than Earth, and only a handful of humans in space at any given time, making those environments a natural location to consider when it comes to expanding humanity’s presence.

While terraforming an entire world, like the Moon, may be a monumental task, a smaller, more easily reachable goal would be to create a series of airtight and watertight domes that could be built and inhabited individually. This pathway toward terraforming could be done a little bit at a time, enabling us to build up our way to an inhabited, colonized world.

Of course, considering colonizing a world like the Moon poses many difficulties. Humans, from a health perspective, fare very poorly in space and in severely low-gravity environments. Our bone densities drop, we experience space blindness, our muscle mass (and sexual functioning) decreases, etc. We also miss the protection of our atmosphere and magnetic field, as cosmic rays and solar radiation pose a significantly increased threat to our long-term health. Additionally, there is no infrastructure, no readily-available sources of food and drinking water, and no medical care available in space. Although we can imagine a future where we’ve constructed that infrastructure and made those resources readily available on other worlds, there are a lot of scientific and technological steps that will need to be achieved before that comes to fruition.

Compared to the Moon, however, there’s arguably a better candidate for establishing a long-term human presence right here in our proverbial backyard: Mars. Mars isn’t just larger, more massive, and more distant, from Earth (the last of which is not an advantage), but:

• has large amounts of frozen water and precipitation right on its surface,
• possesses an atmosphere that allows for the persistence of salt-rich liquid water at some locations on its surface,
• offers some (but not as much as Earth) protection against radiation and cosmic rays,
• and has an Earth-like rotational period of 24 hours and 37 minutes, as compared to the ~27 day period of the Moon.

Whereas the Moon’s surface gravity is only about one-sixth of what the surface gravity on Earth, Mars’s is about double that of the Moon: not quite Earth-like, but a whole lot better than the Moon for human bodies.

Although Earth and Venus are the two largest rocky objects in the Solar System, Mars, Mercury, as well as over 100 of the largest moons, asteroids, and Kuiper belt objects have all achieved hydrostatic equilibrium. Although our Moon is the fifth largest moon in the Solar System, its surface gravity is only about half of the surface gravity on Mars.

Back in the early 1970s, NASA landed a spacecraft on the surface of Mars for the first time: the Viking landers. (They’ve since been joined by many other landers and several generations of rovers, to say nothing of the many orbiters that accompany and complement them.) On board the Viking mission were a few apparatuses and instruments that intended to search for signs of organic material. This doesn’t necessarily imply life, but simply what we call organics: molecules that contain carbon atoms as well as carbon-hydrogen bonds. DNA is an example of an organic molecule, but so are methane and hydrogen cyanide; many organic molecules are most commonly produced by chemical, not biological, processes.

All of the “tests for life” that were performed came back negative, save one. An instrument that was designed to:

• take scooped Martian soil,
• heat and combust it,
• and look for signatures that show the presence of organic material,

came back positive. Does this mean that there is, or at some point was, life on Mars? Possibly, but not necessarily. Subsequent scooping and combustion tests yielded null results; follow-up missions also yielded null results. Was it a fluke? Was it a “lucky” and rare location (and scoop) that picked up actual Martian life? Was it the result of terrestrial life that stowed away inside the instrument, and mimicked the signs we’d expect to find if there was native life on Mars? These questions are still debated today, and raise a slew of ethical questions that we’re compelled to reckon with.

The first truly successful landers, Viking 1 and 2, returned data and images for years, including providing a controversial signal that may have indicated life’s presence on the red planet. Decades later, we still don’t have the confirmation to know whether that one successful test was a false positive or not, but the bouldery terrain remains a mystery.

The main issue is this: if we “move fast and break things” when it comes to space colonization, we’re very likely to run into two major pitfalls.

1. We’re very likely to contaminate an otherwise pristine environment with life forms originating from modern-day Earth. Once an environment is contaminated in that fashion, it may become impossible to detect the presence of any current or ancient (i.e., now-extinct) life that was native to another world. Through just one rash action, we could forever lose the ability to know what was present on that world, as far as life is concerned, before our arrival.
2. If there is any life on that world that’s native to that world, we have no idea what it will do to either human beings once it comes into contact with us, or what it will do to the microbes we bring with us (including the ones that live symbiotically on and within us). It’s possible that native life from another world is toxic, pathogenic, or even lethal to humans, and it’s also possible that the combination of those life forms with terrestrial ones will pose an even greater danger.

Again, our ignorance is so great — and there are so many who value both fundamental knowledge and the personal safety of themselves and others so cheaply — that I frequently fear that it will be the most reckless among us, rather than those among us who carefully consider and scrupulously reckon with these issues, who will ultimately be the first to engage in genuine colonization efforts.

This aerial view of Grand Prismatic Spring in Yellowstone National Park is one of the most iconic hydrothermal features on land in the world. The colors are due to the various organisms living under these extreme conditions, and depend on the amount of sunlight that reaches the various parts of the springs. Hydrothermal fields like this are some of the best candidate locations for life to have first arisen on a young Earth, and similar features may be home to abundant life on a variety of exoplanets.

All of which is to say, Anniece, that I think your daughter is on the right track. Imagine how different the history of our own planet would have been if long ago — a million years ago, 100 million years ago, a billion years ago or more — an intelligent alien species came to Earth with the intent of colonizing it. Would the alien life that arrived have outcompeted the life forms that originated here, driving Earth-native life to extinction? Would it have interbred with terrestrial life, forever altering our evolutionary pathways? Would the aliens, upon encountering Earth life, discover that it was toxic, poisonous, infectious, or otherwise deadly to them?

It makes me think of the importance of what the Star Trek universe would call “the prime directive,” which is not to interfere with or meddle in the affairs of alien civilizations in particular and of alien life forms in general. We have long passed the age of imperialism; we recognize that colonizing, plundering, and exploiting the resources of an already-inhabited land is an affront to the sovereignty and self-determination of all forms of life that are already in place there. And yet, it chills me to think about the fact that we have not yet figured out how to mitigate humanity’s own worst impulses when it comes to desiring a resource that we do not ourselves possess: many of us will simply take it, even today, by force. It’s wrong and unsustainable on modern-day Earth, and it will be no different in space. Although we have no right to colonize other worlds, including other worlds that may already be inhabited, I have no idea how to effectively stop those with the resources to do so from recklessly and unilaterally doing it.

Send in your Ask Ethan questions to startswithabang at gmail dot com!