A field of alien plants growing on an imagined exoplanet

Over millions of years and under the right conditions, tiny microbes sent to a foreign exoplanet could evolve to form an alien landscape like the one in this artist’s impression.

Melkor3D/Shutterstock

Q&A: Should we seed life on alien worlds?

Astronomers have detected more than 3000 planets beyond our solar system, and just a couple weeks ago they discovered an Earth-like planet in the solar system next door. Most—if not all—of these worlds are unlikely to harbor life, but what if we put it there?

In an essay published last month in Astrophysics and Space Science, theoretical physicist Claudius Gros of Goethe University Frankfurt in Germany suggests we do just that. His proposed Genesis Project would send artificially intelligent probes to lifeless worlds to seed them with microbes. Over millions of years, they might evolve into multicellular organisms, and, perhaps eventually, plants and animals. In an interview with Science, Gros talked artificial intelligence (AI), searching for habitable planets, and what kind of organisms he’d like to see evolve. This interview has been edited for brevity and clarity.

Claudius Gros

Claudius Gros

Courtesy of Dr. Claudius Gros

Q: What inspired you to dream up the Genesis Project?

A: Much of it was science fiction. When I was younger, I read 2001: a Space Odyssey. I didn’t understand a whole lot of it, but I was very interested in life and the cosmos. I still watch things like Stargate and Avatar and it makes me wonder what kind of life exists, or could exist, on other planets.

Q: What would the starting microbes look like?

A: There are two strategies: AI could create specifically adapted microbes for each planet’s conditions, like a very hot planet would be given bacteria called extremophiles that are known to survive in very high temperatures. Or, the AI could just send down the same kind of microbes on many planets. The first would have better survivability, but the second would have more opportunities to branch off and create different species—though many would perish in harsher climates. In the end, you would want to optimize for the ability to evolve but still make sure they wouldn’t all die right away—so probably a combination of those two options. But finding how to optimize the ability to evolve is something we’d have to figure out.

Q: How would AI facilitate the process?

A: AI is important because we will not be around to direct anything once the probes arrive at a planet. The robots will have to decide if a certain planet should receive microbes and the chance to evolve life. The AI would be aboard the Genesis probe, which would only be about the size of a smartphone. And the probe would be sent to an exoplanet using solar sails to accelerate, similar to the Breakthrough Starshot mission, which plans to send probes to Alpha Centauri in search of life. Once the probe arrives, it would fall into orbit around the planet and, after double checking the planet was lifeless, begin the seeding process. Microbes would be inside small capsules, only millimeters long, and shot down to the exoplanet’s surface. The capsule would crash land, but the AI would be able to calculate an angle to shoot them at so the landing wouldn’t be lethal.

First, the AI would seed with photosynthesizing microbes. These would make oxygen accumulate in the atmosphere so that other kinds of life, like animals, could live there. When oxygen levels were high enough, which the probe would measure from orbit, eukaryotic microbes—which have more specialized cell machinery and make up multicellular life—would be sent down, too. Then, the probe would stop. That is where evolution would begin on a planet, and over millions of years, there might be many kinds of alien plants and animals.

Q: What happens if life is already there?

A: That is very important. We’d try to avoid that, we want to target only planets where there is no life. So AI would scout for uninhabited planets from orbit to make sure there was no life there. The probe could spot larger, more complex organisms pretty easily, but smaller organisms might also be detected with technology that already exists called spectrometry. This technique is how we saw that there might be water on Mars. A spectrometer could analyze light from a planet’s surface to determine what kind of atoms are there because each kind of atom has a different signal. It wouldn’t be perfect, but if there were no obvious signs of life—like large amounts of oxygen or carbon dioxide—the probe would seed the surface with microbes.

Q: What kind of organisms would you like to see evolve from these seeds?

A: The dream would be something intelligent. There is a theory that we became an intelligent species when we began to develop language. So I think that any animal that would evolve to be what is referred to as intelligent life would have to be a social being.

For example, I like to imagine a planet where gravity is more intense. Animals would be heavier then, so perhaps they would evolve with more limbs to spread out their weight more evenly. With more limbs, maybe they would be excellent climbers and live in forest communities. They could even have a type of sign language instead of a vocal language to use the extra limbs to their full potential.

I would also find it fascinating if there would be a moving plant. In my mind, this looks like [a] flat green sheet of paper that crawls like a larva. It wouldn’t move quickly or even a lot, because energy production wouldn’t be massively efficient with photosynthesis. But maybe it would live in the mountains and lay on a rock all day to gather energy, and crawl down to a water source when it got thirsty.

Q: How soon would this kind of project be ready to launch?

A: Optimistically, a Genesis probe could be sent in 50 years. Pessimistically, 100 years. We could build the small probe in a decade or two once we figure out solar sails—which the Starshot mission is already doing—but the real challenges would be to program the [AI], and also be able to gather more data about the exoplanets we would send the probe to. It would be a waste if we sent a probe to a planet that was completely uninhabitable, like planets in extreme temperature zones or that are not tectonically active. If a planet isn’t tectonically active, that means it has no volcanoes and can’t produce carbon dioxide, and that’s a really important building block to have when trying to seed life.

Q: Because of the time it takes to travel to other worlds and for life to evolve, we’d never be able to see the products of the Genesis Project. So why do it?

A: Personally, I think life is beautiful. We should give it chance to flourish, even if we never see the result. But for those who think we need to do interstellar projects for human benefit, Genesis is the only one that let’s humans play an active part in the cosmos. It is a question of if humans really want to change part of our cosmos actively, or do we want to just observe passively? The Genesis Project gives humans a chance to leave a legacy.