The concept of terraforming Mars — transforming the planet's climate to support life as we know it — has long belonged to the realm of science fiction. But a new study argues that it's time to take the idea seriously.

"Thirty years ago, terraforming Mars wasn't just hard — it was impossible," said Erika DeBenedictis, CEO of Pioneer Labs and lead author of the new paper. "But new technology like [SpaceX's] Starship and synthetic biology have now made it a real possibility."

The paper debates the complex ethical questions that must be considered if we're to terraform Mars and lays the blueprint for a potential path forward.

"Advocates argue that more life is better than less, and terraforming Mars could mark humanity's first act of planetary stewardship with a net positive environmental impact," said DeBenedictis.

Why terraform Mars?
Put succinctly, "living planets are better than dead ones," said study co-author Edwin Kite, an associate professor at the University of Chicago. "We now know that Mars was habitable in the past, from data returned by the Mars rovers, so greening Mars could be viewed as the ultimate environmental restoration challenge."

Though full terraforming may take centuries, if not millennia, the long-term goal would be a Mars with stable liquid water, breathable oxygen and a thriving ecosystem. In the short term, this might mean only small patches of microbial life; in the distant future, there could perhaps be human cities on the planet.

And if we reach the scale of cities, perhaps that's a stepping stone to even more significant exploration for our species. "As we move out into the galaxy, we will need base camps, and a base camp on the scale of the galaxy is a habitable planet," said Kite.

For co-author Robin Wordsworth, a professor of environmental and planetary science at Harvard, the argument for terraforming Mars goes beyond human colonization to the propagation of life in general.

"I see humanity as part of the biosphere, not separate from it," he said. "Life is precious — we know of nowhere else in the universe where it exists — and we have a duty to conserve it on Earth, but also to consider how we could begin to propagate it to other worlds."

What about Earth?
It's not all about looking beyond the bounds of Earth; terraforming Mars could also help us solve climate and sustainability challenges at home, advocates say.

Nina Lanza, a planetary scientist at Los Alamos National Laboratory and a co-author on the paper, sees Mars as a prime testbed for planetary engineering.

"If we want to learn how to modify our environment here on Earth, to keep it in a configuration that suits us and other life forms, maybe it would be better to experiment on Mars and say, 'Look, does this work?'" she said. "I personally would like to be a little more conservative with our home planet. This is the only place we can live."

There are technological lessons to be learned, too.

"Concretely, developing and adopting green technology on Earth often falters because it must compete with dirtier alternatives that benefit from decades of infrastructure investment and entrenched interests," said DeBenedictis. "Mars is a unique target market because it has no oil, no existing infrastructure and no status quo. For this reason, developing green technologies for space is a powerful strategy for maturing it for use on Earth."

Why not terraform Mars?
But we should take a few lessons from "Jurassic Park" when thinking about terraforming, some scientists say: Before asking, "Could we?" we need to ask, "Should we?"

"If we decide to terraform Mars, then we will really change it in ways that may or may not be reversible," said Lanza. "Mars is its own planet and has its own history. When we terraform, then we effectively don't have the opportunity to study that anymore, and we may lose knowledge about how planets form and evolve."

Most dramatically, we may destroy potential evidence of ancient Martian life, if such evidence exists.

"If we modify the environment on Mars, we're going to change the chemistry of the surface and of the subsurface, eventually," said Lanza, pointing out that such actions might erase any traces of life on Mars. "I can't say for certain. It's very complicated, but it's a risk."

How to terraform Mars
Terraforming Mars would require massive changes, namely the warming of the planet to support both oxygen-producing microbes and liquid water. While all the technologies to terraform Mars are not yet available, the authors of the paper propose three phases of development.

First, scientists would use abiotic climate engineering techniques — such as deploying reflective solar sails, dispersing nanoparticles, or laying aerogel tiles — to warm the surface by at least 30 degrees Celsius (86 degrees Fahrenheit), enough to melt subsurface ice and release trapped carbon dioxide. This warming would thicken the Martian atmosphere and potentially support the presence of stable liquid water.

The second phase would introduce extremophile microbes — likely anaerobic and genetically engineered ones — capable of surviving in Mars' harsh conditions and kickstarting ecological succession. These organisms would begin producing oxygen and organic matter, slowly altering planetary chemistry.

The third and longest phase would focus on building a complex biosphere, increasing atmospheric pressure and oxygen content to eventually support more advanced plant life, and, in the very long term, potentially allow humans to breathe unassisted.