If humans want to establish a long-term colony on Mars or elsewhere in space, we'll eventually need to be able to have children there.

But reproducing in the vastly different Martian environment would be extremely complicated.

All of the health effects people experience in space — exposure to radiation and changes in bone, muscle, and bodily fluids — would have effects on a developing fetus or young child.

We may someday decide to edit human DNA to give people traits that could help them thrive on Mars.

Eventually, that could lead to creating new species of humans.



This tiny blue rock upon which we hurtle through the vastness of space is the perfect home for us.

We can breathe the air and drink the water — both of which are essential to life as we know it. Our atmosphere protects us from radiation that could mutate our DNA and cut our lives short. We and the other creatures on Earth have evolved to function according to the planet's gravity, which affects our bones, muscles, and the fluids inside our body.

NASA and other space agencies — as well as individuals like Elon Musk — are actively working towards creating settlements on Mars. But before humans can attempt to establish long-term outposts on Mars or elsewhere in space, we have a lot to consider. Beyond the logistics of space travel, food, water, breathable air, and radiation, there's the question of human reproduction.

A paper newly published in the journal Futures describes just how complicated that could be.

Since Mars is the likely first location for a long-term populated outpost, the researchers behind the paper decided to analyze some physical and social problems that we'd encounter in trying to have babies on the red planet.

"A manned mission to Mars and the establishment of the first human settlement in outer space was once a mere figment of science fiction but is now being planned and expected to take place in the following 20 years," the authors wrote. "We assume that human reproduction in a Mars settlement will be necessary for the long-term success of an outer space mission."

Could there ever be new generations of Martians?

Any human settlement on Mars will be initially populated by crews from Earth. But at some point, if we truly want to have a large long-term Martian colony with a sustainable population, kids are going to need to be born there.

Whether or not it's possible to have children in the Martian environment is still unknown.

We know that when astronauts spend time in space, it has serious effects on their bodies. A lack of gravity causes body fluids to shift, which can change and impair vision as pressure changes affect the eyeball. Bones become less dense and muscles can atrophy, though regular exercise can help reduce these effects. People get taller as they stretch out, uncompressed. Then there's radiation exposure, which affects DNA and could increase cancer risk.

The International Space Station (ISS). NASA

Being on Mars wouldn't be exactly like being on the International Space Station, which is where most of this information comes from. But Mars still only has about 38% of the gravity we experience on Earth.

We don't know how these changes would affect reproductive cells, fertilization, embryonic development, the developing fetus, or growing children.

It's possible that children born and raised on Mars might have an easier time adapting to the requirements of life there, since it would be the world they would grow up in. But what those adaptations would look like are anyone's guess.

Many of these questions can be studied, especially with animal models. But they'll be important issues to investigate before any Mars colonization plans take shape.

Ethical questions

Assuming humans do someday try to reproduce in space, a host of other intriguing questions arise.

One is how big a population needs to be to truly sustain itself. According to the paper's authors, accepted estimates of the minimum size for a self-sustaining group range from 5,000 to 5,800 individuals. But they write that a Martian colony may need to have a larger population due to the extreme nature of the environment.

Then there's the issue of reproductive rights. Since living on Mars isn't going to be easy, the authors write that there should be genetic counseling available for couples to make sure that traits that could help people survive on Mars are encouraged in the reproductive process. At the same time, they write that liberalized abortion policies would be important, since pregnancies could pose high risks to mothers and environmental conditions could make serious birth defects more likely.

People who do choose to have children should be carefully supported through that process, according to the paper. That support system would need to extend beyond birth to help parents cope with the stresses that come with Martian children.

The authors also bring up an even bigger question: how much we should use technology to transform humans living in space.

YouTube / SpaceX

Potential solutions

It's possible that some of us carry genetic traits that make us better suited to life on Mars than other people. Such traits may make it easier for our bodies to adapt to reduced gravity, for example, or make us less susceptible to cancer or disability caused by radiation.

A Martian colony might encourage people with those genetic traits to pass them on.

But it also might be possible to use genetic editing technologies to give people these traits and to modify DNA in other ways that make it easier for humans to survive in space. Genetic editing tools like CRISPR, which can find and replace sections of DNA, could allow doctors to modify embryos conceived via in vitro fertilization to give them these space-life-friendly traits.

Eventually, it might turn out that the "humans" who thrive best on Mars don't much resemble people on Earth.

Science fiction authors have wrestled with this idea. In "The Expanse," authors Daniel Abraham and Ty Franck (pen name: James S. A. Corey) describe how "belters," residents of human settlements in the asteroid belt, are different from Earth-born humans. They have elongated bodies uncompressed by gravity, and their bones can't support human weight when exposed to the crushing pressure of life on Earth. It's possible that people born and raised on Mars would have a similarly difficult time adapting to life on Earth.

It's even feasible that humanity might speciate: develop new species that evolve out of Homo sapiens, according to the authors of the paper. They say that's unlikely to happen naturally, but could happen if humans wind up heavily genetically engineered to better survive on different planets.

Is escaping to Mars really a possibility?

In the paper, the authors quote Stephen Hawking, who once said: "I believe that the long-term future of the human race must be space and that it represents an important life insurance for our future survival, as it could prevent the disappearance of humanity by colonizing other planets."

But this paper shows how complicated that insurance policy would be. And that analysis is yet another reminder that we need to ensure that humanity can continue to survive on its home planet.

Astronaut Mae Jemison leads an organization called 100-Year Starship, a NASA- and DARPA-funded project that launched in 2011 to tackle the questions involved in making humans capable of voyaging beyond our solar system within the next 100 years.

But as Jemison explained to me in 2016, most of us are already on the starship that's best suited for carrying us through space: it's Earth.

"We're going to be on this planet," she said.

That's not to say that we shouldn't settle on Mars — it's important to understand how we could survive on new worlds. But we shouldn't avoid tackling simpler issues like climate change in order to keep humanity's first home habitable, too.