Outer space is having a moment. NASA’s Artemis 2 mission is about to take humans farther into space than we have ever gone; SpaceX is preparing to test the latest version of Starship, its interplanetary transport system; and just today, a crew of four astronauts flew to the International Space Station to replace the team that was evacuated last month due to a medical emergency. These efforts are part of a common vision: expanding humanity’s presence beyond Earth, including the eventual creation of human settlements on Mars.
But what would it be like to live on Mars? Aside from the challenges of lower gravity, intense radiation, and toxic soil, an important, but less often considered, factor would be your love life.
People have been traveling to space for more than six decades and have been living off-planet continuously since 2000, when the International Space Station (ISS) became operational. Yet, no one has had sex in space (as far as we know). This is surprising given the extensive research dedicated to understanding nearly every aspect of how space affects biological systems. Not to mention that, as exceptional as they are, astronauts are still human.
It’s not that there hasn’t been an opportunity. In 1992, NASA astronauts Mark Lee and Jan Davis spent 8 days together on the Space Shuttle Endeavour as newlyweds. Lee and Davis kept their marriage a secret until shortly before the launch, but it was still an unusual move for NASA, and despite rampant speculation, no one at the agency would comment after their flight on the possibility of any private interactions the couple may have had while in orbit.
One limitation would certainly have been the lack of privacy aboard the space shuttle. Crew quarters were tiny, making it difficult to join the 250-mile-high club in secret. The ISS is larger but still lacks many truly private or soundproof spaces. Designs for commercial space stations, which could be operational by the end of the decade, could make private orbital interludes more feasible.
Another challenge is the physics of performing what has been called a “human docking maneuver” in microgravity. The basic problem is physics: Any two weightless objects that come into contact will repel one another. Several potential solutions have been developed by starry-eyed inventors, sporting names like the “2-suit” and the “snuggle tunnel.” These solutions incorporate harnesses and velcro; some have even been tested in parabolic flights that provide up to half a minute of microgravity — just long enough for a proof-of-concept quickie.
If we are ever to become a truly multiplanetary species, we will need to not only master the cosmic kama sutra but also its natural consequences. Surprisingly little research in space has focused on reproduction, and the results we do have are largely inconclusive. So far, the only species that has successfully completed the entire reproductive process, from conception to birth, in space is the Japanese rice fish. Studying how fish reproduction is affected by microgravity is convenient because they lay clear eggs, allowing researchers to easily monitor embryo development.
But like most mammals, human babies develop internally, making it much harder to track their growth. In 1980, Soviet researchers sent pregnant rats to space for five days and then returned them to Earth to give birth. Four of the five were successful. The fifth had complications that led to the death of all the pups in her litter. While it wasn’t clear whether the complications were due to the mother’s time in space, exhaustion from the ordeal of spaceflight was suspected to have been a contributing factor. That is hardly reassuring for would-be Martian mommas.
It remains to be seen whether human pregnancy and childbirth would be affected by the conditions on Mars, where gravity is about one-third that of Earth’s. But even if we can have kids there, would a child born on Mars be able to visit Earth? There are several reasons to think they may not.
First, a child born on Mars would grow up in that one-third gravity. This could weaken their muscles and make their bones more brittle. The same thing happens to astronauts in space, except that every astronaut so far has been an adult with a fully-formed skeleton. We don’t know for sure how a child’s body would develop in lower gravity, but there is a good chance it wouldn’t be able to handle a stroll on Earth, where they would feel three times heavier than on their native planet.
Sex keeps species together; a lack of sex is a well-known recipe for how to make a new species.
Second, Martian children would grow up without exposure to the microorganisms we constantly encounter on Earth. These microorganisms help to train our immune system, and while we will bring some microbes with us to Mars — some intentionally, others as microscopic stowaways — the vast majority won’t make the journey. There is a good chance that a Martian child would not be able to handle even the ordinary microbes we breathe in on a regular basis. Earth would make Martians sick.
So what does all this mean for romance on the Red Planet? Relationships among Martian settlers should be fine. However, even if we can figure out how to make and raise babies into healthy adults that live their lives on Mars, the future generations may gradually drift apart, adapting to the conditions of their distinct environments in much the same way that species of Galapagos finches evolved on different islands.
But the real trouble will come from interplanetary relationships. Put another way: Could you have a fling with a Martian?
Aside from the obvious problems of getting together for the holidays — given the six-month commute — even communicating would be tough. Earth and Mars are far enough apart that it takes at least three minutes to send a signal between the two planets when they are at their closest. Because Mars is farther from the Sun, its orbit takes longer than ours, so most of the time the two planets are even farther apart. The communication delay can be up to 22 minutes. If you’re patient, sexting would still be an option, but good luck having a video chat with your boo.
If you do manage to get together for a cosmic rendezvous, you risk sharing more than just a fun evening out. In addition to Martians having underdeveloped immune systems, the microorganisms that reach Mars will adapt and evolve, just as every other living thing does. Earthlings won’t have been exposed to these unique Martian microbes, making interplanetary interactions dangerous in both directions.
What happens if romantic relationships that span the Solar System aren’t just incredibly inconvenient, but so risky that they rarely happen or are verboten? Biologists know what happens when animals on different islands don’t get together to mate. Without a regular exchange of genes, they evolve in different directions and become increasingly divergent with each generation. Sex keeps species together; a lack of sex is a well-known recipe for how to make a new species.
So no pressure, but if you someday decide to move to Mars and your partner stays here, the very future of our species may be riding on how well you manage the ultimate long-distance relationship.