The Artemis programme is the opening chapter of NASA’s long-term goal to establish bases on both the Moon and Mars.
Having a long-term presence in space is the first step toward space settlement – having people truly living in space. NASA is not alone in this ambition.
Becoming a multi-planetary species is the stated goal of SpaceX and other spacefaring nations like China are developing similar plans.
But to truly live in space involves one biological necessity that cannot be overlooked: reproduction.
Yet significant gaps exist in our understanding of how human reproduction might be affected by the conditions in space.
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Has anyone ever had sex in space?
As far as we know, no one has yet had sex in space.
There was speculation in 1992 when NASA sent two newlyweds, astronauts Mark Lee and Jan Davis, into space for eight days aboard the Space Shuttle Endeavour.
However, there was very little privacy aboard the Space Shuttle, so an orbital rendezvous would have been difficult to conduct discreetly.
The International Space Station, which has been continuously occupied since 2000 and often features mixed-sex crews, likewise lacks much in the way of private spaces for intimate moments.
How to get intimate in zero gravity
But privacy is not the only challenge for anyone hoping to join the 250-Mile High Club. In microgravity, any objects that collide repel one another.
Creative solutions to solve this problem have been proposed, including a device called the Snuggle Tunnel invented by Sam Coniglio, author of the book Creature Comforts in Space.
Another is the 2suit, invented by Vanna Bonta in 2006, which is a flight suit with a large front flap that can be opened and attached to another 2suit via Velcro strips.
Assuming that this step is achievable one way or another, the next issue is fertilisation.
Can fertilisation really occur in microgravity?
A study published in March in the journal Communications Biology found that human sperm become disoriented in conditions that simulate microgravity.
The result was a 30% decline in the number of fertilised eggs. Other studies using human and animal sperm have found mixed results, leading to some uncertainty as to whether or not fertility rates are likely to be affected by lower gravity conditions.
Embryo and foetal development is another unknown. Some fish embryos have developed successfully in space, but little work on this critical stage in reproduction has been done using animals more biologically similar to humans, such as rodents.
One 1983 study sent 10 pregnant rats into space on a Soviet satellite.
They were at a stage in their pregnancy that corresponds to the beginning of the third trimester in humans, when the foetus is developing its bones, muscles and organs.
The rats gained less weight than rats at the same stage of pregnancy on Earth, suggesting that conditions in space may have had a negative impact on either the pregnant female rat or its developing pups.
The satellite returned to Earth before the rats could give birth. Five of the 10 were sacrificed and dissected, revealing that the foetuses had survived.
Some of the placentas, however, had haemorrhaged. The other five rats completed their pregnancies, with four of them giving birth to healthy pups.
The fifth lost her entire litter when the first pup got stuck in the birth canal.
The problem with pregnancy
Pregnancy and childbirth could be especially hazardous for women whose muscles and bones have been weakened by prolonged exposure to lower gravity.
Astronauts in a weightless environment lose bone density at an average rate of 1.5 to 2% per month.
We don’t know for sure how partial gravity, such as the 0.166 g of the Moon or the approximately 0.379 g of Mars, would affect bone density, but a woman who has spent her entire life in partial gravity is likely to have at least somewhat compromised bone strength by the time she reaches adulthood.
The extra strain of pregnancy and childbirth could make both more dangerous than they already are.
Any child that is born on another planet could develop weaker bones and muscles, which would make it difficult to travel to Earth.
A person born on Mars would weigh three times as much on Earth. Tolerating that with a weakened skeleton might be impossible.
Getting sick in space
Yet another complication is exposure to microorganisms that are common on Earth but absent from a space settlement.
Studies of astronauts’ microbiomes and of the ISS show that microbes travel with us to space, but those that come along for the ride will be a tiny subset of all the microbial diversity on Earth.
A person whose immune system has never encountered a bacterium or virus can be more susceptible to dangerous infections.
As such, microbial life may become the greatest factor limiting interplanetary travel for future space settlers
Likewise, travellers from Earth will likely be exposed to novel strains of bacteria and viruses that mutate and evolve after arriving in a space settlement, making them equally dangerous for newcomers.
A new stage in human evolution?
If it does indeed become difficult for people born on different worlds to get together, the populations of each planet will begin to diverge.
Much like plants and animals isolated on different islands, prolonged separation leads to evolutionary changes that eventually give rise to new species. In other words, the inhabitants of Mars may eventually become a different kind of human – they would become Martian.
Whether this is a future we see as desirable is a matter of opinion. It is possible to draw a straight line from creating human settlements on other worlds to the origin of new human species, but we are not there yet.
No human has yet set foot on Mars, and there are many questions for which we do not yet have answers.
Can we have sex in space? Would a child conceived and born on another planet grow into a healthy adult? Is interplanetary travel possible for natives of those worlds?
While we aren’t yet sure about the answers to many of these questions, opportunities to answer them seem to be around the corner. They begin, like all great adventures, with one small step.
You might even call it a baby step.
