What happens if humans bone in space?

Don’t lie, the question has crossed your mind before. Now, NASA scientists are getting one step closer to answering it. Specifically: they want to understand the behavior of sperm in space.

Last week, alongside 5,800 pounds of supplies and experiments, NASA sent a couple of sperm samples to the ISS aboard a Falcon 9 rocket.

It might seem a silly use of resources, but NASA is trying to answer a question that has been plaguing us ever since we realized that humans would be eventually living in space (or at least going on extended space vacations): Can we reproduce in microgravity? As luxury space hotels and long-term Mars missions become a reality, so too will people who make babies (or at least try to) in space. So it’s good to start looking into how that might work out before it happens.

Sperm being prepared for launch. Image Credit: NASA

In Mission Micro-11, as it’s been called, astronauts on board the ISS will test if samples of human and bull semen (acting as quality control) can move freely enough and fast enough to potentially fertilize an egg, though, importantly, no egg is involved in the process. The researchers will then re-freeze the sperm and send it back to Earth, where another team of scientists will use technology similar to in-vitro fertilization to test if it’s capable of reproduction.

(Yes, there are six full-grown men on board the ISS right now, but NASA didn’t ask them to contribute in another way, “it’s understandable why the space agency didn’t go that route, if for no other reason than the limits of what can be reasonably demanded in even an outer space workplace,” as Live Science notes.)

The experiments are important because there’s evidence from earlier experiments that the lack of gravity might throw off how sperm function here on Earth. While sperm themselves might be able to move more freely in microgravity, the bigger challenge might be getting the sperm to fuse with the egg. “Delays or problems at this stage could prevent fertilization from happening in space,” according to NASA’s web site.

It’s not the first time we’ve studied sperm in space. In 2017, NASA found that frozen mouse sperm survived a 9 month trip to the ISS, and was able to produce healthy mice back on Earth. Scientists also showed that aquatic invertebrates were able to successfully reproduce in space back in 1998: snails and water fleas were able to continue life-cycles within a water-filled tank during a four-month trip aboard the Mir Space Station.

Even once we understand how sperm operate in space, there will still be questions. What about the intricacies of having sex in space? Can humans survive giving birth in microgravity? How will we overcome the massive amount of radiation levels? Will the lack of gravity affect children’s early development?

Science has laid the foundation, and NASA is finally going to find out if we will stand a chance as long-term travelers in outer space. But let’s take it slow.

Editor’s note (Tuesday 4/10/18, 5:15 PM ET): An earlier version of this piece misrepresented the nature of the experiments on the sperm. They are to determine how the sperm can fuse, but no egg is involved. The piece has been updated with the correct information, and we regret the error.