As far as we can tell, no human has ever had sex outside of the confines of Earth's gravity (unless some freaky stuff has been going on aboard the ISS). As a result, a lot of questions remain unanswered: what would sex look like in sterile, zero gravity conditions? Or on Mars? How about childbirth, or natal development?
"Not only how our reproductive systems adapt to the space environment, but if we actually want to go places, and we want to stay there – if we're talking about colonization, there's a key component to colonization that makes it possible, and that is having babies," said Kris Lenhardt, assistant professor in the department of emergency medicine at The George Washington University School of Medicine and Health Sciences, during a May panel.
"This is something that we, frankly, have never studied dramatically, because it's not been relevant to date. But if we want to become a spacefaring species and we want to live in space permanently, this is a crucial issue that we have to address that just has not been fully studied yet."
Bit by bit, researchers are coming around to what Gene Roddenberry realized half a century ago: space sex is super important, which is why all the ladies on the Starship Enterprise wore go-go boots and miniskirts. A group of Japanese scientists freeze-dried mouse sperm and stored it on the ISS for nine months, and then unfroze it to see if they could use it to artificially inseminate female mice.
The experiment was a success, showing that high levels of space radiation aren't necessarily a barrier to reproduction. But that was only sperm, and from an exceptionally fecund animal at that. It isn't clear how a human embryo, created in space or on a distant world, would fare because nobody has ever tried it before.
"We have no idea how they're going to develop," said Lenhardt. "Will they develop bones the way that we do? Will they ever be capable of coming to Earth and actually standing up?"
Even after a successful birth, there's also the concern of what a child reared in micro or lessened gravity will look like. Low gravity and space radiation already pose major threats to adult spacefarers, let alone tender youths.
"So we're basically, at that point, talking about people who are going to be – if they exist in the future – are going to be vastly different from what we are. And that may be kind of a turning point in human history," Lenhardt said.
That doesn't even touch on the physical challenges of sex in space. You may take it for granted, but almost everything fun you can do with another person also involves your good friend gravity.
"The first challenge is simply the result of moving about in near-zero gravity: every push or thrust will propel the astronaut in the opposite direction," John Millis, chair of the department of physical sciences and engineering at Anderson University, told Gizmodo earlier in June. "Imagine a pair of ice skaters standing on fresh ice: if they were to push their hands against one another, they would each shoot backwards away from each other.
Microgravity interfering with blood flow and pooling might also make it more difficult for male astronauts to induce an erection (as if they needed another excuse, am I right ladies?) Females might have difficulties as well for similar reasons.
"Because of the micro-gravity environment, sweat and tears don't run down the astronaut's bodies like it does here on Earth, instead it pools like small ponds of fluid near where it was secreted," Millis said, disgustingly. "If the motion is vigorous enough it could be ejected from the surface of the body. This means that liquid would both be pooling on the body, especially where there is contact with the other person. Also, the more they moved, pools of liquid would be flying off around the couple."
Neither Lenhardt nor Miller touched on the ever-popular notion of sex with aliens, which is obviously what everyone cares about. Until we can conduct sexual anthropology on wookies or turians, however, that subject will remain one of popular and not academic interest.
