The first woman ever to fly in space was Russian cosmonaut Valentina Tereshkova, who launched into low-Earth orbit in 1963 aboard the Vostok-6 capsule. Tereshkova reconfirmed how awesomely tough she was five decades later, when—at that point a 76-year-old—she said that she'd drop everything to fly to Mars, and never come back.
"Most likely the first flight will be one way," Tereshkova said to journalists in Star City, Russia, where the cosmonauts train, on the fiftieth anniversary of her flight.
"But I am ready."
Many remarkable women have traveled into space: Sally Ride, who was the first female NASA astronaut, and physician Mae Jemison, the first black woman to leave Earth. Then there's the European Space Agency's Samantha Cristoforetti, who spent 200 consecutive days living in space, the longest stretch for any woman. Roberta Bondar, Chiaki Mukai, Anousheh Ansari—the list goes on.
But no woman has travelled beyond low Earth orbit: Of the 12 astronauts who've visited the Moon, all have been men. No woman has lived in space for an entire year, a milestone recently achieved by Scott Kelly, who became the first NASA astronaut to do it. Since Yuri Gagarin was shot into space, in 1961, a total of 543 humans have left Earth, according to a 2016 report from Gregor Reid and Camilla Urbaniak at Western University in London, Ontario.
Just 11 percent have been women.
There's an important consequence to this. Life in space is full of risks—astronauts have to deal with radiation, possible vision and bone loss, and a huge range of other challenges—and men and women are affected differently. Because we fly fewer women, scientists know less about how they respond to life in zero gravity.
"There have been very few female long-duration astronauts," said Cristoforetti, who spoke with Motherboard following the premiere of A Beautiful Planet, a new IMAX film showing Earth from space. "And so we haven't had any research, really, into the differences [between how men and women experience space travel]," she continued, "because the numbers are so small." Anything that has been observed could just be an individual variation, and not hold true across a larger group.
Based on what scientists have learned from studies on the ground, "it's reasonable to assume" that space travel could affect men and women differently, at least in some ways, she said. (This gender bias isn't just true of space studies, either. It's also been a longstanding problem with Earth-based research.)
For example, on Earth, women tend to develop cardiovascular disease seven to ten years later than men, thanks at least in part to the protective effects of estrogen. Radiation is a major concern in space, and female astronauts have a 20 percent higher risk of developing cancer (mostly because of ovarian and breast cancers), according to Reid and Urbaniak's study.
Beyond that, urinary tract infections—UTIs—are the bane of any woman's existence, but men don't suffer from them as often. UTIs are a big problem in space, where they seem to occur more frequently in women. And men are more likely to develop kidney stones, a major risk for astronauts: in zero gravity, bones shed calcium, which turns into kidney stones.
Before we fly a woman on a long-distance mission to Mars or an asteroid, it's critically important that we understand how they respond physically and mentally to life in space. Otherwise, a female astronaut might get halfway to Mars only to develop the world's worst UTI (or something even more awful), but be unable to turn the ship home.
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Gregor Reid, who is a professor of surgery, microbiology and immunology at Western, has spent the last three decades studying bacteria—"long before it became trendy," he told Motherboard. A main focus of his work is how probiotics benefit female health.
Recently, Reid became interested in female astronauts, a group he hadn't studied before. "A postdoc came over from Russia, who told me that Russian cosmonauts take probiotics," he recalled. "That gave me a starting point, although there was very little literature, certainly not in English." He decided to do a study of his own, with co-author Urbaniak.
In their paper, the two look at whether probiotics could help female astronauts prevent or treat some of these conditions.
"Men and women differ in many ways, which includes the risk of acquiring certain diseases," the paper says. Earlier studies have shown that the bacteria in astronauts' noses, mouths and guts is altered during spaceflight, although scientists don't really understand the cause of this yet, or the consequences.
One major limitation of these studies "is that they were conducted in male astronauts," the paper says, "with no data available on how space travel affects the microbiota in females."
Treating a UTI on Earth often means taking a course of antibiotics, but those drugs don't work so well in zero gravity (and bacteria can become more virulent, according to NASA). To get around this, Reid and Urbaniak propose that female astronauts could take probiotics as a preventative measure, which has been effective in studies of elderly women on Earth.
"The whole idea of going to Mars is to [create] another human existence, especially if Earth goes belly up. You're going to need to send women"
Cancer, too, is a major concern—one that puts women at higher risk when they head to space, say the researchers. While probiotics aren't a cure, they might have some preventative effect: studies in large populations have shown that women who drink fermented milk, like yogurt or kefir, have a lower incidence of breast cancer, according to the report. Women are also more likely to suffer from irritable bowel syndrome, and spaceflight seems to provoke diarrhea, maybe from stress, Reid said. Probiotics could help address that on a long mission, too.
As for how to carry probiotics into space, Reid proposes creating some kind of dehydrated, bacteria-laden sachet, which could ferment milk into a sort of space yogurt.
When asked whether the lack of research into female astronauts means that risk-averse space agencies would be less likely to fly a woman to Mars, at least the first time around, Reid said no. "The whole idea of going to Mars is to [create] another human existence, especially if Earth goes belly up," he said. "You're going to need to send women."
If they're gone for many years, "they might have a baby," he continued. "What are the implications? If they get breast cancer [in space], flying back to Earth won't be the solution."
It's true that we still know very little about sex and reproduction in zero gravity, although scientists are starting to study it. In Space Pup, as one NASA experiment is called, astronauts are keeping freeze-dried mouse sperm on the International Space Station for two years. Then, scientists will use it to try to impregnate mice on Earth, to see what happens.
Scott Smith, who heads the Nutritional Biochemistry Lab at NASA's Johnson Space Center (where the astronaut corps is based), has done plenty of studies on space travellers. One issue he's been looking into is why some astronauts suffer vision loss in space. That's considered one of the major risks of spaceflight, but we still don't know if female astronauts are susceptible to it. So far, all the astronauts who've reported this problem are men. Scientists can't say yet if that's because it doesn't affect women as much, or because we just haven't flown enough of them to space to see it in this group.
In a recent study, Smith found that genetic differences could make some astronauts more susceptible to vision loss. "Obviously we've flown fewer females than males," he told Motherboard. "But we study astronauts very intently with a series of experiments, usually as many as can be done on any mission, regardless of their sex."
Studying astronauts is challenging enough, Smith continued. There are so few people who've been into space that doing a big epidemiological study is impossible.
"If you go back 10 or 15 years, you were lucky if you published a study of six people, let alone men and women," he said. The Space Station, an Earth-orbiting lab, has changed that. "The station has given us a solid platform where we have lots of folks flying." The vision loss paper, he noted, had a sample size of 49 astronauts—a whopping number for this type of work.
Studying astronauts isn't just important for space travel. It can also tell a lot about people who'll never leave Earth: for example, studies of astronauts' vascular health and blood pressure have provided insights into what happens when we age. "It's an opportunity to understand how the human body works," Cristoforetti told Motherboard. And that applies to women as well as men.
Sending anyone on a long-distance mission, male or female, is a gamble. When it happens, space agencies will want to be absolutely sure they're prepared for every imaginable contingency. Until we know what the risks are, it seems unlikely we'll send a woman to Mars, an asteroid, or somewhere even more exotic—no matter how "ready" these female astronauts are, as Tereshkova clearly was.
"We need more studies," Reid said. "And we need more women in space."
Silicon Divide is a series about gender inequality in tech and science. Follow along here.