The Science Behind Gecko Sex: How Will Humans Reproduce in Space?

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Why did Russian scientists put those ill-fated geckos inside a satellite? The point wasn't to make kinky gecko-sex videos in zero-G, but to learn more about the challenges that humans might face as they travel to destinations beyond Earth — and start raising the first truly space-born generation.

"Reproduction in space is a long-term goal that people would want to meet," Ruth Globus, rodent research project scientist at NASA's Ames Research Center, told NBC News. "Even if people were to say, 'We don't care about the long term, we only care about now,' it's important to understand what's happening to the ovaries and the testes [in the space environment], and the subsequent changes that may occur."

Russia's Foton-M4 experiment was aimed at furthering that basic understanding: The five geckos in the satellite (one male and four females) were just one part of the package. The mission sent other organisms, including mushrooms and fruit flies, into orbit for a month and a half to study how they propagated in the absence of gravity.

Despite what Internet wags may say, the sex wasn't what killed the geckos: Russian sources suggested that something went wrong with thermal control system inside the Foton-M4 satellite, causing the lizards to freeze to death. In contrast, the flies survived and successfully bred, according to Russia's space agency.

Fallen space animals

The geckos aren't the first animals to give their lives for space science: The list of fallen space animals stretches from Laika, who became the first dog to live (and die) in space in 1957, to the gerbils and mice who died last year in an earlier Russian orbital experiment. (The geckos on that mission survived.)

Animals are typically the trailblazers for the life sciences in space, Globus explained.

"We use animals because we can understand processes and adaptations to the space environment that we can't really study in humans," she said. "Whether it's a rodent, a gecko or other organism, the aim is to understand how those organisms respond to the space environment."

Globus' project is due to mark a milestone as early as this month, when the first Rodent Research Facility makes its way to the International Space Station aboard a SpaceX Dragon cargo capsule. Up to 10 mice will spend a month in the cage system, which builds on shorter-term experiments conducted during space shuttle missions.

The initial experiment serves primarily to validate the system, with a side study focusing on muscle-wasting in zero-G. At the end of their service, the mice will be euthanized, and tissue samples will be returned to Earth for study, Globus said. Eventually, researchers will be studying the effects of zero-G on the reproductive systems of female rodents.

'Disappointing' results

James Logan, a physician who spent 22 years working for NASA, says researchers need to focus much more attention on how the space environment affects reproduction and development.

"To my knowledge, they have never taken what I would call a fairly advanced mammal and gone from the first generation all the way through fertilization, gestation, birth, maturation and the reproductive cycle to the next generation," he told NBC News.

Some studies have been done with less complex forms of life such as frog eggs, or in earthly settings that simulate zero-G. "The outcomes turn out to be fairly disappointing, almost depressing," Logan said.

'We are no closer today to a real gravity 'prescription' than we were in 1961. In my opinion, that's a real indictment of the life science program at NASA.'

Logan's not surprised that reproduction doesn't work that well in weightlessness. "When you think about it, life on Earth evolved in a constant broth of gravity," he said. "Everything else changed — the ocean, the atmosphere, the continents, the climate — the one thing that never, ever changed since the origin of life was gravity."

Logan is surprised, however, that relatively little research has been done on creating artificial gravity in outer space, and seeing just how much gravity would be required for mammalian life to carry on from one generation to the next.

"Here's the problem: This is Year 54 of human spaceflight, and we are no closer today to a real gravity 'prescription' than we were in 1961," he said. "In my opinion, that's a real indictment of the life science program at NASA. If you want to look at gravity as a medication, so to speak, we don't know the dose, we don't know the frequency, we don't know the side effects."

Long-term view

Maybe we don't need to know, as long as space travel is limited to sending crews into low Earth orbit for six months or even a year at a time. But if we're talking about settling on Mars, where the force of gravity is only 38 percent of Earth's, it's important to know if a low-gravity environment would result in sterility or worse.

"If 0.38 G does not work, then you've got a problem," Logan said.

Ironically, one of the first space projects to catch the eye of Elon Musk, SpaceX's billionaire founder, was a satellite mission aimed at seeing whether mice could reproduce in Mars-type gravity. More than a decade later, that kind of experiment still has not been done — neither with mice nor with geckos.

"It's not an easy thing to do," Logan acknowledged, "and to do it right would probably take on the order of 15 to 20 years. ... But if we're not willing to do that, it's safe to say we're not going anywhere in interplanetary space anytime soon."