A terrifying thing happens to astronauts' fingernails on a spacewalk

Going on a spacewalk might sound like a lot of fun – but in reality it’s no walk in the park.

From their muscles getting less dense all the way to erectile dysfunction, astronauts have to put up with all sorts of things going wrong with their body.

And none more gross than what happens to their fingernails. Turns out they just fall right off.

The technical term for this is onycholysis, and it has to do with how much – or how little – atmospheric pressure there is in space.

Because there is so little ambient pressure in space, astronaut’s space suits need to be pressurised to keep the human body intact. But that’s not good for the hands, it turns out.

“Injuries to the hands are common among astronauts who train for extravehicular activity (EVA),” says a 2015 conference paper by space specialists Wyle Laboratories.

“When the gloves are pressurized, they restrict movement and create pressure points during tasks, sometimes resulting in pain, muscle fatigue, abrasions, and occasionally more severe injuries such as onycholysis.

“Glove injuries, both anecdotal and recorded, have been reported during EVA training and flight persistently through NASA's history regardless of mission or glove model."

A 2010 study looked at 232 hand injuries sustained by astronauts, and found that the wider your knuckle joints, the more likely you are to suffer in a space suit.

The study suggested that because space suit gloves limit the mobility of these knuckles, the fingers then get put under more pressure. This, in turn, means less blood gets to the fingers, and risks onycholysis. Ouch.

Work has been done to try to improve the design of space suit gloves, of course. One team found that the more tailored they were to each astronaut’s finger length the less likely they were to lose their fingernails.

That’s no mean feat, however. These gloves are made of at least four layers: one which touches the skin, one which helps create the pressurised environment, another one which makes the pressure layer less stiff, and an outer layer which protects the astronaut from everything on the outside.

Mercifully for NASA astronauts at least, they usually have their gloves fitted to each wearer, and with new space suit design moving forward each day, the number of injuries is decreasing.

Nonetheless, it sounds like a trip to space is no time for a manicure.

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