Being an astronaut is an awe-inspiring job, but there are plenty of risks that come with spacewalks - as demonstrated by one scary incident.
Italian astronaut Luca Parmitano was on a spacewalk outside the International Space Station in 2013 when he noticed a weird sensation - it felt as though his helmet was filling up with water.
A video from the incident shows that Parmitano acted quickly and immediately contacted mission control to note the odd feeling, and after they questioned him a little it became clear that something was definitely wrong.
Parmitano wasn't sweating anywhere near enough to account for the moisture he was describing, and it seemed to be growing in volume, with zero gravity making it hard to really tell exactly what was happening.
The seals in Parmitano's suit meant that this was a little bit like having his head stuck in a fishbowl with water trickling into it, as he'd later describe in a video for the European Space Agency (ESA).
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With water pooling in pockets around his helmet, getting nearer to his face, and with the risk of drowning very much a real one even though he was up in space, mission control quickly called Parmitano back into the space station.
Parmitano's crewmates were waiting for him and helped take his helmet off as quickly as possible, with towels on standby to absorb the water once it was open (since water moves in a way that is more challenging to clean up when you don't have any gravity).
If all of that sounds cool, calm and collected, Parmitano's own description of the ordeal makes it clear just how scary it really was.
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In the ESA video, he said: "The water kept trickling until it completely covered my eyes and my nose. It was really hard to see. I couldn't hear anything. It was really hard to communicate. I went back using just memory, basically going back to the airlock until I found it."
Being unable to see while on a spacewalk outside the International Space Station isn't something that most of us could ever imagine dealing with calmly, so it really underlines how much of being an astronaut comes down to staying rational under real pressure.
Still, Parmitano survived the situation and, while he acknowledges that it was scary, he doesn't seem to have any regrets about his profession, just perspective.
In a 2013 blog post, Parmitano wrote: "We are explorers, not colonizers. The skills of our engineers and the technology surrounding us make things appear simple when they are not, and perhaps we forget this sometimes. Better not to forget."