Yes, you can drown in space

As if the cold vacuum of space potentially robbing you of life-giving oxygen weren't scary enough, a routine spacewalk aboard the International Space Station was called off today when an astronaut's helmet filled up with water about an hour into a repair mission.

Liquid behaves differently in low- to zero-gravity, as astronaut Chris Hatfield demonstrated for us in this cool experiment; instead of flowing down it floats and clumps together. Italian astronaut Luca Parmitano got a good look at the phenomenon when his helmet began filling with what appeared to be a half-liter of liquid, drenching his eyes, nose, and mouth, and crippling his ability to hear or speak. Although NASA "seldom cuts a spacewalk short," reported Fox News, Tuesday's accident was the exception, since "Parmitano could have choked on the floating water droplets in his helmet."

In other words: Just imagine all the water floating before your eyes in a bowl just a little larger than your head.

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While the source of the fluid is unknown, the likely culprit is his in-suit drinking bag. The pouch is attached to the inside the suit's upper torso with velcro, and allows him to take sips during spacewalks, which can last up to 8 hours at a time. (Apparently, though, Parmitano said the liquid didn't taste like drinking water. Perhaps it mixed with his nervous sweat — and understandably so.)

In Parmitano's case, his crewmates were able to remove his helmet upon re-entering the ISS and towel him off. "He looks miserable. But OK," his spacewalk partner, astronaut Christopher Cassidy, told Mission Control down in Houston.

The mishap highlights just how hapless our fragile human body is when it's crammed into a clunky spacesuit, which is designed to protect us from space's brutal elements (like radiation). Combined with our body's natural impulses, the suit's restrictions can make us extremely uncomfortable: Just ask Alan Shepard, the first American who flew up to space in 1961, but not before soaking himself with urine after hours of delays.

But what happens if you aren't wearing a spacesuit on a spacewalk? According to NASA, "You do not explode and your blood does not boil," as is widely believed — you have the containing power of your skin and circulatory system to thank for that.

Still, the nightmare scenario painted by today's aborted mission showcases just how much can go wrong when you're 17,000 miles above the Earth.

Officially, only three humans have ever died in outer space: A trio of Russian cosmonauts who asphyxiated aboard 1971's Soyuz 11 spacecraft, when their capsule depressurized prematurely upon re-entry. In one of the more frightening moments in space exploration history, a rescue crew opened the hatch of their apparently undamaged craft, only to find the three cosmonauts still strapped into their seats, unresponsive and lifeless.