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Where Can You Take Off Your Space Helmet in the Solar System?

Nevermind NASA's explicit instructions to keep your helmet on.

When you go to space, NASA has very explicit instructions to keep your helmet on. But Fraser Cain, publisher of UniverseToday.com and co-host of AstronomyCast.com, wanted to know if there's anywhere in the solar system where you'd survive without a helmet. In this video, he explains where and why you need a helmet, and where you could theoretically take it off.

To begin with, astronauts wear helmets to protect themselves from the "hard vacuum space" in which all the air would rush out of their lungs and they'd be unconscious within 45 seconds. Starved of oxygen, they'd die shortly of suffocation.

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So the most obvious place in the solar system where you wouldn't die instantaneously without a helmet is Earth. This might sound tongue-in-cheek, but Cain uses it to explain the conditions humans require in order to survive, that is without a helmet.

The human body needs just the right amount of pressure to keep the lungs inflated: Not enough pressure, you'd suffocate, and too much pressure your lungs would crush and your heart would fail.

Humans need atmospheric pressure between .5 and five times the atmosphere of Earth. That pressure can be in the form of air, or otherwise water or gas. Humans also need to make sure the surrounding temperature is not too hot or cold for them to handle. Ideally, for humans to thrive, the air they breathe should have elements of both oxygen and nitrogen.

There are a few other places in the solar system where you can take off your helmet, albeit briefly, without dying instantaneously. The cloud coverage of the planet Venus is one of those places, where the air pressure is 65 percent that of Earth's and the temperature is around 37 degrees Celsius. The problem there, however, is that the region's sulfuric acid cloud layer is toxic to humans, while Venus' carbon dioxide atmosphere would have them asphyxiate. Hypothetically, with an air supply and and protective suit from the sulfuric acid, humans could survive without a helmet for a few minutes.

The surface of Titan also has a pressure of 1.4 times that of Earth, while the temperature is -179 degrees celsius. Again, hypothetically, you could take off your helmet for a moment before your face freezes.

There are also water reservoirs under many moons and objects in the atmosphere, as well as gaseous regions where you could temporarily take off your helmet. While none of this is recommended—or allowed under NASA's hardline safety rules—hypothetically it's possible to take off your helmet. The only question is, would you survive long enough to put it back on again?

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