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Soyuz MS-22 -

Fear became reality for cosmonauts Sergey Prokopyev, Dmitri Petelin, and Frank Rubio, who were on a six-month space mission aboard the Soyuz MS-22 in 2022. They became stranded in orbit when the Soyuz MS-22 capsule was hit by a meteor and developed a leak.

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Soyuz MS-23 -

The trio returned to Earth safely via the Soyuz MS-23 spacecraft after a prolonged stay of approximately 371 days. These astronauts were safe inside their pressurized spacecraft, but what would happen if they were stranded without a ship?

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Has anyone ever gotten lost in space? -

Thankfully, there has never been an astronaut irretrievably stranded in space before. Bruce McCandless was the first astronaut to make an untethered spacewalk on February 7, 1984.

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Bruce McCandless -

McCandless reached a distance of 320 feet (97 meters) from the Challenger space shuttle. He used nitrogen gas thrusters to propel himself from the shuttle, paused for a photo, and then returned to the safety of the spacecraft.

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Deaths above the Kármán line -

Most fatal accidents involving astronauts have occurred during launch, return to Earth, or other phases of space missions. There have only been three deaths that have happened in space above the Kármán line. 

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What is the Kármán line? -

The Kármán line is the boundary separating Earth's atmosphere and outer space. It is between 50 and 62 miles (80 and 100 kilometers) above mean sea level.

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Soyuz 11 -

 In 1971, Soviet cosmonauts Georgy Dobrovolsky, Viktor Patsayev, and Vladislav Volkov died when Soyuz 11 malfunctioned upon undocking from Salyut 1 while in space above the Kármán line. A valve opened, exposing them to space's vacuum and lack of oxygen. Their bodies were recovered from the spacecraft after landing.

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How would you die if you got lost in space? -

If someone were to become lost in space, the amount of time they had to survive would depend on whether they were wearing a spacesuit or not.

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Spacesuits -

Spacesuits provide the astronaut's body with proper pressure, oxygen, and warmth. The oxygen tanks allow for a maximum of between 6.5 and 8.5 hours before they need refilling. 

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Hypoxia -

If an astronaut was lost in space wearing their spacesuit and had run out of oxygen, they would eventually die of hypoxia, a condition in which the body is deprived of adequate oxygen supply at the tissue level.

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How would you die if you weren't wearing a suit? -

If an astronaut was lost in space with no way to return and wasn't wearing a spacesuit, death would occur within a minute, about 50 seconds after loss of consciousness.

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What would happen to the body? -

The body would be exposed to the vacuum of space, the absence of atmosphere, and the extreme temperatures of open space.

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The liquid in the body would boil -

At lower pressures, liquids boil at much lower temperatures than on Earth. Since 60% of the human body is made up of water, this would have dire consequences for an astronaut lost in space.

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Oxygen and the brain -

No atmospheric pressure means that the oxygen dissolved in the blood will begin to escape and will no longer be delivered to the brain. Loss of consciousness will happen after about 10 to 15 seconds.

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Air in the lungs -

All of the air would be sucked out of the lungs. While it might seem best to hold onto the remaining air as long as possible, it would quickly expand and cause the lungs to rupture.

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Extreme temperatures -

Temperatures in space are extreme—extremely cold in the shadow of objects and intensely hot in direct sunlight. On the Moon, temperatures can range from about 248°F (120°C) in sunlight to minus 248°F (minus 120°C) in shadow.

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How would your body decompose in space? -

On Earth, decomposition after death begins almost immediately. Blood pools due to gravity in a process called livor mortis, the muscles stiffen in a process known as rigor mortis, and bacteria and enzymes begin to digest the body's soft tissues.

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How would your body decompose in space? -

In space, the usual processes of decay cannot take place. Without gravity, blood does not pool, and the absence of oxygen significantly impedes bacterial activity. Depending on the temperature, the body may freeze solid or dry out to a jerky-like consistency.

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The body won't explode -

Space movies often depict a body exploding due to the lack of pressure in a vacuum, but in a series of experiments conducted by NASA in the 1960s with dogs, chimpanzees, and squirrels, none of them exploded.

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Radiation exposure -

A lost astronaut in space would be exposed to cosmic rays (radiation) and solar winds (charged particles emitted by the Sun). Without a spacesuit, this exposure would be fatal.

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Hit by micrometeoroids -

An astronaut lost in space could be struck by high-speed micrometeoroids—tiny particles of dust or rock—or by debris from satellites or spacecraft.

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Would the body eventually leave the solar system? -

If death occurred in Earth's orbit, the body would likely remain in orbit around Earth, just like any other object. If the astronaut were lost beyond Earth's orbit, their body could leave the solar system or become caught in the gravity of another planet.

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Would the body eventually leave the solar system? -

If the body was sealed in a space suit, decomposition would only last for as long as the oxygen lasted. Ultimately, the body could drift in the endless expanse of the universe for millions of years.

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Would the body eventually leave the solar system? -

Eventually, a body in space may fall back into the atmosphere, which would cause it to burn up due to the intense friction and heat generated during re-entry.

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What would happen if someone died on the International Space Station? -

While there's no official protocol to handle a sudden death on the ISS, keeping the body inside a spacesuit somewhere cool eliminates the risk of a biohazard.

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The Body Back -

In 2005, NASA commissioned a study into a design called the "Body Back" using a technique called promession, which essentially freeze-dries a body by exposing it to extremely low temperatures and then vibrating it into a powder, making it easier to store and transport remains in space.

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Jettison -

If freeze-dried cremation wasn't an option, space crews could jettison the body into the void. While the UN has rules about littering in space, this may not apply to human bodies.

Sources: (News Week) (Space) (Howstuffworks) (BBC) 

See also: A history of famous firsts in space

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