I like knowledge! a.k.a. "Stiffs in Space!"

Q: And I also like the last question, from the comments section on the previous post: What happens to a body exposed to outer space? Would it bloat and freeze? Or would solar radiation burn it to a crisp? Should we eventually consider jettisoning our dead to save room on Earth for the living?

For completeness, here's that great question from Courtney that you mention:

Q: If we ejected dead bodies into space, would they decompose? All I know about space is there's no oxygen and it's cold. Would the body just freeze? And when reentering the atmosphere, would it become hot enough to totally cremate the bones, or just the rest of the body?

A: As you might guess, this has been a question that rocket scientists (and nervous astronauts) have been interested in for decades. Exposure to vacuum in space is not only a possibility for people traveling in spacecraft, it has unfortunately happened in at least one case. No bodies have ever been released into space, however, so the real-world effects of exposure of a corpse to hard vacuum are speculation so far. We do know some things, though, so I'll break down a few of the factors.

Vacuum and you

NASA, in preparation for launching men into orbit, ran a series of tests in "altitude chambers" where subjects were exposed to varying levels of air pressure, temperature, and radiation. Several things occur, in an increasingly dangerous and alarming sequence as air pressure drops around a living body. First, there is an explosive release of gases from the lungs and digestive tract. The effect, if the person tried to hold it in, would be something like the scene in Jaws when the rifle bullet ruptures a scuba tank in the shark's belly. Messy. Well, maybe not that dramatic, but you get the idea. Second, without air pressure to keep it liquid, water would boil away from the eyes and mouth, eventually boiling in the blood and heart. An immediate effect would be the bloating and bruising of soft tissues as they are inflated by the water vapor. Third, nitrogen in the victim's blood stream would start to fizz out and cause "the bends", a painful and disorienting state that divers often experience when surfacing too quickly from great depths. The final effect, (and the one that will actually kill you) is "hypoxia", lack of air to the brain that will starve it. Before that happens (around the first 10 seconds) the victim will have his or her wits about them before succumbing to disorientation and unconsciousness. After a minute or so of unconsciousness, they can still be revived with minor injuries. Shortly after, the brain dies.

One effect of a vacuum, however, may sound counter-intuitive. Because heat is usually most notably gained or lost through contact with air or water, a vacuum actually preserves body temperature for a long time. After a brief period of cooling down from evaporation, the body will stay relatively warm, compared to the extremely low temperatures of space itself. That means that the body will primarily dry out rather than freezing, so someone exposed to the vacuum will be in more danger of suffocation than dying of the cold. If left alone, the body would mummify, just like the pharaohs.

Radiation: sunny or toasty?

Sources seem to disagree on how much heat would be generated within the body tissues when unprotected in space. I've seen everything from "fried crispy" to "bad sunburn", but we are talking about a dead body in this case, so the difference is relatively minimal. There does seem to be agreement that solar radiation would not be strong enough to burn the body away. Well,... at least, not at first. The reality is that unprotected exposure to radiation in space would eventually break down the body at a cellular and molecular level. The body would become brittle and eventually disintegrate, bit by bit, over time.

(If you're interested in more detail, this article on Damn Interesting seems to have the best info gathered in one place. It's a great site to thumb through, in any case!)

Going home

I actually have very little data on what would happen to a body falling into atmosphere, but we can certainly guess. Objects from space are free-falling Earthward all the time. If you look at the sky in any place far from city lights, you can see them. Pfft! Gone. Most are tiny - from the size of a grain of sand to the size of a baseball. They create a light show as they generate friction with the air particles in the atmosphere, and burn up in the process. But here's the kicker - whether they reach the ground or not depends on the speed they were traveling when they got here. Small meteorites can reach the ground more or less intact if they were moving slowly, and a big meteor can break up into tiny pieces under enough atmospheric stress. So when you ask "would a body from space burn up entirely on reentry", the answer depends on the corpse's velocity when it hit the atmosphere. It seems that a body, being mostly carbon, would turn into charcoal pretty easily. In any case, I doubt you would find anything recognizable as a people part at the point of impact.

Space cremation for dollar$?

While the idea of saving lawn space for development by chunking our dead into space has some appeal, I doubt the economics work out. However, I'll just betcha you could make a pile of money charging people to have their ashes scattered in space. Oh, wait - someone's already done that.