QotW: Would a body in space decay?

The body of a floating astronaut would have to decompose eventually, wouldn't it?
12 October 2021


Floating astronaut



Listner Daniel wrote in to ask, "If a crew on a mission to mars had a death on board and the body was released into space, would that body ever decay?"



Harry Lewis floated this one to Matthew Bothwell, public astronomer at Cambridge University. Fortnautely for us, Matt wasn't deterred by the sinister concept... 

Daniel - If a crew on a mission to Mars had a death on board and the body was released into space, would that body ever decay?

Harry - Cue public astronomer, and close friend of The Naked Scientists, Matthew Bothwell from the University of Cambridge...

Matthew - What a cosmically creepy question! The answer is that no, a body exposed to the vacuum of space wouldn't decay in the way that bodies decay on Earth. In fact, in outer space, you'd ended up being preserved quite nicely. One important factor is that a body in space would dry out really quickly. The boiling temperature of liquids depends on the pressure, so lower pressure means a lower boiling point. In space where there's no pressure liquids just instantly boil, which means turn into gas. So a body ejected into vacuum would lose all its liquid quite quickly and become sort of mummified.

Harry - Similarly, if you were ejected into space without a spacesuit, after 14 seconds you'd experience the evaporation of water in your mouth. It would feel like an odd tingling sensation on the tongue.

Matthew - Another factor is that the lack of atmosphere makes space a hostile environment for bacteria. So a body in space wouldn't be broken down by bacteria in the same way that a body on earth would be. A lot of what we think of as a body decaying is the action of bacteria and that wouldn't be happening. One misconception about bodies in space is that people often think they would instantly freeze. This isn't true. You feel cold on earth when the atmosphere around you is at a low temperature. That is, the molecules in the gas around you have less energy than the molecules that make up your body, and so when the air hits your body it steals a bit of your energy and you cool down. But in space there's no atmosphere, and so you don't lose heat very effectively

Harry - Vacuums are really good at maintaining temperatures - just think about your thermos vacuum flask, capable of maintaining a constant temperature and allowing you to enjoy your coffee or soup hot later on in the day

Matthew - A body in space would freeze eventually, but it would have to freeze by losing heat radiation, which would take a lot longer than you might expect. So overall between the dehydration, the lack of bacteria, and the eventual freezing, a body in space would end up being very well preserved

Harry - Thanks for that Matt. You're drudging up memories of Battlestar Galactica there for me! Next week will be a tad closer to home whilst we endeavor to find out more for science teacher Ellie and one of her pupils...

Ellie - One of my students asked me a question that I couldn't answer..

Student - Hi Dr. Chris. I'm a Year 9 student from Manchester and I've got one blue eye and one brown eye. When I have kids, are they going to have a blue eye and a brown eye like me?


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