UCSB Science Line (2024)

There are different kinds of decomposition. The most rapid one is biological: bacteria and thebody's own enzymes both begin to break downtissues within a few hours of death. These arethe processes that we generally call rotting, andthey produce the bad odors that we smell. Nextare scavengers such as insects and other animals,but these probably won't be present in space,unless they hitched a ride in the spacecraft. Slower still would be heat degradation, whereproteins break down. Chemical exposure willdegrade what's left; bones will eventually decayin weathering, and oxygen will react with proteinsand many other things. This won't happen in spaceeither. Finally, very slow processes such asradiation would eventually break down moleculesover millions of years. The levels of radiationin space are higher than on Earth but not so highthat tissues would degrade very quickly.

Ithink there are three possibilities fordecomposition:
1. Unless there's a source ofheat nearby, the body will be quickly frozen, anddecomposition will take thousands or even millionsof years.
2. If there's heat, but no spacesuitor spacecraft, the body will very quickly dry out,because water evaporates extremely quickly in thevacuum of space. This will almost completely stopbiological processes, and the lack of air willprevent weathering and chemical degradation.
3.If the astronaut died while wearing theirspacesuit and the body stays warm, thendecomposing of tissue will be almost as fast as onearth. But bones will last almost indefinitely.Of course, if the body happens to fall in to aplanet, it will be destroyed by the extreme heatof re-entry into the atmosphere, like a meteorite.

I really don't know what effects radiation mayhave on a body decaying through bacteria but myguess is it wouldn't make much difference at thebeginning but stop the decomposition processsomewhere along the way. The astronaut's bodywould decompose from bacteria already insidehis/her body (just like anyone else). On the otherhand, the astronaut's suit and spacecraft shouldshield him/her from radiation. I hope this helps.

If he dies in his space suit, then yes, hewould decompose, because he still has bacteria andsuch within his body that would decompose him. Itwould use up all of the oxygen, however, so thedecomposition would become anaerobic very quickly,going from respiration to fermentation.

Radiation would not significantly affect thedecomposition process. It would break up chemicalbonds and such, but our deceased astronaut is morelikely to collide with an object of some kind likea meteor before that would really break himup.

If our astronaut is not in his suit,then the vacuum would kill the bacteriadecomposing him in fairly short order.