What would happen to a dead astronaut in space?

[Yora]

I've frequently seen pretty cool looking images of skeletons in space suits, but would that even be possible? Decay requires oxygen and there's isn't terribly much of it in a space suit. Also all kinds of microbes that might not be present in space ship and suit air either.

What would a dead astronaut in space look like after a century or so? The biggest factor would probably be solar radiation, so I'd take answers for both orbiting the sun at 1 AU and for drifting in interstellar space.

Any clues what degree of decomposition we could expect?

(Could we suggest such an experiment to NASA? Take a dead pig to space and tie it to the outside of the ISS for some months?)

[HandofShadows]

You need to take freezing into account and in deep space you would get a corpsical. In system you would get (uneven) heating from the sun which might be able to help with decay. But sooner or later everything in the suit including bacteria would die. If the suit was breached you would get a corpsical fairly quickly with little tissue decay. (But some tissue damage from the uneven presures.)

[factotum]

Yeah, it kind of depends where in space you are. Near a sun the astronaut probably wouldn't freeze, and the residual oxygen in their suit (assuming they didn't die from a suit puncture or something) might well be enough to begin the decay process, but I doubt it would be sufficient to keep things going long enough for all the flesh to decay--also, where would said decayed flesh end up going? It would be trapped inside the suit as some sort of horrible soup! Away from direct solar radiation the astronaut would eventually freeze and that would stop any residual decay dead in its tracks. So, overall, finding a suit with a clean skeleton and nothing else inside sounds cool, but would never actually happen that I can see.

[Storm_Of_Snow]

There are anaerobic bacteria which also cause decay (and could cause oxygen to be released to help feed the aerobic ones), which probably means you would get a soup, at least until stomach acids leaked out and mixed in to the soup which, combined with bacteria also working on any organics in the suit, corrode enough of the suit to breach it and what's left would be mummified as the liquids evaporated away. The suit may provide enough insulation to keep the bacteria at a working temperature (remember, it's not heating that's the problem in space, it's cooling).

[factotum]

The suit may provide enough insulation to keep the bacteria at a working temperature (remember, it's not heating that's the problem in space, it's cooling).

While true, there still needs to be a source of heat in there somewhere if your astronaut isn't in direct sunlight. The decay itself will provide *some* heat, but would it be enough to compensate for radiative losses through the suit?

[Trekkin]

A familiar decomposition process might begin, but it would not long continue before the air exhausted.

In order to maximize our air time, let's assume the occupant dies arbitrarily soon after donning a fresh EMU with a full PLSS. That gives us 1.76 kg of oxygen between the primary and backup tanks, feeding into a suit pressurized to 29.6 kPA and leaking at 100 SCCM. Assuming the temperature doesn't drop below the 285 K operating temp of the PLSS sublimator, the oxygen bottles should empty in 24 hours. (Of course this assumes the battery bricks can keep the sublimator running that long, which is probably going to depend on the thermal load of an LCVG with a corpse inside and which iteration of batteries our suit is actually using. The demand valves shouldn't care, though.) Do bear in mind that this assumes we aren't losing any volume to the sorbent canister.

Once the tanks are at ambient pressure, we have only the ~56 L of oxygen in the (occupied) EMU itself. Making the ludicrously pessimal assumption that the standard leak rate continues ad infinitum, in nine hours that suit is at near-vacuum. The actual suit pressure will of course undergo exponential rather than linear decay, but for our purposes the difference is likely to be academic within a day.

Given this timeline, I might expect a corpse in a spacesuit to be freeze-dried in the middle of the bloating stage, but before the emission of purge fluid. Green yes, purple no.

[Dodom]

There are anaerobic bacteria which also cause decay (and could cause oxygen to be released to help feed the aerobic ones), which probably means you would get a soup, at least until stomach acids leaked out and mixed in to the soup which, combined with bacteria also working on any organics in the suit, corrode enough of the suit to breach it and what's left would be mummified as the liquids evaporated away. The suit may provide enough insulation to keep the bacteria at a working temperature (remember, it's not heating that's the problem in space, it's cooling).

While I think the body is likely to freeze before its fluids can significantly corrode the suit, I want to underline your post as the only one who didn't assume that decay required oxygen. ^_^

[Trekkin]

While I think the body is likely to freeze before its fluids can significantly corrode the suit, I want to underline your post as the only one who didn't assume that decay required oxygen. ^_^

It does generally require air, though, and the two are synonymous in an EMU; they run at low pressure with pure oxygen so as to minimize the pressure differential.

If we were discussing, say, a disabled space station running an 80/20 oxygen/nitrogen air mix, then the distinction between CO2 removal, oxygen replenishment, and air pressure would be of paramount importance; one could imagine any number of failures in the life support system that would allow the air to become lethally toxic but remain at normal pressures, at which point anaerobic decay becomes likely.

A space suit, though, is a leaky human-shaped bag kept pressurized by an apparatus operationally similar to a demand valve on an oxygen tank; indeed, it is intended to lose pressure as CO2 is absorbed out of the suit atmosphere. When the suit runs out of oxygen, what remains is vacuum.

EDIT: regarding actually testing this, as Yora asked, the most feasible way I can think of would be to prepare a CubeSat containing biological samples and a sensor suite. Three pounds and a four-inch cube isn't much, but you could theoretically fit a mouse cadaver inside.

[snowblizz]

EDIT: regarding actually testing this, as Yora asked, the most feasible way I can think of would be to prepare a CubeSat containing biological samples and a sensor suite. Three pounds and a four-inch cube isn't much, but you could theoretically fit a mouse cadaver inside.

I still want to see the tape from the congressiona hearing about the dead pig that was sent to Spaaaace! :smallbiggrin: