MadSci Network: Astronomy
Query:

Re: Can a carbon-based lifeform survive in space without a suit?

Date: Tue Oct 17 10:36:07 2000
Posted By: Scott Kniffin, , Nuclear Engineer, Unisys Corporation
Area of science: Astronomy
ID: 970573034.As
Message:

Lynton,
I think I'll tackle this more as a philosophical question as opposed to a hard science question and answer. It deserves at least that much for something so speculative.

At this time, I wouldn't think that anything could. I say "at this time" because in so many cases, science fiction has a habit of becoming science fact; but that doesn't mean that there is any likelihood of it happening anytime soon though. You might have to wait until the time frame of, say, the "Tinman" episode of Star Trek: The Next Generation. Here are a few of the problems facing this concept:

Temperature

Interstellar space is cold. Really cold. Like 4 Kelvin cold. Not a particularly hospitable environment. Now if you happen to have full exposure to a nearby star, the opposite condition becomes a problem rather quickly as you don't have that convenient thing called an atmosphere to play filter-out-the-tough-stuff. It actually gets uncomfortably hot rather quickly. Space suits do not heat the astronaut; they contain a chiller to cool them off. (I'm always amazed by the number of people that don't know this.) The reason being, in a vacuum, conduction and convection no longer apply as a means of heat removal; that leaves radiation, which is the least efficient means of heat transfer. If Nature had a face I'd have to accuse her of having a mean sort of sense of humor as this sort of problem always seems to want to crop up, but then again, that's what makes my job fun and challenging.

Radiation

The space environment, particularly around stars is rather hostile in this respect and planets have a neat habit of collecting extra bits to make it worse. The Sun kicks off lots of protons, electrons, helium, and the occasional heavier ion in the course of the day. This makes up what we call solar wind. We say wind because it really does exert a pressure (albeit not much) and it is moving at a few million kilometers per hour. Nothing to sneeze at, but just not as strong as one in a localized sense. (Now across a few square kilometers...) The Earth's magnetic field also traps some radiation in the form of high-energy protons and electrons in regions known as the Van Allen belts. An interesting side effect to having a gigantic shield to defend us from the worst solar storms. These belts just play havoc with satellites. The last ingredient in our radiation soup is galactic cosmic rays. These are ions of virtually every element all the way through uranium that have been accelerated to truly unbelievable velocities, usually by a stellar explosion several billion years before. They tend to be quite nasty to satellites and are responsible for the sudden death of a few birds we've put up over the last few years.

Why does all this matter? Radiation effects on biological systems. Living things can only take so much damage before they can no longer function and radiation does a rather neat job of damaging things. (Nowhere near as bad as many people think, living things are rather radiation resistant.) It's just that space has no shielding.

Food

Planets and stars represent most of the matter, and it's a long way between rest areas with the fast food shop next to the gas station.

So if I were building a biological spacecraft, it would have some sort of thick shell that is capable of alternately radiating/reflecting or absorbing heat depending on the requirements of the moment. That thickness would also have to do a good job of shielding out the lower energy radiation. It would have to be huge so it didn't starve along the way to the next rest stop. Now if I could just figure out what it "eats" to get by. Perhaps it would have a biological fusion reactor? (Now we're really getting out there.) Oh, one other rather important thing, the water recycling system would really have to be nearly perfect. One thing I can say with reasonable certainty is that where there is water, there is life on the planet earth. No water, no life. So there you have it.

Now on to the silicon question. I will say the following and much could be debated, disagreed with and many might call me an idiot, but it is an opinion, it's mine, and you asked for it. Silicon bonds similarly to carbon, but not *quite* the same. As far as we know, there is no silicate life on earth, but that doesn't mean that it isn't there or isn't somewhere else in the Galaxy.

The only thing I can say with absolute certainty is that if no one tries, if no one thinks "impossible" things, if no one says, "I wonder what will happen if I...", then we definitely will never find out that it's impossible for a biological entity to take us on that cruise to Jupiter that we might enjoy some day.

Good luck.

Scott Kniffin
Senior Engineer, Orbital Sciences Corporation
NASA Goddard Space Flight Center
Office of Systems Safety and Mission Assurance
Radiation Effects and Analysis Group, Code 562


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