In Starcraft, the biological, hive-minded Zerg can survive and even thrive in the vacuum of space, while the more fragile humans (and presumably the Protoss) require some sort of space suit. So that got me wondering: How plausible is it for living organisms to be able to withstand the vacuum, extreme temperatures and high radiation levels of space?
Fist of all, I’m going to set aside how the Zerg fly around in space. That may be the subject of a future post. I’m more concerned with just the idea of a hydralisk standing on an exposed moon-like surface and not immediately freezing or suffocating or otherwise dying gruesomely.
As you may imagine, NASA is quite interested in how living things react to space-like conditions. Between concerns over contaminating places like Mars and Europa with terrestrial microbes, and that whole “launching humans into space” business, there have actually been a lot of studies done on the topic.
Before we dive into more extreme forms of life, let’s examine what happens to a human exposed to vacuum. I want to clear up one misconception right away: You don’t pop like a balloon in space. Nor do you instantly freeze solid or pass out. It turns out that your circulatory system provides enough pressure so your blood wouldn’t boil even in zero pressure, and you remain conscious as long as the oxygen that’s already in your blood lasts (about 15 seconds). The biggest danger is holding your breath: don’t do it!
When exposed to vacuum, all the air in a person’s lungs goes rushing out in a vain attempt to fill the void. This can cause serious damage if you try to hold it in, in much the same way that a scuba diver who inhales pressurized air at depth risks fatal lung damage if she holds her breath and then swims to the surface.
You don’t instantly freeze in space because there is no effective way to lose heat! Normally we’re surrounded by air which can convect heat away, but in space the human body is not in contact with other matter, so the only way it can lose heat is by radiating it away as infrared light, which is a very inefficient process. Anyone who has ever used a thermos to keep their coffee warm knows that heat doesn’t transfer through a vacuum very well!
Of course, people still have issues when exposed to space. You can get a nasty sunburn in seconds. You can get the “bends” (another affliction of SCUBA divers, in which bubbles begin to form in the bloodstream and cause damage). There will be tissue damage. Hence the bulky space suits that NASA uses and the bulky space marine suits in Starcraft.
But the point is that even fragile creatures like humans can survive for a few tens of seconds in a pinch. But we want to talk about the Zerg: insect-like creatures that can survive intense radiation and the vacuum of space with little to no damage! How plausible could that be?
Well, let me introduce you to the tardigrade, an insect-like creature that can survive intense radiation and the vacuum of space with little to no damage! Tardigrades, also known as “water bears” are microscopic, water-dwelling, segmented and absurdly durable creatures. They are especially hardy when they are in a state of suspended animation.
According to Wikipedia:
Some can survive temperatures of -273°C (-460 °F), close to absolute zero, temperatures as high as 151 °C (303 °F), 1,000 times more radiation than other animals, and almost a decade without water. In September 2007, tardigrades were taken into low Earth orbit on the FOTON-M3 mission and for 10 days were exposed to the vacuum of space. After they were returned to Earth, it was discovered that many of them survived and laid eggs that hatched normally, making these the only animals known to be able to survive the vacuum of space.
There are also plenty of simpler creatures that can survive in extreme conditions. For example, the bacterium deinococcus radiodurans can repair its DNA on the fly, withstanding doses thousands of times higher than the lethal limit for humans. For the zerg to survive long in space, they would need to share this ability to repair radiation damage rapidly.
They would also have to be able to survive without air, and to completely exhale all the air inside them safely before entering space. One possible mechanism to help the zerg survive without air is the creep. Creep provides sustenance to zerg buildings, but if it also could nourish zerg creatures, it might keep them going without the need to breathe. Combine that with a slow metabolism, making any nourishment or oxygen absorbed from the creep last for a while after they leave it, and you might be able to do away with the need to breathe. This is admittedly far-fetched, and would work much better for microscopic creatures with higher surface area to volume ratios.
The problem with a slow metabolism is that extreme temperatures would be problematic. Although an organism doesn’t freeze or burn instantly in space, long-term exposure would still be deadly unless the organism is able to moderate its temperature by matching its metabolism to the amount of energy going in and out while it sits in space. Did you ever wonder why space suits are white? It’s to reflect sunlight! Humans already put off a lot of heat, and it’s already difficult to get rid of it in space, so NASA doesn’t want even more heat from the sun making things too toasty for the astronauts. I’m not sure I have a good way around this for the zerg. Take a look at any zerg swarm and they look pretty active, but that means a high metabolism, producing excess heat that needs to be dealt with and requiring extra calories and, presumably, oxygen which would be difficult to get in space.
Pressure is, in my mind, less of a problem. We know that the zerg have an armored carapace, and since even fragile human tissues can provide enough confining pressure to keep the fluids inside from boiling, I’m willing to believe that the Zerg could survive extreme low pressures.
The question of course, is how the Zerg could evolve in space? But luckily, we can wave our magic wand to explain this point. We’re told in the games that the zerg did not really evolve independently but were engineered by the ancient and powerful Xel’naga, combining many different species. Considering that present-day puny humans are capable of splicing genes from multiple species together to create improved organisms, I have little trouble picturing an advanced intelligence picking and choosing all the right genes to create space-hardy creatures. Maybe the zerg even have a little bit of water bear DNA in them!