Scientists Made Tardigrade Bullets To Test Space Travel Water Bear Ballistics
If you were to rank animals by scale versus fascinating physical features, tardigrades – aka water bears – would probably land top of the heap. Though microscopic, the creatures' incredible resilience has made them a source of outsize interest for scientists, not to mention putting them into some deeply odd experiments.
Researchers have already shown that tardigrades can withstand extremely low temperatures close to absolute zero, and high temperatures past the point where water would boil. They can handle vacuums, too, their chunky little bodies shrugging off what would prove fatal for human astronauts.
It's not to say that scientists have now started looking to more unusual trials by which to test out tardigrade hardiness, but the segmented micro-animals are definitely a good place to start if you want to see how a particularly resilient creature might handle extremes. A team at Queen Mary University of London, in the UK, decided to see whether tardigrades could potentially survive the sort of forces that might be involved were they to be transported to – and crash-landed on – other worlds.
That's a key element of the so-called panspermia theory, in which scientists theorize that life – albeit only in tiny forms – could have been spread between planets via dramatic meteorite eruptions. Those space-faring rocks, they suggest, could have been thrown out after an asteroid strike, taking with them a cargo of creatures. If the meteorite subsequently crashes into another planet or moon, it could in effect seed that with foreign lifeforms.
Such life would be microscopic, of course – we're not talking giraffes and cats riding out a cross-galaxy trip, here – but it'd need to handle not only the extremes of space but the huge forces involved as chunks of rock break off, are spurred into motion, and then collide with other worlds. Lead researcher Alejandra Traspas decided tardigrades would be an ideal candidate for that, but no project before this had looked specifically at whether the animals could withstand the degrees of force they'd encounter on such a trip.
To figure that out, they fed a cohort of tardigrade travelers, froze them so as to put them into hibernation, and then loaded them into hollow nylon bullets. That odd ammunition was then fired from a two-stage light gas gun, ScienceMag reports, into a sand target. Whether or not the tardigrades survived, and the speeds at which they did so, gave a final estimate of just what sort of impact they could handle.
Turns out, if you want to avoid tardigrade "mush" – Traspas describes it – you need to keep it down to under around 900 meters per second, or just over 2,000 mph. Anything involving shock pressures above 1.14 gigapascals (GPa) proved fatal, too.
It puts a speed limit on the panspermia theory, because it means fast-moving asteroids and meteorites would probably kill any unwitting passengers in the process of striking a new world. On the flip side, though, there's the possibility of one day taking new samples from distant planets and moons during speedy fly-by missions, with probes scooping up water and ice as they whip past the surface or as it erupts into plumes. Get the speed right, in theory, and if there's life in those samples it could survive the sudden arrival in a spaceship test tube.