The TARDIS experiment compared exposure to vacuum alone with exposure to vacuum combined with solar ultraviolet radiation.
What Did the Space Experiment Show?
The TARDIS experiment exposed dried tardigrades to space conditions during the European Space Agency’s FOTON-M3 mission in September 2007. The primary study kept them in low Earth orbit for ten days, at an altitude of 258–281 km.
Researchers tested two species: Richtersius coronifer and Milnesium tardigradum. Both survived exposure to space vacuum alone, with no significant difference from the control animals. The result was therefore specific: dried tardigrades tolerated vacuum, but the experiment also tested the effects of ultraviolet radiation.
How Could the Tardigrades Withstand the Vacuum?
Tardigrades endured the vacuum in a dried, low-activity state called anhydrobiosis. In this state, they lose most of their body water and their metabolism nearly stops.
The animals contract into a shrunken form commonly called a tun. The 2008 study reported that its tardigrades tolerated residual water levels below 1% of their mass. This helps explain the conditions in which they survived, but the precise mechanisms that protect tardigrades from extreme drying and radiation were not yet known.
How Did Scientists Test Their Survival?
The TARDIS experiment compared tardigrades exposed to vacuum alone with samples exposed to vacuum plus ultraviolet radiation, as well as with laboratory controls. This let researchers distinguish the effects of vacuum from those of the added radiation.
After the flight, researchers rehydrated the animals and assessed their survival and reproduction. The comparison showed that adding solar ultraviolet radiation greatly reduced survival relative to vacuum alone. So while the animals tolerated one harsh condition, the combined exposure produced a different result.
What Does the Result Really Mean?
The 2008 study described tardigrades as the first animals shown to survive exposure to space vacuum. That finding does not mean they can withstand every condition in space: only three Milnesium tardigradum specimens survived exposure to vacuum combined with the full ultraviolet-radiation range tested.
The study found that solar radiation, rather than vacuum alone, sharply harmed survival. It tested desiccated tardigrades, so it does not show that active, hydrated tardigrades can withstand open-space conditions. The remarkable result is narrower—and more precise—than the claim that tardigrades can survive anything space throws at them.
