Can any animal survive the vacuum of space without a suit?

Space is about the least friendly place imaginable. There is no air, the temperature swings wildly, and unfiltered sunlight is packed with ultraviolet radiation that shreds living cells. Astronauts need suits costing millions just to step outside. Yet one animal has been sent into open space with no protection at all, and plenty of them came back alive.

The short answer

Tardigrades, tiny animals nicknamed water bears, survived ten days exposed to open space in 2007. Most handled the vacuum with no obvious harm. Some even survived the full blast of solar ultraviolet radiation, and survivors went on to reproduce normally.

The real story

Tardigrades are tiny invertebrates, roughly 0.1 to 1.5 millimetres long, that look a bit like chubby vacuum-cleaner bags with claws. Their party trick is drying out. They can survive in a shrivelled, dried state called cryptobiosis, with their body processes almost stopped. Add water later and they can wake up again.

In September 2007 a team led by Ingemar Jönsson of Kristianstad University in Sweden and Ralph Schill of the University of Stuttgart sent dried tardigrades into orbit on the FOTON-M3 mission, inside a European Space Agency experiment container called BIOPAN-6. At about 270 kilometres up, the lid opened and the animals sat in the raw environment of space for ten days. Two species flew: Richtersius coronifer and Milnesium tardigradum.

The results, published in Current Biology in 2008, were striking. Animals exposed to the vacuum alone survived about as well as the ones left on Earth. Those also hit with some ultraviolet light did reasonably well too. The full dose of solar radiation was much harsher: survival dropped sharply, but a small number of Milnesium, over 2%, still came back to life. The researchers said this was the first time any animal had been tested in open space conditions.

It is worth being precise. They survived in their dried, dormant state. Nobody has seen an active tardigrade wandering around in a vacuum, and they did not reproduce in space. But surviving the trip at all was something no other animal had shown.

Why people get it wrong

We judge space by what it would do to us, and to us it would be fatal in moments. Science fiction backs that up with plenty of dramatic airlock scenes. It is natural to assume nothing alive could cope.

Tardigrades are also so small that most people have never heard of them. They do not fit our picture of a tough creature. We imagine sharks, cockroaches or rats, not a microscopic animal that looks like a toy. Being tiny and able to switch life almost off turns out to be a far better survival kit than size or teeth.

“Ten days in space, then home for a drink of water. Honestly, sounds like a decent holiday.”