Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Spacesuits optional for 'water bears'

Tiny invertebrates are the first animals to withstand the vacuum and radiation of space.

The humble water bear has gone where no animal has gone before. Credit: STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY

It's one small step for water bears, one giant leap for animal-kind. Tiny animals called tardigrades — better known as water-bears — have become the first animals to survive the cruel vacuum, intense cold and radiation of space without a spacesuit.

Water bears were already known to be among the toughest critters alive. When not flying in a low Earth orbit, they prefer to spend their days in water, perhaps on a beach or a dewy patch of moss. But when the water dries up, the millimetre-long 'bears' can contract into a dried-out state and survive like that for years. They are also one of the few animals that survive year-round on continental Antarctica, and are among the most radiation-resistant animals known.

So if any animal on Earth could survive the rigours of space, Ingemar Jönsson, of Kristianstad University in Sweden, and her colleagues figured it would be the water bears. They loaded two species of tardigrade — Richtersius coronifer and Milnesium tardigradum, both already in their desiccated form — onto the European Space Agency's Biopan-6 experimental platform. The experiment was launched into orbit during the unmanned Russian Foton-M3 mission in September 2007.

For ten days, the tardigrades were exposed to the radiation, vacuum and low temperature of space. R. coronifer did not fare terribly well — none survived when exposed to the full spectrum of ultraviolet radiation, which can be extremely damaging to DNA. But three specimens of M. tardigradum did.

And when some wavelengths of ultraviolet light were filtered out (those shorter than 280 nanometres or longer than 400 nanometres), eggs laid by space-faring Milnesium tardigradum hatched just as well as controls that had not been exposed to space vacuum or ultraviolet radiation. The results are published this week by Current Biology1.

Resilient life

The results demonstrate just how resilient life on Earth can be, says Catharine Conley, NASA's acting Planetary Protection Officer. Before now, only lichens and bacteria had demonstrated their ability to survive both space vacuum and cosmic radiation.

And although tardigrades were clearly resistant to desiccation on Earth, the conditions in space are much more challenging. At sea level on Earth, air pressure is about 100,000 pascals; in low Earth orbit, it is more than a billion times lower. "Such low pressure imposes an extreme dehydration on cells," says Jönsson. "Not many water molecules can remain in the body under those conditions."

Some researchers want to understand how various Earth organisms might survive interplanetary flight, as a way of gauging whether life could have spread from one planet to another. As Planetary Protection Officer, Conley's mission is to understand which organisms might hitch-hike a ride on a spacecraft and contaminate other planets.

But she isn't too worried about the likelihood that tardigrades might catch a ride to Mars and set up shop. "Tardigrades, unfortunately, need stuff to eat," says Conley. "If you had to pick a single type of organism that would be likely to colonize Mars, it'd be a lichen, or maybe a photosynthesizing bacteria."



  1. Jonsson, K. I. et al. Curr. Biol. 18, R1–R3 (2008).

    Article  Google Scholar 

Download references


Related links

Related links

Related links in Nature Research

Astronomy special

Space shuttle special

Nature Insight: Astrobiology

Related external links

Tardigrades in Space blog

NASA Planetary Protection

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Ledford, H. Spacesuits optional for 'water bears'. Nature (2008).

Download citation

  • Published:

  • DOI:


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing