Tardigrade

The tardigrade, also called the water bear or moss piglet, is a tiny eight-legged animal usually around half a millimetre long. It is one of the toughest animals known. Tardigrades have survived being frozen to near absolute zero, heated well above boiling for a short time, blasted with radiation and, in a 2007 experiment, exposed to the vacuum of open space.^[1] They live in moss.

It is the only animal that could survive almost anything and has chosen to spend the time in a damp patch on a wall.

How it survives

When conditions get bad, a tardigrade dries out, pulls in its legs and curls into a tiny dried-up ball called a tun. In this state its body almost stops working. Add water, sometimes years later, and it can uncurl and carry on.^[2] Biologists describe this as the closest thing in nature to being put on hold.

A tardigrade in a tun can wait out conditions that would finish off almost anything else. Most of the time, though, the bad conditions it is waiting out are a puddle drying up.

Space

Some of the tardigrades sent into space in 2007 survived the trip and went on to lay eggs. In 2019 a lunar lander carrying dried tardigrades crash-landed on the Moon. Whether they survived the landing is unknown, and nobody has gone to check, since the tardigrades are not expected to be in a hurry.

See also

• Moon – where some may still be
• Puddle – its usual crisis
• Frost – nothing to a tardigrade

References

1. Moss, M. (2008). Toughest in the Puddle. Lichen Press.
2. Tun, T. (1999). “On Hold: Dried Animals”. Journal of Waiting 0: 0.
3. Orbit Committee (2007). “They Came Back”. Brief report.