Facts About Tardigrades in Space

Tardigrades are microscopic animals, typically measuring between about 0.1 and 1.2 millimeters long, with most adults around 0.5 millimeters.

They live almost everywhere on Earth, including soil, leaf litter, mosses, and both freshwater and marine environments.

Tardigrades make up their own animal phylum, Tardigrada, which includes over 1,300 known species.

As extremophiles, tardigrades can survive temperatures as low as roughly -328°F (-200°C) and as high as about 300°F (150°C) when in a dormant state, far beyond what active tardigrades could withstand.

They can endure pressures several times greater than those found in the deepest ocean trenches, roughly comparable to being compressed under thousands of atmospheres.

Tardigrades can withstand radiation doses roughly a thousand times higher than the dose that would be lethal to a human.

Their survival secret is a state called cryptobiosis, a suspended-animation-like condition triggered by extreme dehydration or other environmental stress.

In cryptobiosis, tardigrades can lose the vast majority of their body water, curling into a dried-up form called a "tun."

Their metabolism can drop to a tiny fraction of normal activity, sometimes estimated at well under 1%, letting them conserve energy for years.

Tardigrades produce protective proteins and sugars, including trehalose in some species, that help stabilize their cells and DNA during dehydration.

In September 2007, tardigrades became the first animals known to survive direct exposure to the vacuum and radiation of outer space, during the European Space Agency's FOTON-M3 mission.

On that mission, dehydrated tardigrades were carried outside the spacecraft in orbit for about 10 days, exposed to space vacuum and solar UV radiation.

After returning to Earth and being rehydrated, many of the tardigrades revived, and some went on to reproduce normally.

Tardigrades surviving spaceflight strengthened interest in astrobiology, since it shows that some Earth life can endure conditions similar to those found on other worlds.

Scientists study tardigrade survival mechanisms for potential insights into preserving human cells, tissues, and even vaccines without refrigeration.

In April 2019, the Israeli Beresheet lunar lander crashed on the Moon while carrying a digital "Lunar Library" that included thousands of dehydrated tardigrades embedded in resin.

It is not confirmed whether any tardigrades survived the Beresheet crash; the lander itself was destroyed on impact, and no evidence of surviving tardigrades has been verified.

The incident sparked debate among scientists and ethicists about planetary protection and the risks of unintentionally introducing Earth organisms to other celestial bodies.