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Claim check

Can tardigrades survive in space?

Mostly supported

The core is right; the usual phrasing overstates part of it.

Dried into the tun state first, and shielded from sunlight, they survived ten days of vacuum well. Under unfiltered solar ultraviolet nearly all of them died — and an active tardigrade in vacuum dies at once.

The claim as it circulates

“Tardigrades were sent into space, exposed to the vacuum, and survived.”

Where you may have met it: Coverage of the 2007 orbital exposure experiment; Panspermia discussion, where it is offered as evidence life could travel between planets; Science communication about extreme survival generally

Taking it apart

What was claimed
That tardigrades survive exposure to space, usually stated without reference to their state or to what killed the ones that died.
What was actually observed
Desiccated tardigrades were flown for ten days in low Earth orbit under separated conditions: vacuum alone, vacuum with filtered ultraviolet, and vacuum with the full solar ultraviolet spectrum. Ground controls were held desiccated. Survival of vacuum alone was high and close to controls. Full-spectrum solar ultraviolet reduced survival drastically, with only a small proportion of one species recovering. Some survivors reproduced afterwards.
What the evidence supports
That an anhydrobiotic tardigrade tolerates vacuum — genuinely remarkable, since vacuum boils water out of ordinary tissue — and that the limiting factor in orbit is ultraviolet radiation rather than vacuum or cold.
What it does not support
Survival of space by tardigrades as such. The animals were desiccated first, which is a precondition rather than a detail: an active tardigrade in vacuum dies immediately. Nearly all of the unshielded animals died. And ten days in low Earth orbit is not interstellar space, where the radiation environment is substantially different.

The design deserves credit, because it is what makes the result informative. Space delivers vacuum, cold and unfiltered sunlight together, and an experiment applying all three at once could only report whether the animals lived. This one separated them — and found that the thing everybody assumes is lethal was nearly survivable, while the thing nobody mentions did the killing.

The panspermia use of this result is the least supportable part. If ten days of sunlight at Earth's distance kills nearly all of them, a journey between planets — which is orders of magnitude longer — is not something this experiment supports. It argues the other way.

The claims underneath

Each one carries its own evidence, scope and caveats. Expand any of them to reach the studies.

They survived orbit dried out and shielded from sunlight — and most still died

Well supported

Good evidence backs this, though some details remain open.

Desiccated tardigrades flown for ten days in low Earth orbit survived exposure to vacuum at rates comparable to ground controls held in the same desiccated state. Exposure to vacuum combined with full-spectrum solar ultraviolet radiation reduced survival drastically, with only a small proportion of one species recovering. Some survivors subsequently reproduced. Animals were desiccated before flight; active tardigrades were not tested and would not survive vacuum.

Who this applies to
two species, desiccated, for ten days in low Earth orbit
Studied in
Richtersius coronifer, Milnesium tardigradum

You may have heard

“Tardigrades can survive in space”

True with the conditions restored. The animals were dried into the tun state first — an active tardigrade in vacuum dies at once. Vacuum alone turned out to be nearly survivable, which is genuinely remarkable. Unfiltered sunlight was what killed them, and it killed nearly all of them. Radiation tolerance is also probably not an adaptation to radiation, which tardigrades never meet in quantity; it looks like a side effect of machinery for surviving drying, which damages DNA in similar ways.

Why we rate it this way, and what the caveats are
Well supportedHigh confidence

A controlled orbital experiment with matched ground controls and separated exposure conditions, so the contribution of vacuum and of ultraviolet can be told apart.

Caveats

  • Only desiccated animals were tested; the tun state is a precondition rather than a detail.
  • Ten days in low Earth orbit is not interstellar space, and the radiation environment differs substantially.
  • Survival under full solar ultraviolet was very low, which the popular summary omits.

Still unanswered

  • Is radiation tolerance in tardigrades an incidental consequence of desiccation tolerance, given that they never encounter significant radiation in nature?

Last reviewed 2026-08-11

The evidence (2 studies)

Go deeper

Tardigrade

It survives the vacuum of space by turning into glass — and dies at the temperature of a warm bath when it is awake.

Last reviewed 2026-08-11