Near-indestructible eight-legged creatures may now be living on the moon, and humans are to blame.
An Israeli spacecraft that crashed into the lunar surface in April was carrying thousands of tardigrades, of one Earth's most resilient animals that are known to be able to survive in outer space.
"We believe the chances of survival for the tardigrades... are extremely high," said Nova Spivack, head of the Arch Mission Foundation, which launched the first privately funded mission to the moon earlier this year.
Its lander, named Beresheet, suffered technical problems on its descent and slammed into the ground at over 500km/h.
But this wouldn't be enough to kill the dehydrated tardigrades on board. Tardigrades, also known as water bears, are tiny - most less than 1mm long - and able to survive not just outer space, but temperatures below -200C and above 150C, levels of pressure six times more than what you'd find at the bottom of the ocean and levels of radiation that would fry similar species.
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"Tardigrades can survive pressures that are comparable to those created when asteroids strike Earth, so a small crash like this is nothing to them," tardigrade expert Lukasz Kaczmarek told the Guardian.
When dehydrated, tardigrades enter a state known as cryptobiosis and can last a long time without the need for water or any other sustenance. When they're reintroduced to water, they can resume their lives as if nothing happened - even if they've been in stasis for decades.
There is water on the moon, raising the possibility the otherwise dead surface is now home to a species that's been stuck on Earth for 540 million years.
"I don't think anybody would have got permission to distribute dehydrated tardigrades over the surface of the moon, so it's not a good thing," Open University professor of planetary and space sciences Monica Grady told BBC News.
Tardigrades' ability to survive in space was a key plot point of Star Trek: Discovery's first season. They were on board Beresheet as part of a 'Noah's Ark' of Earth life, which included millions of pages of Earth history.
"We chose them because they are special," Spivack told CNN. "They are the toughest form of life we know of. They can survive practically any planetary cataclysm."
Kaczmarek said if they weren't in their dormant state, the crash would have killed them. And even if they were, they won't be able to colonise the moon because "there is no atmosphere and no liquid water".
"But it could be possible to bring them back to Earth and then add the water. They should resurrect."
A study published in 2017 found the only thing that would kill the species off would be if the world's oceans were boiled away. The only way that could happen is if there was an asteroid impact far, far bigger than the one which killed off the dinosaurs, a nearby supernova explosion or the Earth was hit by a gamma ray.
Failing that, tardigrades are expected to still be kicking when the sun dies in 5 billion years or so.
Newshub.
