Tardigrades, the nearly indestructible microscopic “water bears” that can survive the vacuum of outer space, may not be so indestructible after all. Thousands of the water bears were packed onto Beresheet, a private Israeli spacecraft that crash-landed on the moon in April. The lander spilled its payload—which included human blood and hair samples—across the moon’s surface, Wired reports. Now, leaders of the failed mission say they don’t know whether the invincible animals or the human samples survived. But the bears won’t be taking over the moon anytime soon, they say, because the atmosphere there is too dry to rehydrate the dormant creatures. As for the hair and blood, it will coexist with bags of human feces that Apollo astronauts left there—until someone returns to claim them.