They have, we are told, survived five mass extinctions:
After a month, though, Suma found the sweet spot for growing the tardigrades and began to investigate their hardiness to various environmental stressors. He and Eswarappa were particularly curious about the critters’ resistance to ultraviolet (UV) radiation. Placed under a germicidal UV lamp for 15 minutes—an exposure that would kill most microorganisms—the tardigrades came out unscathed. Curious if they could confer the UV protection to C. elegans and another species of water bear, the researchers ground up the new tardigrade to create a paste with the mystery UV-resistance substance that they could slather on the other creatures. As they were doing this, they noticed that the paste fluoresced under UV light.Ashley Yeager, “Tardigrades’ List of Super Powers Grows Ever Longer” at The Scientist
They couldn’t withstand humans grinding them up but hey… .