Rain fell across part of the Atacama Desert in 2015 and again in 2017 after roughly five centuries without it, but instead of reviving the driest place on Earth, it wiped out as much as 87 percent of the microbial species living there

Alberto Fairén, a co-author of a study investigating this, put the expectation plainly: “When the rains came to the Atacama, we were hoping for majestic blooms and deserts springing to life.” These organisms were highly specialized for one of the driest environments on Earth, and that specialization came with a vulnerability: a sudden flood of water could be lethal. The team also raises a practical caution: adding water to test soil for life, the way the 1970s Viking landers did, might be exactly the wrong move if the life you are hunting for is adapted to almost none of it.