Weird and wonderful creatures thrive in the planet’s most hostile places, but there are a few spots too harsh for even the hardiest.
In the Atacama Desert in northern Chile, it looks as if nothing could ever survive. It is one of the driest places in the world, and some sections of the Mars-like expanse can go 50 years without feeling a drop of rain. As poet Alonso de Ercilla put it in 1569: “Towards Atacama, near the deserted coast, you see a land without men, where there is not a bird, not a beast, nor a tree, nor any vegetation.”
Yet Atacama is not devoid of life. Microorganisms called endoliths have found a way to cling on, by hiding themselves inside the pores of rocks, where there’s just enough water to survive. “They support a whole community of organisms that eat the byproducts of their metabolism,” says Jocelyne DiRuggiero, a microbiologist at Johns Hopkins University. “And they’re all just sitting right there in the rocks – it’s quite fascinating.”
Life, it seems, has an incredible knack for finding ways to persist. Indeed, microorganisms have been around for nearly four billion years, giving them ample time to adapt to some of the most extreme conditions in the natural world. But are there places left on Earth so harsh that they are rendered sterile?
Heat is a good starting point for answering this question. The record for heat tolerance is currently held by a group of organisms called hyperthermophile methanogens, which thrive around the edges of hydrothermal vents in the deep sea. Some of these organisms can grow at temperatures of up to 122C (252F).
Most researchers believe that around 150C (302F) is the theoretical cut-off point for life, however. At that temperature proteins fall apart and chemical reactions cannot occur – a quirk of the biochemistry that life on Earth (so far as we know) abides by. This means that microorganisms can thrive around hydrothermal vents, but not directly within them, where temperatures can reach up to 464C (867F). The same is true for the interior of an active volcano on land. “I really think temperature is the most hostile parameter,” says Helena Santos, a microbial physiologist at the New University of Lisbon and president of the International Society for Extremophiles. When things get hot enough, she says, “It’s impossible – everything is destroyed.”