A bacteria that extracts water from rocks! - A 2020 Cool Paper

Life needs water. That’s why the rain forest has more living things than the desert. But even in extremely dry deserts, organisms have adapted to get water in the most unusual of ways. This cool paper is about a type of bacteria that can extract water from rocks. The bacteria live in the Atacama Desert. It’s one of the driest places on earth. It can go years without any rainfall. In fact, it’s so dry that NASA scientists go there to test Rovers they plan to send to Mars! The bacteria that live in this desert are a type of cyanobacteria. They can do photosynthesis and they live inside rocks and little cracks and holes.

00:43 - And the scientists who published this paper wondered, “How do the bacteria get enough water to survive?” The bacteria live on a type of rock called gypsum. And we use gypsum to make drywall. You’re probably surrounded by some of it right now. Now gypsum is really interesting because it has water in it. And I don’t mean little pockets of water inside the rock. I mean the rock itself has water molecules in it. Rocks are made out of crystals. Mineral crystals. Think salt – It’s a crystal made of sodium and chloride. But gypsum crystals are made out of calcium sulfate and water molecules. And in fact, if you remove the water molecules from gypsum, you get a different kind of crystal called anhydrite. So the scientists are thinking, “The bacteria live on a type of rock that has water molecules in it. Maybe that’s where the bacteria get the water they need!” But if that were true then you’d expect the rock underneath the bacteria to have all the water molecules extracted from it.

So it should be in the water free anhydrite form, rather than 01:42 - in the gypsum form. To test that hypothesis the researchers took rocks from the Atacama Desert and they tested them using a technique called x-ray diffraction. Different peaks on this plot indicate different states of the rock. A peak here shows the rock is in the water-free version anhydrite. And, consistent with their hypothesis, rocks that had bacteria had more anhydrite – more water extracted – than rocks without bacteria.

02:08 - But to test whether the bacteria actually extract water from the rocks and convert gypsum into anhydrite, they went to the lab. They took pure gypsum rocks and they added bacteria to them. And to some samples they added water because you’d only expect the bacteria to go to great lengths to extract the water from the rocks if they really needed it. And in fact that’s exactly what they saw. Only when the rocks were dry and only when they had bacteria on them was water extracted and the gypsum was converted into anhydrite. Extracting water from rocks is a strategy for surviving in extremely dry environments like Mars. Maybe there’s life in the rocks there.

We’ll have to wait for those rover’s to 02:46 - find out!.