Humans need water to live, so do any other organisms on this planet, even the tiniest microbes. Therefore one would expect the least to find life in very dry places. In order to find out what the limits are here in Antarctica, we went to a so called “dry valley”. As the name suggests a place without liquid water, like a desert. Dry valleys develop on permeable rock, which doesn’t hold surface water.

More famous dry valleys can be found near the American McMurdo station in Antarctica with extremely low humidity and a lack of snow and ice cover. They form due to katabatic winds, which occur when cold, dense air is pulled down the mountains. Because of their high speed (up to 300 km/h), they heat up and evaporate all the water. The dry valley here, which is about 25 km away from the station, is smaller compared to McMurdo and had some snow cover. Nevertheless, it is a very hostile place for life.

Dry valleys are considered to be the closest of any environment on Earth to the planet Mars. Therefore they are a fascinating place to test the limits of life and at what extreme conditions some life forms are still capable to survive.

The most pleasant place for a microbe in a dry valley is likely in the interior of a rock. These microbes are calledendoliths (endo=inside, lith=rock). One needs to break open the rocks using a geology rock hammer to find the green microbial bands. The green colour is derived from the chlorophyll, which the microbes use to do photosynthesis, just as plants do. The endoliths usually live just a few mm beneath the surface of a rock to catch enough sunlight to produce energy, but with enough rock cover to be protected from the harsh conditions outside the rock. They managed to figure out just the perfect spot.

Whereas the green colour makes it easy to spot the microbes in the rocks, it is impossible to see microbes in the soil by eye. Whether there are any that can cope with the extreme conditions, we will only find out once we get back to our labs…