In 2021, something weird was happening deep beneath Yellowstone National Park. First, a swarm of over 2,000 small earthquakes shook the area. At the same time, scientists at the park were studying bacteria that live hundreds of feet below ground. How did those bacteria react to the earthquakes? Weirdly, their population skyrocketed! But why? What could possibly connect bacteria and earthquakes?
It turns out that the earthquakes unlocked fresh energy sources for the bacteria. When earthquakes crack open rocks, water can reach new areas of minerals. Chemical reactions between certain rocks and water produce hydrogen gas, which these microbes use as an energy source. More earthquakes = greater food availability, so the population exploded!
Learning about this underground ecosystem made me wonder...is there anywhere on Earth where you can't find life? 🤔
We know bacteria can live in extreme acidity, temperature, or pressure. Microbes found deep underground, like the ones measured in Yellowstone, never see the light of day. But could there also be bacteria that never touch solid ground?
Almost! In fact, there are so many microbes that float around in the atmosphere, they have a name: aeroplankton. These life forms, which include bacteria, algae, mosses, viruses, and fungi, usually start off on the ground or in the ocean. Crashing ocean waves spray microbes into the air. Forest fire updrafts pull microbes out from soil or tree bark and swirl them into the atmosphere. Even a good gust of wind will send microscopic life flying into the clouds. Once they're up, it only takes a puff to stop these tiny organisms from falling back to the ground.💨
When aeroplankton are sent flying, their lives are very different from their relatives on the ground. In some ways, their survival gets easier, because there is less competition for resources in the air. However, they also face new risks, like floating so high that they reach damaging UV rays and intense radiation.
How high can these microbes go? Scientists use weather balloons, airplanes, drones, and mountaintop weather stations to study aeroplankton. Using these tools, scientists have measured fungal spores 12 miles above the Pacific Ocean! 😱
Does is matter that microorganisms are floating around in the sky? Yes! Scientists think that aeroplankton play an important role in the weather. They act as nucleation points for clouds. Water molecules in the sky are too small to stick together on their own. They need something a little bigger to stick to! Water in the atmosphere collects around tiny bits of dust, sand, and - you guessed it! - aeroplankton to form clouds.
Of course, many aeroplankton eventually fall from the sky. The graph below shows the number of different types of bacteria that fall in Korea with precipitation (wet) and without precipitation (dry) for several months of the year:
If I brought this graph into the classroom, here are some questions I'd have to go with it:
💡According to the graph, during which months did more types of bacteria fall during dry conditions than wet conditions?
💡When did the greatest number of bacteria types fall from the atmosphere during the months shown?
💡From this graph, can you determine which month of the whole year had the greatest number of individual organisms falling from the sky? Why or why not?