Antarctic Lake May Reveal How Life First Began on Planet Earth

An Antarctic lake may tell researchers a bit more about Earth's ancient past. They've found an oasis of oxygen at the bottom of the lake, which may reflect conditions on Earth two and a half billion years ago before oxygen became commonplace.

The switch from a planet with very little available oxygen to one with an atmosphere much like today's was one of the major events in Earth's history. However, how this occurred has long been debated. The current idea is that it was because some bacteria evolved the ability to photosynthesize, and created enough oxygen so that by about 2.4 billion years ago, oxygen was present all the way to the upper atmosphere.

But what occurred in between and how long was the Great Oxidation Event? Scientists have speculated that there may have been "oxygen oases," which are local areas where it was abundant before it became widespread around the planet.

Now, the latest findings seem to support this theory. The researchers had been studying life in ice-covered lakes for several years, since the microbes that survive in these remote and harsh environments may be similar to some of the first forms of life on Earth.

In this case, the researchers were diving in Lake Fryxell, where they expected to find anoxic conditions. Surprisingly, though, they found some bright green bacteria at depth that looked as if it could be photosynthesizing. After they took measurements, they found a thin layer of oxygen just one or two millimeters thick being generated by bacteria.

The researchers believe that something similar could have happened billions of years ago. While lakes and rivers were anoxic, there was light available and pockets of oxygen could have accumulated in photosynthetic mats.

The findings could reveal a bit more about early Earth, and may just tell scientists what conditions were like in our planet's distant past.

The findings are published in the journal Geology.

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