Peter Crockford in Singularity Hub:
All organisms are made of living cells. While it is difficult to pinpoint exactly when the first cells came to exist, geologists’ best estimates suggest at least as early as 3.8 billion years ago. But how much life has inhabited this planet since the first cell on Earth? And how much life will ever exist on Earth? In our new study, published in Current Biology, my colleagues from the Weizmann Institute of Science and Smith College and I took aim at these big questions.
Carbon on Earth
Every year, about 200 billion tons of carbon is taken up through what is known as primary production. During primary production, inorganic carbon—such as carbon dioxide in the atmosphere and bicarbonate in the ocean—is used for energy and to build the organic molecules life needs.
Today, the most notable contributor to this effort is oxygenic photosynthesis, where sunlight and water are key ingredients. However, deciphering past rates of primary production has been a challenging task. In lieu of a time machine, scientists like myself rely on clues left in ancient sedimentary rocks to reconstruct past environments. In the case of primary production, the isotopic composition of oxygen in the form of sulfate in ancient salt deposits allows for such estimates to be made. In our study, we compiled all previous estimates of ancient primary production derived through the method above, as well as many others. The outcome of this productivity census was that we were able to estimate that 100 quintillion (or 100 billion billion) tons of carbon have been through primary production since the origin of life. Big numbers like this are difficult to picture; 100 quintillion tons of carbon is about 100 times the amount of carbon contained within the Earth, a pretty impressive feat for Earth’s primary producers.
More here.