Kurzgesagt – In a Nutshell
We refer mainly to two habitats, the deep oceanic subsurface (500m - 5,000m deep) and the deep continental subsurface (8m - 5,000m deep). That means, 4 x 10 29 + 3 x 10 29 bacteria and archaea may live in these habitats (= 700 octillion).
Keep in mind that the numbers can have a very wide range. There are different approaches to this question. In the source we mention below, you will find further sources for estimating these figures.
#Flemming, H.C. & Wuertz, S. (2019): Bacteria and archaea on Earth and their abundance in biofilms. Nature Reviews Microbiology, Vol. 17
We have to simplify a lot in this script. The structure of the earth is very different, e.g. there are different rocks or different interaction processes (such as groundwater) with the world on the surface. The following picture gives a rough overview of various environmental conditions and exchange processes. In addition, many living creatures have hardly been researched and accordingly many processes, e.g. how they can feed and survive, are still very vague.
Its volume is at least twice as large as all the Earth’s oceans, home to more microbes than on the rest of the entire planet combined.
