A new study is providing insight into the ecology of unusually large microfossils found in 3.0–3.4 billion year old (early Archaean) sediments from both Western Australia and South Africa. These objects could be ancient artefacts of life, and are known as lenticular microfossils.

The results of the study support the idea that if the microfossils are evidence of life, the organisms that they represent could have been planktonic. Plankton refers to small organisms that float and drift in salt or fresh water. On Earth today, planktons include a wide range of organisms, from eukaryotes to cyanobacteria, and make up the base of the food chain in aquatic systems.

The researchers simulated fluid dynamics with virtual cells in order to explain why these Archean microfossils have such a unique morphology and unusually large size. They believe that features like increased cell size may have ultimately helped to slow the sedimentation rate of the organisms in water.

The study, “Early Archean planktonic mode of life: Implications from fluid dynamics of lenticular microfossils,” was published in the journal Geobiology. The work was supported by NASA Astrobiology through the Exobiology Program.