Investigating the potential for pseudofossil formation in Earth's ancient sediments.
[sciencythoughts.blogspot.com]
The earliest evidence for life on Earth comes in two forms; chemical evidence, i.e. compounds believed to have been derived from the activities of living organisms and isotopic signals thought to be indicative of biological activity, and through the presence of structures believed to be microfossils in ancient sedimentary deposits. In both cases, identifying these with confidence requires considerable skill, as there remains a danger that abiotic processes might have achieved the same results. One of these dangers is the potential formation of pseudofossils (structures which resemble fossils but are of non-biological origin). The most ancient structures interpreted as being microfossils take two forms, microbial filamentous and spherical cells, but structures morphologically similar to both of these have been synthesised on the lab by non-biological means, raising the possibility that none of these ancient 'fossils' are actually of biological origin. The researchers were able to recreate these strucutures, also known as organic biomorphs, by oxidising sulphides in the presence of organic materials, under which circumstances they formed spontaneously. This has been shown to be possible under a wide range of conditions likely to have been present on the ancient Earth, and with a wide range of organic compounds serving as precursors.