Analyzing fossils can be quite challenging, especially when they are so tiny that a microscope is required to see them. A team of researchers has now devised a new method to tackle this issue.
Fossils are not always large like those of dinosaurs; some fall into the category of microfossils, which are so small that they can only be examined under a microscope. These tiny fossils provide crucial insights into how early life forms developed important traits, enhancing our understanding of the evolution of life. A research team headed by Akizumi Ishida from Tohoku University, in partnership with specialists from the University of Tokyo and Kochi University, has created an innovative method for studying these microfossils.
According to Ishida, “In order to study microfossils, scientists need to identify tiny amounts of essential elements like phosphorus and molybdenum, but this has previously proven to be quite challenging.”
The researchers are concentrating on Gunflint microfossils that are 1.9 billion years old, recognized as a benchmark in microfossil research. They utilized an original approach by adhering these microfossils onto a specially treated glass slide known as ITO-glass, which allowed them to use both optical and electron microscopy for thorough observations.
ITO-glass is a glass surface coated with a thin layer of indium tin oxide (ITO). This conductive metal oxide coating is ideal for both electron microscopy and secondary ion mass spectrometry (SIMS), while also permitting optical viewing. Its transparency allows scientists to inspect the internal structures of microfossils effectively.
This new approach made it possible to accurately identify trace elements within the microfossils. In other words, it could distinguish the actual quantities of elements from the background levels of interference. For instance, phosphorus can naturally occur in sedimentary rocks, making it crucial to differentiate between the two sources.
By mitigating the interference caused by elements from surrounding rocks and materials used for mounting the fossils, the researchers accurately detected incredibly low concentrations of phosphorus and molybdenum using a device called NanoSIMS (High Spatial Resolution Secondary Ion Mass Spectrometer). This instrument can image nearly all elements, excluding noble gases, with ultra-high precision of less than one micron.
Their examination of phosphorus along the edges of the microfossils indicated that these ancient microorganisms had phospholipid cell membranes similar to those seen in contemporary organisms. Furthermore, the detection of molybdenum within the bodies of these microfossils hinted at the presence of potential nitrogen-fixing metabolic enzymes, aligning with prior findings that classified these microfossils as cyanobacteria.
This groundbreaking procedure is distinctive for its ability to yield consistent observations and analyses from the same sample. It represents a significant leap in understanding the evolution of life on Earth, providing direct evidence of cellular membranes and metabolic activities in ancient microorganisms.
The method can be leveraged not just for microfossils but also for geological samples from early Earth featuring limited organic content. This opens possibilities for investigating even older geological eras. Additionally, it encompasses trace elements like copper, nickel, and cobalt, which can expose metabolic trends. These discoveries are anticipated to establish new benchmarks in early life evolution studies and contribute to resolving profound inquiries about the origins and development of life on Earth.
