Diverse microbial life existed on Earth at least 3.75 billion years ago, suggests a new study led by UCL scientists that challenges the conventional view of when life began.
For the study, published in The progress of science, the research team analyzed a stone the size of a fist from Quebec, Canada, estimated to be between 3.75 and 4.28 billion years old. In a former Nature paper, the team found small filaments, buds and tubes in the rock, which appeared to be made of bacteria.
However, not all scientists agreed that these structures – dating about 300 million years earlier than what is more commonly accepted as the first sign of ancient life – were of biological origin.
Now, after extensive further analysis of the rock, the team has discovered a much larger and more complex structure – a stem with parallel branches on one side that is almost an inch long – as well as hundreds of distorted spheres or ellipsoids next to tubes and filaments .
The researchers say that while some of the structures may have been created through random chemical reactions, the “tree-like” stem with parallel branches was most likely of biological origin, as no structure created via chemistry alone has been found similar to it.
The team also provides evidence of how the bacteria got their energy in different ways. They found mineralized chemical by-products in the rock, which are consistent with old microbes that feed on iron, sulfur and possibly also carbon dioxide and light through a form of photosynthesis that does not involve oxygen.
These new findings suggest, according to scientists, that a variety of microbial lives may have existed on the original Earth, potentially as little as 300 million years after the planet’s formation.
Main author Dr. Dominic Papineau (UCL Earth Sciences, UCL London Center for Nanotechnology, Center for Planetary Sciences and China University of Geosciences) said: “Using many different lines of evidence, our study strongly suggests that a number of different types of bacteria existed on Earth for between 3.75 and 4.28 billion years ago. ”
“This means that life could have begun as little as 300 million years after the Earth was formed. In geological terms, this is fast – about a spin of the Sun around the galaxy.”
“These findings have implications for the possibility of extraterrestrial life. If life is relatively quick to emerge, given the right conditions, this increases the chance that life exists on other planets.”
For the study, the researchers examined rocks from Quebec’s Nuvvuagittuq Supracrustal Belt (NSB), which Dr. Papineau collected in 2008. NSB, once part of the ocean floor, contains some of the oldest sedimentary rocks known on Earth, believed to have been laid down. near a system of hydrothermal vents, where cracks on the seabed escape through iron-rich water heated by magma.
The research team cut the rock into sections about as thick as paper (100 microns) to closely observe the tiny fossil-like structures made of hematite, a form of iron oxide or rust, and encapsulated in quartz. These cutting discs, cut with a diamond-coated saw, were more than twice as thick as previous sections that the researchers had cut, allowing the team to see larger hematite structures in them.
They compared the structures and compositions with newer fossils as well as with iron-oxidizing bacteria located near hydrothermal vents today. They found modern equivalents to the twisted filaments, parallel branched structures, and distorted spheres (irregular ellipsoids), for example, near the Loihi submarine volcano near Hawaii, as well as other vent systems in the Arctic and Indian Oceans.
In addition to analyzing the sample samples under various optical and Raman microscopes (which measure the scattering of light), the research team also digitally recreated sections of the clip using a supercomputer that processed thousands of images from two high-resolution image processing techniques. The first technique was micro-CT or microtomography, which uses X-rays to look at the hematite inside the rocks. The other was focused ion beam, which shaves off small-200 nanometer-thick cutting discs, with an integrated electron microscope that takes a picture between each disc.
Both techniques produced stacks of images that were used to create 3-D models of different sizes. The 3-D models then allowed the researchers to confirm that the hematite filaments were wavy and twisted and contained organic carbon, which are properties shared with today’s iron-eating microbes.
In their analysis, the team concluded that the hematite structures could not have been created through compression and warming of the rock (metamorphosis) over billions of years, and pointed out that the structures appeared to be better preserved in finer quartz (less affected by metamorphosis)) than in the coarser quartz (which has undergone more metamorphosis).
The researchers also looked at the levels of rare earth elements in the fossil-laden rock and found that they had the same levels as other ancient rock samples. This confirmed that the seabed deposits were as old as the surrounding volcanic rocks, and not younger deceptive infiltrations, as some have suggested.
Prior to this discovery, the oldest fossils previously reported were found in Western Australia and dated to 3.46 billion years old, although some scientists have also disputed their status as fossils, claiming that they are of non-biological origin. .
4 billion years: The world’s oldest fossils excavated
Dominic Papineau, Metabolically diverse primordial microbial communities in Earth’s oldest seabed hydrothermal jasper, The progress of science (2022). DOI: 10.1126 / sciadv.abm2296. www.science.org/doi/10.1126/sciadv.abm2296
Matthew S. Dodd et al., Evidence of early life in the Earth’s oldest hydrothermal vents, Nature (2017). DOI: 10.1038 / nature21377
Provided by University College London
Citation: Different life forms may have evolved earlier than previously thought (2022, April 13) retrieved April 14, 2022 from https://phys.org/news/2022-04-diverse-life-evolved-earlier-previously.html
This document is subject to copyright. Except for any reasonable trade for the purpose of private investigation or research, no part may be reproduced without written permission. The content is provided for informational purposes only.