A new study has revealed that the first life on Earth appeared at least 3.75 billion years ago – about 300 million years earlier than previously thought.
Experts’ thinking is based on the analysis of a fist-sized rock from Quebec, Canada, which is estimated to be between 3.75 and 4.28 billion years old.
The researchers had previously found threads, knobs and small tubes in the rock, which appear to have been made by bacteria. However, not all scientists agreed that these structures were of biological origin.
Now, after further thorough analysis, the team at University College London has discovered a larger and more complex structure within the rock – a trunk with parallel branches on one side about a centimeter long.
They also found hundreds of deformed spheres, or “ellipses,” next to tubes and threads.
The researchers say that while some of the structures can be visualized through chemical reactions by chance, the “tree-like” trunk with parallel branches was likely biological in origin.
This is because he has never found a structure created by chemistry alone like him.
Until now, the oldest known evidence of life on Earth was a 3.46-billion-year-old rock from Western Australia that contained microfossils resembling worms.
Using many different evidence, our study strongly suggests that a number of different types of bacteria existed on Earth between 3.75 and 4.28 billion years ago, said lead author Dr. Dominic Papineau, of the University of California’s Department of Earth Sciences.
This means that life can begin 300 million years after the formation of the Earth. And geologically speaking, that’s fast – about one rotation of the Sun around the galaxy.
The team also uncovered evidence of how bacteria obtain their energy in different ways.
They found mineral chemical products in the rocks consistent with ancient microbes that lived on iron, sulfur, and possibly also carbon dioxide and light through a form of photosynthesis that didn’t include oxygen.
It also has implications for the possibility of extraterrestrial life.
“If life is relatively quick to emerge, under the right conditions, this increases the chance of life being found on other planets,” Dr. Papineau said.
For the study, the researchers examined rocks from the Nuvvuagittuq Supracrustal Belt in Quebec (NSB), which Dr. Papineau collected in 2008.
Once part of the sea floor, the NSB contained some of the oldest known sedimentary rocks on Earth, which are believed to have been laid near a hydrothermal vent system, where cracks in the sea floor allow passage through iron-rich waters heated by magma.
The research team cut the rock into paper-thick sections (100 microns) in order to closely observe the tiny fossil-like structures, which consist of hematite, a form of iron oxide or rust, and coated with quartz.
These slices of rock, cut with a diamond-encrusted saw, were more than twice as thick as the previous bits the researchers cut, allowing the team to see larger structures of hematite in them.
They compared the structures and structures to more recent fossils, as well as to iron-oxidizing bacteria found near today’s hydrothermal vent systems.
This allowed them to identify modern-day equivalents of twisted filaments, parallel branching structures, and deformed spheres (irregular ellipsoids), for example near the undersea Loihi volcano in Hawaii, as well as other venting systems in the Arctic and Indian Oceans.
In addition to analyzing the rock samples under various optical microscopes and Raman microscopes (which measure light scattering), the research team also digitally recreated sections of the rocks using a supercomputer that processed thousands of images from two high-resolution imaging techniques.
The first technique was computerized tomography, or micro-imaging, which uses X-rays to examine the hematite within the rocks.
The second was a focused ion beam, which scans small slices of rock – 200 nanometers thick – using an integrated electron microscope that takes an image between each slice.
Both methods produced piles of images used to create 3D models of different targets.
The 3D models then allowed the researchers to confirm that the hematite filaments were undulating and twisted, and contained organic carbon, characteristics shared with modern-day iron-eating microbes.
In their analysis, the team concluded that the hematite structures could not have arisen through rock compression and heating (metamorphosis) over billions of years.
They noted that the structures appeared to be better preserved in finer quartz (less affected by metamorphism) than in coarse quartz (which underwent more metamorphism).
The researchers also looked at the levels of rare earth elements in the rocks loaded with the fossils, and found that they had the same levels as other ancient rock samples.
This confirmed that the sea floor sediments were as old as the surrounding volcanic rocks.
Prior to this discovery, the oldest previously reported fossils were found in Western Australia and dated to 3.46 billion years old, although some scientists have also disputed their status as fossils, arguing that they are not biological in origin.
(Daily Mail)