A fist-sized rock found in Quebec might challenge the conventional view of when life on Earth began.
In a new study, published Wednesday in the journal Science Advances, researchers examined a rock found near Inukjuak, Que., estimated to be between 3.75 and 4.28 billion years old.
In an earlier paper published in the journal Nature, the researchers from University College London (UCL) suggested that tiny filaments, knobs and tubes found in the rock were created by bacteria around 300 million years before the widely accepted date of the first sign of life on Earth.
At the time, some in the scientific community disagreed that structures found inside the rock were biological in nature, and therefore not a sign of early life.
So UCL researchers re-examined the rock, once a chunk of seafloor, collected by lead author Dr. Dominic Papineau in 2008. After slicing the rock into sections about as thin as paper, they determined that the rock was between 3.75 and 4.28 billion years old due to the rare earth elements in its composition that were at the same levels as other ancient rock specimens of a similar age.
Using various microscopes, as well as a supercomputer to create 3D models of the rock's structures, the researchers confirmed that they were wavy in shape and contained organic carbon, which are characteristics of iron-eating microbes.
The study suggests that the bacteria inside the rock left behind mineralized chemical by-products consistent with the way ancient microbes lived off of iron, sulphur and possibly carbon dioxide.
Researchers also used the imaging to find a centimetre-long stem with parallel branches on one side. The team of researchers said that while some of the structures found in the rock could have been created through chemical reactions, the stem was most likely biological in origin.
"This means life could have begun as little as 300 million years after Earth formed," Papineau said in a press release on Wednesday. "In geological terms, this is quick – about one spin of the sun around the galaxy."
Prior to this finding, the next-oldest biological sample of early life was found in Australia and determined to be about 3.46 billion years old, though some in the scientific community also contest these samples, again arguing that they may not be biological in origin.
This new rock sample could be used to understand how life is formed, and the likelihood that other life is out there.
"These findings have implications for the possibility of extraterrestrial life," Papineau said. "If life is relatively quick to emerge, given the right conditions, this increases the chance that life exists on other planets."
