The researchers say that their find supports the view that complex life evolved on Earth much earlier than thought:
Earth may have been far more oxygen-rich early in its history than previously thought, setting the stage for the evolution of complex life, according to new research by scientists at the University of Alberta and the University of Tartu in Estonia. The study provides evidence for elevated oxygen levels 2 billion years ago and flies in the face of previously accepted models.
The international team of researchers, led by UAlberta scientists, studied a Russian drill core containing shungite — a unique carbon-rich sedimentary rock deposited 2 billion years ago. The material provides several clues about oxygen concentrations on Earth’s surface at that time, including strikingly high levels of molybdenum, uranium, and rhenium, as well as elevated uranium isotope ratios.
“These trace metals are only thought to be common in Earth’s oceans and sediments when oxygen is abundant,” explained Kaarel Mänd, a PhD candidate in the University of Alberta’s Department of Earth and Atmospheric Sciences and lead author of the study. “These trace metal concentrations are unrivaled in early Earth’s history, suggesting elevated levels of oxygen at the time when the shungite was deposited.”University of Alberta, “Ancient rocks show high oxygen levels on Earth 2 billion years ago” at ScienceDaily
A reader notes this paper Evidence for elevated and variable atmospheric oxygen in the Precambrian offering evidence for high levels of oxygen at 3500 million years ago.
Our physics color commentator Rob Sheldon responds,
This is significant, because the earliest evidence of photosynthesis were these “stromatolite” rocks showing cyanobacterial growth layers. The controversial fossil from Greenland dates to 3700 My, with a more solid fossil at 3400 My.
Now that we see O2 rising in this time period, it supports the Greenland fossil date. So after the Hadean (4000My) and the “late heavy bombardment” 3850My which boiled off the oceans, we get a short 150My in which to refill the oceans, invent not just life but photosynthetic life forms that then create the oxygen atmosphere. And you thought 6My between monkeys and humans was tough!
Perhaps its only in imagination that things can just randomly swish into existence and grow very complex, given enough time. The thing is, there isn’t enough time.