The jury is still out about how life first formed on Earth, but nailing down when the planet’s continental crust first formed will be key to figuring out the planet’s earliest days.
(CN) — Don’t let their quiet modesty fool you: rocks have a lot to tell. You just need to know where to look and what to ask them.
For example, “Were you around when the Earth formed its crust several billion years ago?”
A team of researchers tested six different deposits of minerals across three continents to answer just that question. A white or colorless mineral, barite, happens to hold a special place with the Earth’s history. The research team’s findings revealed that the Earth’s continental crust formed 500 million years earlier than previously thought, roughly 3.7 billion years ago.
The team will reveal their findings Monday at the European Geosciences Union General Assembly.
To take a step back, the Earth was not always the hospitable place we’ve all come to know. The Earth’s crust first emerged during the Archaean period roughly 4 billion to 2.5 billion years ago. Previous dating methods of the planet’s crust relied on testing marine sedimentary rocks, but those are either scarce or contain altered isotopes that only date back only 3 billion years.
Barite provides a new approach to track down the early days of the Earth’s crust. The rock forms through sulfate releasing from ocean water mixing with barium released by hydrothermal vents. The research team tested the strontium isotopes in the barite at six separate locations. They calculated the isotopes to determine when the weathered continental rock made its way to the ocean and formed into barite.
The barite minerals are record of the Earth’s growth.
“The composition of the piece of barite we pick up in the field now that has been on Earth for three and a half billion years, is exactly the same as it was when it when it actually precipitated,” Desiree Roerdink, geochemist at the University of Bergen in Norway and research lead, said in a statement. “So, in essence, it is really a great recorder to look at processes on the early Earth.”
The results show that weathering on the crust started some 3.7 billion years ago, roughly half a billion years earlier than previously recorded.
“That is a huge time period,” Roerdink said. “It essentially has implications for the way that we think about how life evolved.”
This could in essence throw a wrench into how scientists view life first forming in hydrothermal settings. Life is capricious and there are still conflicting about what came first, whether it was lifeforms on an alien surface or in the ocean.
“We don’t really know if it is possible that life could have developed at the same time on land,” said Roerdink. “but then that land has to be there.”