Geochemists from Trinity College Dublin claim to have made a discovery that might just point to where life kickstarted on Earth: at the bottom of comet and meteorite craters.
After taking a trip to Canada’s Sudbury Basin, a team from Trinity got digging. They had an idea and wanted to test it out.
Proposing that impact basins were Earth’s pots and pans, cooking up all the ingredients for life on the planet, they went to the 2bn-year-old impact crater located there to test out their theory.
Earth’s mid-ocean ridges, natural hydrothermal environments, are often the primary focus when investigating the forming of very early life. However, Earth’s shifting plates are a relatively modern phenomenon, so creation of life before this became the norm is a whole different story.
So, prior hydrothermal environments, for example, should be investigated. Where could they be? Probably in the remains of hot, melting craters left by comets and meteorites that crashed into our seas.
If the craters were deep enough, with high enough walls, they could trap sea water inside, mix it with the minerals deposited by space rocks and cook it all up in the hot impact zone.
The massive Sudbury basin was the ideal place to test out the theory, with the team finding evidence of seawater in the basin at a very early stage, isolated from the rest of the sea for long enough to deposit more than 1.5 km of volcanic rock and sediment.
Evidence of layers of deposits showed hydrothermal activity when the water and rocks reacted with the impact melt, with the team’s paper published in Geochimica et Cosmochimica Acta.
Looking at the carbon deposits in the layers above, they established that it was microbial life within the crater basin that was responsible for the build-up of carbon and also for the depletion of vital nutrients.
“There is clear evidence for exhaustion of molybdenum in the water column, and this strongly indicates a closed environment, shut off from the surrounding ocean,” said first author Edel O’Sullivan.
Then, when the crater walls eventually gave way from natural erosion, replenishment of nutrients from the surrounding sea ensued.
These sub-marine, isolated impact basins experienced basaltic volcanism and were essentially equipped with their own, tailored hydrothermal systems.
It’s the second time in a week that Trinity expeditions to the Sudbury basin yielded significant geological findings. Last Thursday, geologists established that our planet’s oldest crystals came from loads and loads of asteroids, again using Sudbury as a test bed.
“There’s a lot we still don’t fully understand about these little guys, but it looks like we may now be able to form a more coherent story of Earth’s early years – one which fits with the idea that our planet suffered far more frequent bombardment from asteroids early on than it has in relatively recent times,” said Gavin Kenny, whose paper appears in Geology.
So that’s early crystals and a boiling, melting pot of nutrients forming life, all discovered by Irish scientists in an Ontario-based wonderland for geologists.
Main comet image via Shutterstock