Life On Earth Might Have Started Inside Comet Craters

Large comet craters filled with seawater might have been the ideal habitat for the first life forms. solarseven/Shutterstock

The origin of life is an often debated topic, and there are still many uncertainties as to where and how life started on our planet. Now, a new study might have found an answer.

A team of geochemists from Trinity College Dublin think that large meteorite and comet impacts into the primordial sea provided the right conditions and structures to facilitate the formation of life. These celestial bodies delivered complex chemicals and produced the right geological conditions for life to thrive.

“Previous studies investigating the origin of life have focused on synthesis in hydrothermal environments,” lead author Edel O’Sullivan said in a statement. “Today these are found at mid-ocean ridges – hallmark features of plate tectonics, which likely did not exist on the early Earth. By contrast, the findings of this new study suggest that extensive hydrothermal systems operated in an enclosed impact crater at Sudbury, Ontario, Canada.”

None of the original ancient craters remain, so the Sudbury basin is the next best thing. It is an old crater, formed 1.8 billion years ago by a comet 10 to 15 kilometers (6 to 9 miles) across. The team analyzed a geological layer inside the basin, called Onaping Formation, that measures 1.4 kilometers (0.87 miles) thick.

“Due to later tectonic forces, all the rocks of the once 200 kilometer-wide structure [the impact crater] are now exposed at the surface rather than being buried,” said Professor Balz Kamber, senior author on the study. “This makes it possible to take a traverse from the shocked footwall through the melt sheet and then across the entire basin fill. To a geologist, this is like a time journey from the impact event through its aftermath.”

In the study, published in Geochimica et Cosmochimica Acta, the researchers show that the most recent deposits are richer in carbon and hydrothermal metals, indicating what went on in the aftermath of the impact. The crater was immediately filled with seawater, but it then became isolated from the open ocean. Chemical reactions promoted the formation of hydrothermal activity, and microbial life within the crater created the build-up of carbon we see today.  

The team think Sudbury is analogous to the impact craters that formed during the late heavy bombardment. If this is the case, then the craters may have provided the stable, warm, isolated environment necessary for life to form.  

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