First life on earth study: Ontario’s comet impact crater holds incredible clues

Scientists from Trinity College Dublin's School of Natural Sciences have made an interesting discovery that may answer some of the mysteries surrounding first life on earth. The scientists have a strong explanation on the subject. The paper have been published in the journal Geochimica et Cosmochimica Acta. This immense discovery was made possible by an impact crater at Sudbury, Ontario, Canada.

According to the study, early earth’s oceans were bombarded by large meteors, comets and asteroids, which were responsible for planting the seeds of life that then took root after certain hydrothermal systems started operating, presumably giving way to first life on earth. The impact craters generated tremendous amount of heat. Seawater soon filled the craters and remained sub-marine throughout deposition.

Studying the impact crater at Ontario, geochemists found out that the water that accumulated inside the crater remained isolated for a long time. This isolation enabled deposition of more than 1.5km of volcanic sediment and rocks. The lower part of the crater was made up of rocks formed when water entered the crater. The floor of the crater was covered by melting rocks, created by the impact.

Hydrothermal activity started after volcanic rocks were deposited through fuel-coolant reactions. Reduced carbon started appearing above these deposits but within the basin fill. As a result the volcanic products became more basaltic. Presence of carbon in such rocks baffled scientists for a long time. The study explained that it was microbial life inside the crater that was responsible for carbon creation and depletion of vital nutrients such as sulphate.

“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,” First author Edel O'Sullivan, now a PhD candidate in Switzerland, said in a press release.

The crater walls eventually collapsed allowing replenishment of nutrients from surrounding water. Thus, these isolated craters that had their own hydrothermal systems and experienced basaltic volcanism were the stepping stones to life. The interaction between sea water and impact-heated rock enabled synthesis of complex organic molecules. The enclosed crater became a microhabitat within which life flourished.

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