An international team of researchers, including Western's Gordon Osinski, discovered and successfully dated - for the first time ever - the birth of microorganisms in a meteorite crater, confirming that life established itself millions of years after the space rock's initial impact with Earth.
The discovery, which supports the theory that meteorite impacts can create habitable environments on Earth and other planetary bodies, was made in the 78-million-year-old Lappajärvi impact crater in Finland.
The findings were published in the high impact journal, Nature Communications.
Gordon Osinski
"This is incredibly exciting research as it truly connects the dots for establishing life on Earth for the first time," said Osinski, an Earth sciences professor and study co-author. "Previously, we've found evidence that microbes colonized impact craters, but there have always been questions about when this occurred and if it was due to the impact of the meteorite, or some other process millions of years later. Now we have evidence that this impact event created a warm, wet habitable environment right after it formed, which was soon colonized by microorganisms."
Osinski travelled to Finland to work with his international collaborators, assisting in sampling and geological interpretation of the drill core taken from Lappajärvi impact crater.
"This is the first time we can directly link microbial activity to a meteorite impact using geochronological methods. It shows that such craters can serve as lifelong habitats in the aftermath of the impact," said Henrik Drake, a professor at Linnaeus University in Sweden and senior author of the study.
Illustration of new research findings in the Lappajärvi crater, Finland, where traces of ancient life have been discovered in the crater's fractures. The magnified section highlights the blue-marked fracture zones where microbial signatures have been identified. (Henrik Drake, Gordon Osinski)
By combining an array of isotopic analyses of mineral fillings in rock fractures and cavities, the researchers showed microbial colonization (when microorganisms like bacteria and fungi establish themselves and begin to grow) started a few million years after the impact in the crater's hydrothermal system, at temperatures around 47°C. A hydrothermal system is the process where heated water circulates through underground fractures and rock to form chemically modified, superheated fluids.
The chemical signatures the team found in the minerals also indicated microbial sulfate reduction - a common microbial process in the subsurface of the crater. Sulfur is one of the essential elements for life and confirmation of its reduction here provides evidence the microbes lived.
Meteorite sample from drill core collected from Lappajärvi impact crater. (Henrik Drake)
The study also described later mineral formations, formed more than 10 million years after the impact, which show evidence of both methane consumption and production - providing further proof of long-lasting microbial activity.
"What is most exciting is that we do not only see signs of life, but we can pinpoint exactly when it happened. This gives us a timeline for how life finds a way after a catastrophic event," said Jacob Gustafsson, PhD student at Linnaeus University and first author of the study.
