In a discovery with far-reaching implications, scientists have for the first time pinpointed when microbes began inhabiting a meteorite impact crater – showing that life can not only endure cataclysmic events but also flourish in their wake.
The new study “Deep microbial colonization during impact-generated hydrothermal circulation at the Lappajärvi impact structure, Finland” explores how life returned after a massive meteorite strike. When the meteorite hit Finland about 78 million years ago, it created the 23-kilometer-wide Lappajärvi crater. The impact fractured the ground and generated intense heat, which in turn drove hot water through cracks in the rock. This hydrothermal activity could create a temporary but rich environment for microbes. The big question scientists wanted to answer was: how soon after the impact did life actually return?
To find out, the team studied minerals that filled fractures in the crater rock. These minerals carry tiny chemical fingerprints left behind by microbial activity. In particular, sulfur isotopes in pyrite crystals showed clear evidence of microbes carrying out sulfate reduction, a type of metabolism that occurs without oxygen. By dating the minerals, the researchers discovered that conditions suitable for life – about 47°C – developed 4 to 5 million years after the impact. This means microbes moved in surprisingly quickly once the crater cooled enough to be habitable.
The story didn’t end there. Other minerals that formed more than 10 million years later showed signs of methane production and consumption, meaning different microbial groups were active long after the initial colonization. The crater’s fractured rocks, hot fluids, and chemical gradients created both shelter and energy sources, allowing microbes to survive and evolve for tens of millions of years.
The findings show that impact craters are not just short-lived habitats but can serve as long-term microbial homes deep underground. This gives us the first solid timeline linking a meteorite impact, the creation of a hydrothermal system, and microbial colonization. Beyond Earth, the study also has big implications: similar craters on Mars or icy moons may once have provided, or could still provide, the right conditions for life.
The news was released by Linnaeus University.