Scientists uncover active methane production deep inside Sweden’s Siljan impact crater, offering insights into Earth’s earliest life and the search for life beyond our planet.
Researchers have discovered living microbes producing methane in the fractured rocks of the Siljan impact crater in central Sweden. This breakthrough not only sheds light on one of Earth’s most ancient metabolic processes—methanogenesis—but also strengthens the link between meteorite impact structures and microbial survival in extreme environments.
Methanogenesis is considered one of the earliest metabolisms on Earth, and its presence in deep subsurface environments has long intrigued scientists. Now, for the first time, active microbial methane production has been confirmed in a terrestrial impact crater. Using cultures enriched from fluids 400 meters below the surface, the team demonstrated methane generation from several carbon sources, including indigenous oil.
Genomic and transcriptomic analyses revealed a microbial partnership dominated by Acetobacterium sp. KB-1 and Candidatus Methanogranum gryphiswaldense, operating exclusively via the methyl-reduction pathway. This process left a striking isotopic signature, with δ¹³C enrichment of up to 98.6‰.
“Impact craters are not just geological scars—they can be microbial havens,” says lead author Femke van Dam, Linnaeus University, Sweden. “Our findings suggest that similar environments on Mars could host life, especially given the methane detected in the Martian atmosphere in spatial relation to impact craters.”
Senior author Henrik Drake, Professor at Linnaeus University, adds: “The Siljan crater offers a window into life’s resilience. If microbes can thrive here, they might also persist in impact structures on other planets.”
This discovery provides a new perspective on deep biosphere ecosystems and their role in planetary habitability—on Earth and beyond.
More information
Link to the full article “Active methylotrophic methanogenesis by a microbial consortium enriched from a terrestrial meteorite impact crater” in mBio.
Images from sampling and lab work can be found here. Photo credd: Linnaeus University.