Scientists have discovered living, methane-producing microbes deep inside a massive meteorite impact crater in Sweden, and the find could change the way researchers think about where life can survive — on Earth and beyond.
The study focused on the Siljan crater, one of Europe’s largest known impact structures, formed when a meteorite struck the planet hundreds of millions of years ago.
More than 400 metres below the surface, inside fractured rock created by the ancient impact, researchers found microorganisms that are actively producing methane gas.
This process, known as methanogenesis, is considered one of the oldest forms of metabolism on Earth.
It likely played a role in the earliest stages of life, when the planet’s atmosphere looked very different from today’s.
To study the microbes, the team collected fluids from deep underground and grew the organisms in the lab.
They confirmed that the microbes could create methane using different carbon sources, including traces of natural oil found in the rock.
This is the first time living methane-producing organisms have been confirmed in an impact crater on Earth, showing that these dramatic geological sites can become long-term habitats for life under the right conditions.
Genetic testing revealed that this process is carried out by a partnership between two main types of microbes working together.
While the technical details are complex, the key point is simple: these organisms are uniquely adapted to survive in a dark, deep, high-pressure environment where there is no sunlight. Instead of using light for energy, they rely entirely on chemical reactions with the surrounding rock and fluids.
This discovery has important implications for Mars. Scientists have detected small bursts of methane in the Martian atmosphere over the years, and some of these areas are located near ancient impact craters.
While methane can be produced by non-living geological processes, it is also often linked to biological activity on Earth.
The fact that microbes can thrive in Earth’s impact craters strengthens the idea that similar environments on Mars might once have supported — or could still support — microbial life beneath the surface.
The Siljan crater is now seen as a natural laboratory for studying how life survives in extreme conditions.
It offers a rare glimpse into Earth’s deep biosphere and the incredible resilience of microorganisms.
By learning how life endures in such hidden, harsh environments, scientists are one step closer to answering one of humanity’s biggest questions: are we alone in the universe?
