An international research group has found evidence of ancient life in the powerful meteorite crater at Siljan in Dalarna. The findings show that meteorite craters are favorable environments for the colonization of microorganisms on Earth and perhaps on other planets as well.

Much of life on our planet lies hidden beneath our feet.

In an environment called the deep biosphere, which extends several kilometers into the ground, so-called microbial communities thrive. Scientists believe that meteorite strikes may have played a crucial role in the colonization of this harsh habitat.

Crystals on drill tips

In connection with a company recently drilled for natural gas in the Siljansringen area, researchers have been granted permission to investigate drilling tips that have gone down several hundred meters into the bedrock. At the tips have been found small mineral crystals consisting of calcium carbonate and sulfide.

Researchers have analyzed crystals found over 600 meters down the bedrock.

Photo: Henrik Drake

Detailed analyzes of the crystals showed that they contain residual products from ancient microorganisms formed 80-22 million years ago.

- You can say that there are remnants of their digestion you see, says Henrik Drake, a researcher at Linnaeus University who has led the study.

Life on other planets

According to the researchers, the results show that meteorite craters provide optimal environments for the formation of life.

The collision itself breaks up the bedrock, creating space where microbial communities can arise.

The heat from the impact also gives rise to circulation of water, gases and nutrients, which is also a prerequisite for life.

- It has pretty big astrobiological consequences if you think about possible life on other planets, says Henrik Drake.

The theory is that since life has been able to form in impact sites on earth, life may also have been formed in craters on other dead planets, such as Mars.

Formed methane

The researchers have also been able to establish that the microorganisms that lived in the Siljan ring both consumed and formed methane.

- When looking for life on other planets, you are often looking for just methane, as it can be a sign of life, says Henrik Drake.

Being able to carry out deep drilling on Mars is probably quite far ahead.

However, if or when it becomes possible, the methodology used at the Siljansring can be a good alternative to search for ancient activity of microorganisms, the researchers believe.

The results of the study are published in the journal Nature Communications during Friday morning.