A team led by geologist Jaesoo Lim of the Korea Institute of Geoscience and Mineral Resources (KIGAM) has discovered stromatolites beneath an asteroid impact crater in South Korea's Jeokjung-Chogye Basin. The crater was created by an impact around 42,000 years ago.
Stromatolites are layered structures built by microbial mats, similar to some of the oldest known evidence of life on Earth.
The discovery suggests that the heat from the impact created a long-lasting hydrothermal environment akin to hot springs, where microbial communities could thrive. Such environments may have been common during the era of heavy bombardment billions of years ago.
The stromatolites, measuring 10 to 20 centimeters in diameter, were found to contain elevated levels of europium, a rare earth element that becomes more soluble in hot hydrothermal fluids. This, along with high calcium, calcite, and sulfur levels, indicates the lake was hydrothermal in nature.
Radiocarbon dating suggests the stromatolites formed between 23,400 and 14,600 years ago, meaning the hydrothermal lake persisted for tens of millennia.
The finding supports the theory that asteroid impacts may have helped make Earth habitable by creating 'oxygen oases'-pockets where microbial metabolism produced oxygen before the Great Oxidation Event 2.4 billion years ago.
Researchers say the discovery also raises hopes for finding similar signatures on Mars, where impact craters may harbor buried stromatolite remains.