A team of researchers has zeroed in on the date that microbial life populated the hydrothermal system under the 78 million year old Lappajärvi impact structure. The 34Sulfur-depleted pyrite is consistent with microbial sulfate reduction. More evidence of microbial colonization appears about 10 million years post-impact as the temperature continued to gradually decrease. These minerals feature 13 Calcite, which forms in association with microbial sulfate reduction. Their methods of analysis can be used to study the microbial colonization of other impact structures on Earth.