Deep microbial colonization during impact-generated hydrothermal circulation at the Lappajärvi impact structure,...

Area of Science:

• Astrobiology
• Geochemistry
• Geochronology

Background:

• Meteorite impact structures are potential habitats for microbial life.
• Evidence linking microbial colonization to impact-generated hydrothermal systems is scarce.
• Direct geochronological data for such events are lacking.

Purpose of the Study:

• To provide timing constraints for microbial colonization in the Lappajärvi impact structure.
• To link microbial activity to impact-generated hydrothermal systems.
• To understand the duration of habitability post-impact.

Main Methods:

• Coupled microscale stable isotope biosignature detection.
• Radioisotopic dating of vug- and fracture-filling assemblages in impactites.
• Analysis of mineral precipitation temperatures and isotopic compositions (sulfur, carbon).

Main Results:

• Microbial activity detected at habitable temperatures (47.0 ± 7.1°C) starting around 73.6 ± 2.2 Ma.
• Early pyrite precipitation indicated microbial sulfate reduction (34S-depleted).
• Later mineral precipitation over 10 Myr later showed evidence of anaerobic methane cycling.

Conclusions:

• Meteorite impacts generate long-lived hydrothermal systems conducive to microbial life.
• Microbial colonization can persist as impact craters cool.
• These findings have implications for the origin and evolution of life on Earth and other planets.