Ultra-clean Archean drilling (AIDP)

Hopanes and steranes had been repeatedly reported from late Archean sediments, implying that oxygenic photosynthesis was in place ca. 300 Myr before rare sulfur isotopes started recording incipient atmospheric oxygenation and that eukaryotes had evolved more than 1 Gyr before the oldest eukaryotic acritarchs appear in the rock record. But signs of contamination started to accumulate. In 2012 we drilled unprecedentedly clean holes into the thermally best preserved Archean rocks that are located on the Pilbara Craton in NW Australia. Only water, spiked with fuorescent dye and synthetic isotopically-labeled hydrocarbon tracers was used as a drilling fluid. The results caused a paradigm shift in our understanding of the early evolution of life on Earth—the absence of biomarkers and indicators of high thermal maturation imply false positives in previous reports. Archean rocks have been reset and carry no biological information in the form of hydrocarbons, thereby reverting the emergence of eukaryotes to dates provided by the microfossil record.

Reappraisal of hydrocarbon biomarkers in Archean rocks (PNAS)

Drilling deep into Earth's history (Max Planck Research)

Drilling the cleanest Archean rocks. Night shifts (above) were partially necessary to compensate for the slow penetration that occurred as a consequence of abstaining from synthetic lubricants. Fresh core samples (below) intended for biomarker analyses were immediately sealed under Argon and frozen.

Drilling with Mountain Dew? We used only clean water, spiked with isotopically labeled hydrocarbons and a fluorescent dye, as a drilling fluid. This helped identifying the penetration depth of potential contaminants into samples.

Archean stromatolites, such as these conical examples from the Trendall locality (left) represent some of the earliest evidence for life on Earth. The AIDP-2012 field team (below): Christian Hallmann, Katherine French, Roger Buick and Les Bonzer.