Biosignatures & Paleobiology

Subsurface Microbial Colonization at Mineral-Filled Veins in 2-Billion-Year-Old Mafic Rock from the Bushveld Igneous Complex, South Africa

By Keith Cowing

Status Report

Springer Nature

October 27, 2024

Filed under Bushveld Igneous Complex, geology, Habitable Zone, igneous rock, International Continental Scientific Drilling Program (ICDP), mafic rock, microbiology, microscopy, South Africa, Springer Nature, subsurface microbiology

Subsurface Microbial Colonization at Mineral-Filled Veins in 2-Billion-Year-Old Mafic Rock from the Bushveld Igneous Complex, South Africa — Characterization of a section from the fracture surface to the rock interior. A Photo of the section with a yellow arrow pointing to the fracture surface. B Microscopic image of a region of the section highlighted in a yellow rectangle in A. C Fluorescence microscopy image of the region highlighted by orange rectangle in B. Intensity maps of the section at 1000 cm−1 (D), 1530 cm−1 (E), and 1640 cm−1 (F) obtained by optical photothermal infrared (O-PTIR) spectroscopy. The intensity maps were obtained from the area highlighted with a yellow square in B. G RGB color synthesis of the three intensity maps. A yellow rectangle in G indicates an area where the intensity maps for RGB color synthesis are obtained in Fig. 5A — Springer Nature

Recent advances in subsurface microbiology have demonstrated the habitability of multi-million-year-old igneous rocks, despite the scarce energy supply from rock-water interactions.

Given the minimal evolution coupled with exceedingly slow metabolic rates in subsurface ecosystems, spatiotemporally stable igneous rocks can sustain microbes over geological time scales. This study investigated a 2-billion-year-old mafic rock in the Bushveld Igneous Complex, South Africa, where ultradeep drilling is being executed by the International Continental Scientific Drilling Program (ICDP).

New procedures were successfully developed to simultaneously detect indigenous and contaminant microbial cells in a drill core sample. Precision rock sectioning coupled with infrared, fluorescence, and electron microscopy imaging of the rock section with submicron resolution revealed microbial colonization in veins filled with clay minerals.

The entry and exit of microbial cells in the veins are severely limited by tight packing with clay minerals, the formation of which supplies energy sources for long-term habitability.

Further microbiological characterization of drilled rock cores from the Bushveld Igneous Complex will expand the understanding of microbial evolution in deep igneous rocks over 2 billion years.

Subsurface Microbial Colonization at Mineral-Filled Veins in 2-Billion-Year-Old Mafic Rock from the Bushveld Igneous Complex, South Africa, Springer Nature (open access)

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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