Scientists have proposed a cause for the microscopic etchings seen in volcanic glass from the Earth’s oceanic crust that calls into question the assumption that such etchings are biosignatures.

The “biogenic-looking” corrosion microtextures observed globally in volcanic glass of in situ oceanic crust, ophiolites, and greenstone belts dating back to around 3.5 billion years ago have widely been presumed to be caused by microbes. Authors Jason E. French and David F. Blake analyzed submarine glass taken from the North Atlantic Ocean and suggest an abiotic mechanism involving possible radiation damage and pressure solution etch-tunneling.

The paper, “Discovery of Naturally Etched Fission Tracks and Alpha-Recoil Tracks in Submarine Glasses: Reevaluation of a Putative Biosignature for Earth and Mars,” is published in The International Journal of Geophysics. The findings have important implications for geomicrobiology, astrobiological exploration of Mars, and understanding of the long-term breakdown of nuclear waste glass.