Burying biosignatures in the rock record

Signs of microbial life within the rock record – known as ‘biosignatures’ – are notoriously hard to identify. This is especially true when we’re looking at ancient rocks that have experienced high temperatures and pressures as a result of being buried within the Earth’s crust – a process known as metamorphism. Together with Dr. Sami Mikhail in Dr. Anat Shahar‘s lab at the Geophysical Laboratory, Carnegie Institute of Washington, we are experimentally investigating how you go from a microbe in a mineral deposit (in this case bacteria within hot spring carbonate) to a biosignature in a rock that has been squashed and cooked, simulating what happens in nature.

This is achieved using a piston cylinder press:


We are currently squashing our sample at 500 °C (temperature shown inset) and 800 MPa, which is roughly equivalent to being buried 27 km in the Earth’s crust.