Image provided by Duncan Keenan-Jones, Mayandi Sivaguru, Glenn Fried, and Bruce Fouke, Bruce Fouke Lab
Research funded by the Total Oil Company
This second image of travertine from the Anio Novus aqueduct shows the naturally-occurring fluorescence of different layers of the rock. The fluorescence could be produced by the remains of microbes living within the layers of sediment, the minerals of the rock itself, or both.