Through the Ocean to the Mantle: Twenty Thousand Leagues Under the Seas with a Fleet of Floating Seismic Robots

n the last few decades, seismologists have mapped the Earth's interior (crust, mantle, and core) in ever increasing detail. Natural earthquakes, the sources of energy used to probe the Earth's inside via seismic computerized tomography, occur mostly on tectonic plate boundaries. Seismometers, the receivers of earthquake wave motion, are located mostly on dry land. Such fundamentally inadequate 'source-receiver' coverage leaves large volumes inside the Earth entirely unexplored. Here be dragons! Placing seismic stations on the ocean bottom is among the solutions practiced successfully today. But there are exciting alternatives. Enter MERMAID: a fully autonomous marine instrument that travels deep below the ocean surface, recording global seismic activity - and marine environmental data - and reporting it by surfacing for satellite data transmission. This presentation will discuss a century of Earth imaging, a decade of instrument design and development, and a day in the life of exploring the challenging - and wet - places that our scientific journey has taken us.