  We present the current status of geo-neutrino measurements and their
implications for radiogenic heating in the mantle. Earth models predict
different levels of radiogenic heating and, therefore, different geo-neutrino
fluxes from the mantle. Seismic tomography reveals features in the deep mantle
possibly correlated with radiogenic heating and causing spatial variations in
the mantle geo-neutrino flux at the Earth surface. An ocean-based observatory
offers the greatest sensitivity to the mantle flux and potential for resolving
Earth models and mantle features. Refinements to estimates of the geo-neutrino
flux from continental crust reduce uncertainty in measurements of the mantle
flux, especially measurements from land-based observatories. These refinements
enable the resolution of Earth models using the combined measurements from
multiple continental observatories.
