Meet GOCE, probably the most beautiful robot geologist around. GOCE is a European Space Agency satellite and like a lot of satellites, space probes, and the mars rovers, what they’re doing is best described as geology. GOCE’s function is to look at variations in gravity. It flies in an elliptical orbit around the earth measuring tiny variations in the gravity field of the earth, and these tiny variations are telling us a lot about the planet we live on.
GOCE has just come up with some excellent new data that has mapped the Mohorovicic discontinuity, or Moho for short. The Moho is the boundary between the earth’s thin solid crust on which we live and the mantle that lies beneath.
We always knew roughly where the Moho was. We knew that beneath much of the oceans, the crust is only 10km thick, its thicker beneath the continents and thickest beneath mountain chains. And because these mountain chains are buoyant compared to the mantle, mountain chains actually have to be tens of kilometers thick in order to reach a few kilometers into the sky – a bit like an ice-berg which has 90% of its mass below the water’s surface.
But this new data gives us a whole world view, in superb detail. A triumph for robot geologists everywhere (and their human counterparts who sift through the data, analyse and dedicate their careers to this kind of thing!)
Sadly, in order to pick up these gravitational differences, GOCE flies very low for a satellite and has to use a lot of fuel to keep itself in the right orbit. It is due to run out of fuel in 2014, just five years after launch. But after some great success stories already involving mapping the earth’s gravity field (and here), following ocean currents (see here for an interesting and practical use) and now mapping the Moho, nobody would bet against it coming up with something special before its time runs out.