Satellite traces Earth’s crust-mantle boundary

BBC : Launched in 2009, the European Space Agency’s Gravity Field and Steady-State Ocean Circulation Explorer ( GOCE), the lowest Earth-orbiting research satellite, has provided new insight into Earth’s so-called Moho boundary. Named for Croatian geophysicist Andrija MohoroviÄiÄ, the Moho marks the border between Earth’s crust and mantle, some 10–70 km below Earth’s surface. The crust, composed mainly of basalt and granite, has a lower density, whereas the mantle, composed mainly of peridotite, has a higher density. The difference in rock density means a difference in mass and, hence, gravity. Because GOCE can detect subtle variations in Earth’s gravitational field, the satellite can be used to determine Moho’s depth, which has been found to be greatest under the big mountains and shallowest under the oceans. Such data could further the study of plate tectonics and the search for new oil and gas reserves.