Asteroid Lutetia Revealed As a Protoplanet

astroengine writes "Asteroids visited by spacecraft have all turned out to be piles of rubble or chunks broken off of larger bodies, but that's not the case with 21 Lutetia, a 75-mile long, 47-mile wide body orbiting in the main belt of asteroids between Mars and Jupiter. Europe's comet-bound Rosetta probe flew by Lutetia last year and gave scientists a big surprise. With its dense body and an interior that seems to have survived intact, the large asteroid appears more like a protoplanet — a leftover building block from the formation of the solar system."