On an autumn night in 1852, amateur astronomer Hermann Goldschmidt was observing the skies from the balcony of his Paris apartment when his small telescope revealed a speck of light that no one had ever seen before: an asteroid. It was named Lutetia, for the Roman city that became Paris.
For the next century and a half, Lutetia remained little more than a speck of light in astronomers' telescopes. But last July scientists got to know it a lot better when the Rosetta spacecraft flew by it. The European probe found that Lutetia is dense and heavy, indicating that it's probably a solid chunk of rock and metal, and not a loosely held together "rubble pile" as many other asteroids are.
Lutetia is the largest asteroid yet visited by a spacecraft -- an average diameter of about 75 miles -- so there was a lot for Rosetta to see. Its pictures showed that the surface is covered with a layer of dirt that's more than a third of a mile thick. The dirt has formed over the eons as other space rocks have pounded Lutetia, pulverizing the asteroid's surface.
Collisions by some of the bigger space rocks have left impact craters -- hundreds of them are visible in Rosetta's pictures. As scientists draw maps of Lutetia's surface, they'll name many of the craters and other features in the pictures. And they already have a theme for the names: cities, rivers, and provinces of the Roman Empire and surrounding lands at the time Rome controlled the city of Lutetia.
Script by Damond Benningfield, Copyright 2011