Lutetia Asteroid 21

Astronomical specifications: Discovery  Nov 1852 by Hermann Goldschmidt Orbital characteristics: Aphelion  2.834 AU Perihelion  2.036 AU Semi-major axis  2.435 AU Eccentricity  0.164 Orbital periode rond Sun  1387.902 days Average orbital speed  18.92 km/s Inclination to Sun equator  3.064 deg Physical characteristics: Dimensions  132 x 101 x 76 km Volume  650x 1012 m³ Mass  1.7x 1018 kg Mean Density  3.4 g/cm³ Equatorial surface gravity  ~0.025 m/s² Escape velocity  ~0.06 km/s Rotation period  0.3402 days Surface temperature  ~172 K Axial tilt   deg Atmospheric composition   Radius   km Surface area   km²

Lutetia orbit on Jan 1, 2009

Descriptions & Discovery:

• 21 Lutetia is a large main-belt asteroid of an unusual spectral type. It measures about 100 kilometers in diameter (130 km along its major axis). Lutetia is to date the largest asteroid to have been visited by a spacecraft; the Rosetta probe.
• Lutetia was discovered on November 15, 1852, by Hermann Goldschmidt from the balcony of his apartment in Paris. A preliminary orbit for the asteroid was computed in November-December 1852 by German astronomer Georg Rümker and others. In 1903, it was photographed at opposition by Edward Pickering at Harvard College Observatory. He computed an opposition magnitude of 10.8.
• It is classified an M-class asteroid meaning it is composed primarily of metal. However, little evidence exists of metal on the surface which suggests a more common C-class asteroid. Lutetia is 100 km wide and heavily cratered. It is nearly 4.5 billion years old, just as Earth is, and may be left over from the early creation of the solar system.

Mission details:

• On July 10, 2010 the European Space Agency's spacecraft Rosetta, on its way to a 2014 rendezvous with a comet, flew by the metallic asteroid Lutetia. The probe passed by at a minimum distance of 3160 kilometers, traveling at speeds of 15 km per second. In addition to taking several highly successful images of the rock it attempted to gather some floating dust to analyze as well.
• The Rosetta probe found that the asteroid is covered with a regolith, estimated to be 600 m thick, that has softened the outlines of many of the larger craters.

Lutetia missions: