Artist’s impression of Rosetta close encounter with asteroid 21 Lutetia (Image: ESA)
The Rosetta spacecraft is due to make history tomorrow (10 July at 17:10 BST )* when it will fly past the asteroid 21 Lutetia at a distance of 3162 km. 21 Lutetia, which is about 100 km in diameter, will be the largest asteroid so far visited by a spacecraft. Located within the main asteroid belt, at an average distance from the Sun of 364 million kilometres (2.4 AU), Lutetia is a bit of an enigma. Classified as an M-type asteroid, it should therefore be mainly composed of metal. However, Lutetia shows various characteristics which relate it more to primitive C-type asteroids These are asteroids which may resemble carbonaceous chondrite meteorites.
Rosetta was launched in 2004. Its principle objective is to rendezvous in 2014 with the comet 67P/Churyumov-Gerasimenko and then study it in detail over a two year period. The spacecraft consists of a large orbiter, and a small 100 kg lander called Philae. The Planetary and Space Sciences Research Institute (PSSRI) at the Open University has a major involvement with two of the instruments on Philae. Ptolemy is a gas analysis instrument designed to undertake isotopic measurements of samples collected from the comet’s surface. MUPUS will investigate some of the physical properties of the comet’s surface layers. PSSRI members are also co-investigators on a number of other instruments on both the lander and orbiter.
For those of a more romantic disposition, Lutetia is the Latin name for Paris and the asteroid was discovered on November 15th 1852 by Hermann Goldschmidt from the balcony of his Parisian apartment. So, in the tense wait before reaching 67P/Churyumov-Gerasimenko in 2014, members of the Rosetta team will be able to console themselves in the knowledge that: We’ll always have Paris. Sorry about that.
The encounter with Lutetia is one of the major scientific events of the Rosetta mission and the spacecraft will have its full compliment of instruments switched on for the flyby. There will be full coverage on the web.
Live webcast from ESA starting 18:00 CEST (17:00 BST, 16:00 GMT/UTC)
LINK: ESA Rosetta Mission
LINK: Rosetta Blog
Note* (16:10 UTC or GMT))