By any measure, Lutetia is quite large. Planetary scientists believe that it is a primitive asteroid left on the shelf for billions of years because no planet consumed it as the Solar System formed. Indeed, most measurements appear to back this picture, making the asteroid out to be a 'C-type', which contains primitive compounds of carbon.
However, some measurements suggest that Lutetia is an 'M-type', which could mean there are metals in its surface. "If Lutetia is a metallic asteroid then we have found a real winner," says Rita Schulz, ESA Rosetta Project Scientist.
That is because although metallic asteroids do exist, they are thought to be fragments of the metallic core of larger asteroids that have since been shattered into pieces. If Lutetia is made of metal or even contains large amounts of metal, Dr Schulz says that the traditional asteroid classification scheme will need rethinking. "C-class asteroids should not have metals on their surfaces," she says.
Asteroid science stands to gain once this observational conundrum is resolved because Rosetta's data will provide a valuable collection of 'ground truths' that can be used to resolve conflicting ground-based observations not just for Lutetia but for other asteroids as well.
For 36 hours around the moment of closest approach, Rosetta will be in almost continuous contact with the ground. The only breaks will come as Earth rotates and engineers have to switch from one tracking station to another.
Good contact is essential because the uncertainties in the asteroid's position and shape may demand last minute fine-tuning to keep it centred in Rosetta's instruments during the flyby. "The skeleton of the operation is in place, and we have the ability to update our plans at any time," says Andrea Accomazzo, ESA Rosetta Spacecraft Operations Manager.
This is an animation of asteroid (2867) Steins, which was encountered by ESAs Rosetta on September 5, 2008, at a distance of 800 km. The spacecraft is now on its way to Comet 67P/Churyumov-Gerasimenko via asteroid Lutetia.
Steins, the first nominal scientific target of Rosetta, is known to be a relatively rare type of asteroid (E-type) about 5 km across, but its properties were not yet known in detail before Rosettas encounter. Rosetta pre-imaged Steins on 10 March 2006 from a large distance, and obtained a few preliminary data about rotation and shape of the asteroid. The Steins fly-by campaign in 2008 was intended to provide a detailed description of this body and of its near environment from a closer distance.
(Photo Credit: ESA, animation by C.Carreau)
ESA's Rosetta spacecraft flew by asteroid (2867) Steins on September 5, 2008, at 20:58 CEST, ground received time (= spacecraft time CEST + 20 minutes), with a closest approach distance of 800 km.
Steins was Rosettas first nominal scientific target. The spacecraft encountered the asteroid in the course of its first incursion into the main asteroid belt located between the orbits of Mars and Jupiter, while on its way to Comet 67P/Churyumov-Gerasimenko.
The study of asteroids is extremely important because they represent samples of Solar System material at different stages of evolution -- key to understanding the origin of our own planet and of our planetary neighborhood.
(Photo Credit: ESA, image by C.Carreau)
Source: European Space Agency