Asteroid fly-by success!

Asteroid Lutetia

An amazing image of asteroid Lutetia taken at the moment of closest approach during the fly-by successfully accomplished by the Rosetta spacecraft.

  • Fly-by of asteroid of Lutetia accomplished
  • Rosetta spacecraft worked flawlessly
  • Now on target for Comet Churyumov-Gerasimenko

Asteroid Lutetia has been revealed as a battered world of many craters.

The European Space Agency’s (ESA) Rosetta mission has returned the first close-up images of the asteroid, showing that it is most probably a primitive survivor from the violent birth of the Solar System.

Asteroid Lutetia

At a distance of 36,000km, the OSIRIS Narrow Angle Camera (NAC) took this image of Lutetia, catching the planet Saturn in the background.

The fly-by has been a spectacular success with Rosetta performing faultlessly. Closest approach took place at 2:10am Sunday, Sydney time, (16:10 UTC Saturday), at a distance of 3,162 km.

The images show that Lutetia is heavily cratered, having suffered many impacts during its 4.5 billion years of existence. As Rosetta drew close, a giant bowl-shaped depression stretching across much of the asteroid rotated into view.

The images confirm that Lutetia is an elongated body, with its longest side around 130km.

The images come from the OSIRIS instrument, which combines a wide angle and a narrow angle camera. At closest approach, details down to a scale of 60 metres can be seen over the entire surface of Lutetia.

“I think this is a very old object. Tonight we have seen a remnant of the Solar System’s creation,” says Holger Sierks, OSIRIS principal investigator, Max Planck Institute for Solar System Research, Lindau.

Rosetta raced past the asteroid at 15 km/s, completing the fly-by in just one minute. But the cameras and other instruments had been working for hours and in some cases days beforehand, and will continue afterwards. Shortly after closest approach, Rosetta began transmitting data to Earth for processing.

Asteroid Lutetia

A sequence of images taken as Rosetta approached Lutetia. The first image was taken about 9.5 hours before closest approach, 510000 km from the asteroid; the last one about 1.5 hours before closest approach, 8,100 km from the asteroid. The resolution changes from 9.6 km/pixel to 1.5 km/pixel.

Asteroid Lutetia

The final sequence of images of Lutetia before Rosetta's closest approach.

Ready for its next target

Lutetia has been a mystery for many years. Ground-based telescopes have shown that the asteroid presents confusing characteristics.

In some respects it resembles a C-type asteroid, a primitive body left over from the formation of the Solar System. In others, it looks like an M-type asteroid. These have been associated with iron meteorites, are usually reddish in colour and thought to be fragments of the cores of much larger objects.

Rosetta operated a full suite of instruments at the encounter, looking for evidence of a thin atmosphere, magnetic effects, and surface chemical composition as well as the asteroid’s density.

Asteroid Lutetia

Farewell Lutetia — Rosetta looked back for a final glimpse as it zoomed past.

They also attempted to catch any dust grains that may have been floating in space near the asteroid for on-board analysis. The results from these instruments will come in time.

The fly-by marks the attainment of one of Rosetta’s main objectives. The spacecraft will now continue to its primary target, Comet Churyumov-Gerasimenko. It will rendezvous with the comet in 2014, mapping it and studying it. It will then accompany the comet for months, from near the orbit of Jupiter down to its closest approach to the Sun.

In November 2014, Rosetta will deploy a mini-spacecraft called Philae to land on the comet nucleus.

Adapted from information issued by ESA 2010 MPS for OSIRIS Team  / MPS / UPD / LAM / IAA / RSSD / INTA / UPM / DASP / IDA.

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