罗塞塔探测器经过小行星卢滕西亚
2010-07-11 09:00阅读：
罗塞塔探测器经过小行星卢滕西亚
The encounter took Rosetta to 3,162km from Lutetia at
closest approach. The probe flew past at 15km/s
Europe's Rosetta space probe has flown past the Asteroid Lutetia,
returning a stream of scientific data for analysis.
The huge rock - about 120km in its longest dimension - is the
biggest asteroid yet visited by a satellite.
Pictures showed Lutetia to be quite irregular in shape, its surface
marked by a number of wide impact craters and even some intriguing
grooves.
Rosetta's encounter with the asteroid occurred some 454 million km
from Earth,
beyond the orbit of Mars.
Seen high above Lutetia is the planet Saturn and its
rings
Scientists hope the data will help them
determine Lutetia's true nature.
'The pictures are majestic; they take my breath away,' Professor
David Southwood, the European Space Agency's director of science,
told BBC News.
'It is an historic day, Europe once again proving it can do major
steps in Solar System exploration. Everything worked like
clockwork. It really was picture perfect,' he said.
Earth-based telescopes have had great difficulty in classifying
Lutetia.
Some observations have suggested it is a very primitive body,
little changed since its formation (a so-called C-type
asteroid).
Other measurements, though, have also spied what appear to be
metals in its surface, indicating the rock might have undergone a
greater degree of evolution (M-type asteroid).
Lutetia might even be the fragmented remains of a much larger
asteroid smashed apart in a great collision.
Rosetta will attempt to resolve these issues once and for
all.
Nearly all of the Rosetta mission's instruments were switched on
for a period of several hours around closest approach (1544 GMT;
1644 BST; 1744 CEST).
Multi-wavelength cameras and spectrometers, magnetic field and
plasma experiments, dust instruments, a radio science experiment -
all were tasked with gathering as much information as possible as
the spacecraft whizzed by at the relative speed of 15km/s and a
minimum distance of 3,162km.
Scientists say it will be some days before they can start to make
some definitive statements about Lutetia's origins.
THE ROSETTA PROBE MAKES ITS CLOSE PASS OF ASTEROID
LUTETIA
Asteroids are the ancient remnants left over from the formation
of the Solar System
Most are made of rock, but some are also composed of metal, mostly
nickel and iron
Their sizes range from small boulders to objects that are hundreds
of km in diameter
Most asteroids reside in the vast region of space that exists
between Mars and Jupiter
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Before this flyby, the largest asteroid encountered by a spacecraft
was Mathilde, which is a little over 50km wide.
Mathilde was visited by the US space agency's (Nasa) Near-Shoemaker
probe in 1997.
Rosetta itself has already made one close asteroid flyby, of the
Steins rock in 2008.
With this latest pass complete, Rosetta is now heading out to its
meeting with the Comet Churyumov-Gerasimenko, set for the May of
2014.
The probe will go into orbit around the 4km-wide ball of ice and
dust and even place a small lander called Philae on its
surface.
Asteroids are the object of keen interest currently. The Japanese
Hayabusa mission has recently returned from the Itokawa space rock,
and next year the US Dawn mission will go into orbit around
Asteroid Vesta.
The American President Barack Obama says Nasa should also have the
goal of trying to send astronauts to an asteroid sometime in the
2020s.
The detail at closest approach is about 60m per pixel. These images
show grooves on the surface
Jonathan.Amos-INTERNET@bbc.co.uk
