In a daring manoeuvre, the NEAR Shoemaker spacecraft swooped to within 5 kilometres of the asteroid Eros at 0300 EDT on Thursday morning. This is the closest any craft has come to an asteroid.
"Our proximity to Eros was equivalent to the cruising altitude of a commuter airplane on Earth," says Robert Farquhar, director of the NEAR (Near Earth Asteroid Rendezvous) mission at Johns Hopkins University in Maryland.
Eros is 33 kilometres long, and tumbles end to end as it orbits the Sun. "Getting this close was a little tricky," says Farquar. But Bob Nelson, a member of the NEAR mission team, says:"The whole sequence has gone smoothly so far."
The car-sized NEAR Shoemaker has been orbiting Eros for eight months, sending back data on the asteroid's mass, topography and composition. It took images and collected data for more than five hours during its descent, and it remained at its lowest altitude for 30 minutes.
The images show a surface littered with boulders and craters in "exquisite detail", says Andrew Cheng of the NEAR team. The laser rangefinder and X-ray spectrometer have also obtained their highest resolution to date.
Eros is made from some of the most primitive material in the Solar System. Studies of its composition should help us understand how planets - and perhaps even the Universe - formed and evolved.
Initial data showed that the asteroid's surface is covered with craters and approximately one million house-sized boulders - the result of the battering it has received from other asteroids.
"Eros has a very interesting surface, unlike anything we've ever seen on the Moon or on similar types of asteroid observed from spacecraft," says Clark Chapman from the Southwest Research Institute in San Antonio, Texas.
"A close look at almost any area of Eros's surface will give us detailed information that we don't have now," says Cheng.
An engine burn at 1340 EDT on Thursday will push NEAR Shoemaker back to a stable 200-kilometre orbit. It will stay there for a month before descending to complete its science objectives.
The mission is scheduled to end in February 2001.
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11:17 21 August 2008
