Mysterious Asteroid Unmasked By Space Probe Flyby
This photo of the asteroid Lutetia is one of the closest views ever of the asteroid. It was taken from a distance of about 80,000 km during a July 10, 2010 flyby by Europe's comet probe Rosetta. Full Story.
Credit: ESA

A European spacecraft zoomed by past a mysterious asteroid Saturday to take the first-ever close look at the space rock while flying more than 282 million miles from Earth.

The European Space Agency?s (ESA) Rosetta space probe flew past the asteroid Lutetia, an object discovered in 1852 that appeared only as a bright speck in the sky to astronomers until today.

The first new photos of the asteroid revealed Lutetia to be a lumpy rock with a potato-like appearance. Rosetta was about 1,900 miles (3,100 km) from the asteroid at its closest approach.

The enigmatic space rock, which is about 62 miles (100 km) wide, is from the main asteroid belt that orbits between Mars and Jupiter. From Earth, Lutetia simply appears as little more than a single point of light to ground-based telescopes.

As a result, not much was known about Lutetia, including what it looks like. Data from Rosetta?s encounter could provide more conclusive evidence about the asteroid's dimensions and composition. [More asteroid photos.]

?We know approximately its size and rotational period,? Rosetta project scientist Rita Schulz said in a live webcast during the probe?s flyby. ?The rotational period is something like eight hours, and that will be confirmed after the flyby. We are now going to get the details. What is very important for us is the composition of the asteroid."

The asteroid flyby was actually a pit stop for Rosetta, which continued on toward its main target ? comet 67P/Churyumov-Gerasimenko

The spacecraft launched in 2004 and is expected to arrive at the comet in 2014. Rosetta also visited a different space rock, the asteroid Steins, in 2008.

Asteroid blind date

Saturday's asteroid flyby was watched over by dedicated team of mission scientists at the ESA Space Operations Center in Darmstadt, Germany. The rendezvous was webcast live on ESA's website.

At 1514 GMT (11:15 a.m. EDT), Rosetta Spacecraft Operations Manager Andrea Accomazzo confirmed that the probe had entered autonomous tracking mode in preparation for the flyby. The navigation camera was used to keep the spacecraft pointed at Lutetia.

The closest encounter occurred at approximately 1610 GMT (12:10 p.m. EDT), with Rosetta traveling at a relative speed of 32,400 mph (52,142 kph).

ESA scientists were able to track Rosetta up to five minutes to closest approach, after which the radio signal with the probe was lost as the spacecraft turns its antenna away from Earth and faces the asteroid instead.

After approximately 40 minutes, a series of maneuvers restored the antenna?s Earth lock, and the probe began successfully transmitting data and telemetry back to its ground controllers once again. ?

ESA scientists hope the observations from the Lutetia flyby will contribute to the relatively small body of knowledge about asteroids.

Unmasking asteroid Lutetia

The close pass allowed Rosetta about two hours of observation time to scrutinize the asteroid Lutetia.

Rosetta will continue beaming this data to Earth, and the first close-up pictures from the quick visit are expected to be released later tonight. Preliminary images from ESA were released in the lead up to the encounter, showing Lutetia looming larger and larger as Rosetta approached within about 49,700 miles (80,000 km).

The data collected from Rosetta?s visit will provide valuable observations for asteroid science, and will at least give scientists preliminary information that can then be corroborated through ground-based observations. And, the findings will not only apply for Lutetia, but for other asteroids as well.