Three rocks hurtling through space appear to be among our solar system's oldest objects.

The ancient asteroids seem to have formed some 4.55 billion years ago, making them older than the oldest meteorites ever found on Earth, said Jessica Sunshine, an astronomer at the University of Maryland who led the team that discovered the objects.

"We have identified asteroids that are not represented in our meteorite collection and which date from the earliest periods of the solar system," Sunshine said. "These asteroids are prime candidates for future space missions that could collect and return samples to Earth providing a more detailed understanding of the Solar System's first few millions of years."

The scientists observed the asteroids with infrared and visible light telescopes on Hawaii's Mauna Kea. They measured the various amounts of different colors of light reflected from the surface and found evidence that the asteroids contain bits of material rich with calcium and aluminum.

An abundance of these elements indicates that the objects were formed when the solar system was young because during that time the first materials to condense into solid particles were rich in calcium and aluminum.

These three asteroids contain two to three times the amount of calcium- and aluminum-rich material of any space rock found on Earth.

The discovery was detailed in the March 20 online edition of the journal Science.

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