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Particles collected by spacecraft help date ancient asteroid Itokawa

By Brooks Hays
Particles collected by spacecraft help date ancient asteroid Itokawa
Scientists analyzed mineral grains collected from the asteroid Itokawa. Photo by JAXA

Aug. 27 (UPI) -- For the first time, scientists have used particles collected in space to establish the age of an asteroid.

After analyzing particles collected by the Japanese Space Agency's Hayabusa probe, researchers established an absolute origin date for near-Earth asteroid Itokawa.

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Researchers determined Itokawa is as old as the solar system. Phosphate mineral grains suggest the asteroid is 4.6 billion years old. Scientists also determined Itokawa collided with another large asteroid around 1.5 billion years ago.

Scientists measured the ratios of uranium and lead isotopes found in Itokawa particles using the Secondary Ion Mass Spectrometry. Because different uranium and lead isotopes have verified half-lives, scientists can determine when phosphate minerals crystalized.

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The new analysis -- detailed this week in the journal Scientific Reports -- proved Itokawa's particles are very similar to chondrites with low levels of lead and other metals, often called LL chondrites. or LL ordinary chondrites.

LL chondrites are the type of asteroid that most frequently collide with Earth, and the latest findings provide a link between groups of asteroids and historic meteorite collisions.

But while the paths of most LL chondrites were dictated by collisions a few billion years ago, Itokawa experienced shock metamorphism relatively recently. Chelyabinsk meteorite fragments also revealed evidence of a more recent shock.

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"This conclusion enables us to establish constraints on the timescale of asteroid disruption frequency, the validity of the crater chronology and the mean lifetime of small NEAs," researchers wrote in their paper.

To better predict the risk of asteroid impacts, researchers need to better understand how asteroid belt collisions alter the trajectories of large space rocks. The study of asteroid particles can help scientists trace the evolution of large space rocks in the wake of significant collisions.

Early this month, NASA's spacecraft OSIRIS-REx began its approach to the asteroid Bennu. The mission will culminate in the collection of surface particles.

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