PARTICLES COLLECTED BY HAYABUSA GIVE ABSOLUTE AGE OF ASTEROID ITOKAWA

Aug 27, 2018

Understanding the origin and time evolution of near-Earth asteroids (NEAs) is an issue of scientific interest and practical importance because they are potentially hazardous to the Earth. However, when and how these NEAs were formed and what they suffered during their lifetime remain enigmas.

Japanese scientists, including those from Osaka University, closely examined particles collected from the asteroid Itokawa by the spacecraft Hayabusa, finding that the parent body of Itokawa was formed about 4.6 billion years ago when the solar system was born and that it was destroyed by a collision with another asteroid about 1.5 billion years ago. Their research results were published in Scientific Reports.

Focusing on a few micrometers of phosphate minerals, which are rarely found in Itokawa particles, the scientists performed precise isotope analyses of uranium (U) and lead (Pb) in Itokawa particles of about 50 ?m in diameter using Secondary Ion Mass Spectrometry (SIMS).

Lead author Kentaro Terada says, “By combining two U decay series, 238U-206Pb (with a half-life of 4.47 billion years) and 235U-207Pb (with a half-life of 700 million years), using four Itokawa particles, we clarified that phosphate minerals crystalized during a thermal metamorphism age (4.64±0.18 billion years ago) of Itokawa’s parent body, experiencing shock metamorphism due to a catastrophic impact event by another body 1.51±0.85 billion years ago.”

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