Japanese scientists determine age of asteroid Itokawa

Analysis indicates it came from large ancient parent body later destroyed in an impact.
By Laurel Kornfeld | Aug 29, 2018
Japanese scientists who analyzed samples taken from asteroid Itokawa and returned to Earth in 2010 by the Hayabusa probe determined the asteroid came from a parent body that formed 4.6 billion years ago, at the dawn of the solar system.

That body was destroyed in an impact with another asteroid approximately 1.5 billion years ago. Remnants from that impact stuck together over time, producing Itokawa.

Between 100,000 and 400,000 years ago, Itokawa was ejected from the asteroid belt between Mars and Jupiter and propelled into its current near-Earth orbit, where asteroids usually do not survive very long.

Scientists estimate Itokawa will either break apart or hit the Earth within the next million years.

Hayabusa was launched by the Japan Aerospace and Exploration Agency (JAXA) in 2003 with the goal of studying the near-Earth asteroid and returning a sample of it to Earth for analysis.

While Itokawa itself poses no current threat to Earth, near-Earth asteroids could potentially pose hazards to our planet. Understanding their formation and evolution processes is important for scientists in terms of both predicting and addressing potential impacts.

The Japanese scientists, including some from Osaka University, looked at tiny, phosphate-rich minerals found in the particles taken from Itokawa's surface. They then measured the level of uranium inside the particles and determine how much of it had broken down into lead, a process that always occurs at the same pace. This allowed them to put together the asteroid's history.

From this analysis, the scientists learned that the asteroid's phosphate minerals crystallized during a time when the parent body experienced shock from an impacting object.

Another discovery the researchers made is that Itokawa's mineralogy and geochemistry match those of low-iron, low-metal chondrite meteorites that often land on Earth. Chondrites are rocky, non-metallic meteorites that were never modified by melting of their parent bodies.

A paper detailing the scientists' findings has been published in the journal Scientific Reports.



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