Scientists Discover The True Age Of Asteroid Itokawa, The First-Ever Space Rock To Yield A Dust Sample

Collected by Japan's Hayabusa spacecraft in 2005, the dust samples from asteroid Itokawa have helped scientists piece together the history of this near-Earth asteroid.

Asteroid Itokawa
JAXA / ESO

Collected by Japan's Hayabusa spacecraft in 2005, the dust samples from asteroid Itokawa have helped scientists piece together the history of this near-Earth asteroid.

For the last eight years, researchers all over the world have been studying the precious dust samples brought back by Japan’s historic Hayabusa mission in 2010.

Launched in 2003 by the Japan Space Exploration Agency (JAXA), Hayabusa was the world’s first mission to retrieve samples from the surface of an asteroid. The target of this mission, a small near-Earth asteroid discovered in 1998 and dubbed 25143 Itokawa, has since been the focus of many scientific studies.

And, according to a new paper published last month in the journal Scientific Reports, researchers believe they have finally unlocked its secrets.

This study is the first one to unravel the origin of asteroid Itokawa and present the timeline of its geologic history, reports EarthSky.

By analyzing the chemical composition of several dust grains collected from the asteroid, the team — led by Kentaro Terada of Osaka University in Japan — uncovered the true age of Itokawa and pieced together the history of this intriguing and oddly-shaped space rock.

“Understanding the origin and evolution of near-Earth asteroids (NEAs) is an issue of scientific interest and practical importance because NEAs are potentially hazardous to the Earth. However, when and how NEAs formed and their evolutionary history remain enigmas,” the authors wrote in their paper.

As the Inquisitr previously reported, Hayabusa returned to Earth carrying around 1,500 dust grains from asteroid Itokawa, which the spacecraft managed to snag back in 2005, despite a series of problems that almost made the mission unsuccessful.

After a failed attempt to deploy a lander on the 1,640-foot (500 meters) wide asteroid, the spacecraft was unable to carry out the initial plan of shooting a probe into the surface of Itokawa and grabbing large rock samples, notes Space. However, Hayabusa did retrieve dust samples, one of which was investigated by Terada’s team.

As the researchers pointed out in their study, the sample they looked at “is so fragile that it may not have been collected if the Hayabusa spacecraft sampling mechanism had operated as planned and its impactors struck the Itokawa surface.”

After closely examining the dust grains, the scientists found out that Itokawa was formed during the early days of the solar system and is about 4.64-billion-years-old, give or take 180 million years, Osaka University announced in a news release.

The revelation came after the team studied the tiny particles of phosphate minerals contained within the sample. These enabled them to trace the history of the asteroid back to its beginnings, based on how much of their uranium content had decayed into lead.

This particular reaction occurs at a certain pace and was used to calculate both the age of the asteroid and its geologic evolution.

The findings revealed that Itokawa originated in a much larger parent body, which was subjected to a catastrophic collision with another asteroid some 1.51 billion years ago.

The violent encounter nearly destroyed the parent body, which “was catastrophically disaggregated by one or multiple impacts into numerous small pieces,” Terada’s team wrote in their paper.

Some of these bits and pieces of rock eventually came together to shape Itokawa, now a “greatly diminished, rubble-pile asteroid” held together by gravity, explained the researchers.

The resulting space rock is a silicaceous, or S-type, asteroid, the Inquisitr previously reported, and looks surprisingly like a peanut.

Asteroid Itokawa
A schematic view of the strange peanut-shaped asteroid Itokawa, which displays different densities on different segments of its body. ESO, JAXA / Wikimedia Commons/Resized (CC BY 4.0)

And, while Itokawa is currently found 42 million kilometers (26 million miles) away from Earth, as reported by the European Space Agency, this is not where the asteroid started out.

The scientists discovered that Itokawa was actually born in the asteroid belt that lies between the orbits of Mars and Jupiter. As it turned out, the space rock migrated to its current location sometime between 100,000 and 400,000 years ago.

The story of Itokawa is unlikely to end here. Researchers speculate that, within the next million years or so, the space rock will either break apart or possibly enter a collision course with Earth. This second hypothesis has been amply detailed in a 2005 study published in the journal Icarus and which simulated 39 nearly identical orbits of the asteroid.