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Artist's illustration of the Hayabusa spacecraft to the asteroid Itokawa in 2005. Image via JAXA.
In 2005, the first asteroid sample return mission – the Japanese spacecraft Hayabusa – reached its target, the asteroid Itokawa. In 2010, Hayabusa (Japanese for "Peregrine Falcon") returned to Earth with its precious cargo of dust samples from the asteroid. In the years that followed, scientists studied these samples to better understand the origin and the geological history of Itokawa. Now a new peer-reviewed study published in the journal Scientific reports August 7, 2018, details for the first time new discoveries regarding the age and origin of Itokawa.
The asteroid – essentially a "pile of rubble" maintained by gravity – is 4.6 billion years old, at about the same age as the solar system itself. But this is not always the case now; Scientists determined that the "original" Itokawa collided with another asteroid about 1.5 billion years ago and that it was almost destroyed. The resulting debris, however, has been reassembled in the "pile of rubble" we see today. In addition, it seems that Itokawa inhabited the main asteroid belt until only a few hundred thousand years ago. It is now in the form of an asteroid close to the Earth (NEA) or an asteroid that crosses the Earth. may According to scientists, it would result in a collision with the Earth in the next one million years or so. This possibility is based on a previous study that simulated 39 almost identical orbits of the asteroid. It is also possible that Itokawa separates during this period.
Close view of one of the microscopic dust particles of the asteroid Itokawa, with various composition elements noted. Image via the University of Osaka.
Another grain of Itokawa dust, showing incredible detail under a scanning electron microscope. Image via ESA.
This view of a speck of dust shows the complex structure in every detail. Image via JAXA.
As stated in the study:
The results indicate that an impact of the Earth on [Itokawa] is likely here a million years.
Hayabusa collected more than 1,000 tiny grains of dust from Itokawa. Some of these grains are microscopic phosphate minerals. The researchers measured the amount of uranium present in the phosphate grains as lead. Uranium disintegrates at a known rate, which helped determine the specific age of the asteroid – 4.64 billion years, or 180 million years. The researchers were also able to analyze different isotopes of uranium and lead in the samples, which proves that Itokawa collided with another asteroid about 1.51 billion years ago. There is however more room for maneuver at this age – the collision could have been as recent as 660 million years ago, or 2.36 billion years ago.
Itokawa, seen by the Japanese spacecraft Hayabusa in 2005. The asteroid is essentially a "pile of debris" material maintained by gravity. Image via JAXA / ISAS.
Mineralogy and geochemistry of dust particles have also been found to be similar to chondrite meteorites, which regularly fall on Earth. The researchers however determined that the chronology of evolution was different from that of the origin of chondrite meteorites.
Hayabusa's mission was incredibly successful in bringing the first samples of an asteroid back to Earth, but it also had problems. The spacecraft was hit by a solar flare shortly after its launch, but it was still able to continue its journey, reaching Itokawa in 2005. A small lander included in the mission was lost after the deployment and never reached the 'asteroid. The main spacecraft itself, however, was able to land briefly to collect the necessary dust samples. These samples were finally returned to Earth on June 13, 2010, landing inside their armored capsule.
The Japanese space agency JAXA has followed Hayabusa's success with Hayabusa2, who is currently examining the Ryugu asteroid – about half a mile across a rough diamond. As the first mission, Hayabusa2 will return samples to Earth for further study by scientists. Hayabusa2 arrived in Ryugu on June 27, 2018 and, as noted earlier in EarthSky, the mission team has just chosen a landing site for its lander, called the MASCOT (Mobile Asteroid Surface Scout). Hayabusa2 will leave Ryugu in December 2019, bringing his samples back to Earth for further analysis and study in December 2020.
The return capsule that transported the Itokawa dust grains samples to Earth on June 30, 2010. Image via JAXA.
Origins, Spectral Interpretation, Resource Identification, Security, NASA's Regolith Explorer (OSIRIS-REx) is also on final approach to the asteroid Bennu, due to arrive in December. OSIRIS-REx will also take samples, which will return to Earth in September 2023. OSIRIS-REx has just released its first distant images of Bennu on August 17, 2018.
Itokawa was discovered in 1998 by the LINEAR project at Lincoln's experimental testing site in Socorro, New Mexico. It is rather small – only 630 (± 60) meters long and 250 (± 30) meters wide. It was named after Hideo Itokawa (1912-1999), a Japanese scientist specializing in rockets.
Conclusion: Itokawa was the first asteroid from which samples were obtained and returned to Earth. The continuous study of these samples revealed for the first time the exact age and geological history of the asteroid, while providing more valuable insights into asteroid formation in general.
Source: Thermal Stories and Impact of 25143 Itokawa Recorded in Hayabusa Particles
Via scientific reports.
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