In 2005, the first mission that planned to collect samples from an asteroid- the Hayabusa spacecraft launched by the Japanese- reached Itokawa, its target asteroid. Five years later Hayabusa has successfully returned to Earth along with a valuable cargo of samples. In the following years, scientists have been heard at work, analyzing the samples in order to understand the history of the asteroid and how it formed. The results were recently published in a per-reviewed journal in many interesting details have been learned.
Itokawa, which is held together by shield gravity, was revealed to be almost 4, 6 billion years old, on par with the age of the solar system. Originally, the asteroid was larger and more impressive but a direct collision with another asteroid 1, 5 billion ago reduced it to the state in which it is today. Itokawa has also orbited with the main asteroid belt until recently when it joined the Near Earth Asteroid orbit, which means that it may collide with Earth one day, unless it breaks apart before it gets too near.
More than 1,000 samples were collected from Itokawa. Some of them contain micro phosphate minerals which were used in tests along uranium to determine the exact age of the satellite at around 4.64 billion dollars with an error space of 180 million years. Further analysis of found isotopes confirms the collision but the exact date is harder to match in this case.
The mission was successful despite a few technical problems. A solar flare hit the spacecraft soon after launch but it continued its mission. A deployable lander disappeared and the spacecraft was forced to land in order to collect the sample. But the problems did not hinder the project and the mission was completed.
The Japanese space agency has sent Hayabusa2 to examine the Ryugu asteroid. It is hoped that it will bring back new samples that will further improve our understanding of asteroids.