Japanese asteroid visitor’s tiny payload delivers big results

In the two years since Japan’s Hayabusa2 jettisoned a small capsule to eagerly waiting scientists in the desert of South Australia, researchers have been picking through its contents, keen to unearth the secrets of our early solar system.

The capsule contained just 5.4 g of material from the asteroid Ryugu, which Hayabusa2, scooped up in a landmark mission in late 2018.

By performing isotopic analysis, French scientists have obtained further insight into the chemistry and origins of the asteroid and furthered our understanding of the early Solar System.

Asteroids are often compared to rubble leftover from a building site, as many represent some of the most primitive and pristine material from the earliest days of the Solar System’s formation. Meteorites from asteroids, although highly prized by researchers, are inevitably contaminated by their passage through Earth’s atmosphere and exposure to weather and other terrestrial processes.

Hayabusa2 (artist's impression)
Hayabusa2 (artist’s impression). Credit: JAXA

Since the samples from Hayabusa2 are directly from the asteroid, they are a game-changer for research into the earliest origins of our solar system. So far, analysis has already shown that Ryugu is close in composition to ‘Ivuna-like’ carbonaceous chondrites (‘Ivuna’ is the type-specimen for this type of meteorite).

This type of chemistry is typical of primitive host asteroids and is similar to the composition of the Sun. Ryugu has also shown a few puzzling isotopic signatures which overlap with other classifications of carbonaceous chondrites.

Read more: First results from Hayabusa’s Ryugu asteroid sample

New analysis has more deeply investigated the isotopic ratios of zinc and copper within the samples. These elements are key to understanding how volatiles are gathered and incorporated into the structure of terrestrial, or rocky, planets.

Asteroid ryugu
Asteroid Ryugu was visited by JAXA spacecraft Hayabusa2 in late 2018. Credit: ISAS/JAXA

This research, recently published in the journal Nature confirms that Ryugu clearly delineates Ryugu from other types of carbonaceous chondrites, confirming that it is actually Ivuna-like. Importantly, the measurement of copper and zinc isotopes has also provided the best estimates for the amounts of these elements in the ‘solar composition’ (the chemistry of the Sun and early Solar System).

Measurements of the isotopic composition of zinc, in particular, are useful for understanding the process of forming habitable planets such as Earth. The research also indicates that Earth contains about 5% of Ryugu-like mass, providing key insights into the formation of Earth.

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