The history of one of the oldest objects in the Solar system unveiled

An international team of scientists have unveiled details of the history of the asteroid Ryugu, a truly ancient object in the Solar system, after the Hayabusa2 mission brought samples from this asteroid back to Earth. The ESRF was one of the institutes involved in sample characterization, on ID15A. The results are published in Science.

The asteroid Ryugu, located at 200 million kilometres from the Earth, is one of the most primitive objects of the solar system. The Japanese spacecraft Hayabusa2 explored it from 2018 until it came back to Earth two years later with minuscule multiple samples from the asteroid.

Two years later, and thanks to the international collaboration of institutes led by the Japan Aerospace Exploration Agency (JAXA), the first results on the analysis of the samples shed light on the history of Ryugu, from its formation to its collisional destruction.

Researchers used cosmochemical and physical methods at universities and institutes, including the ESRF and four other synchrotron radiation facilities in Japan, United States, and Europe.

The results combined with computer simulation have allowed scientists to picture the origins of Ryugu:  the Ryugu parent body accumulated about 2 million years after the formation of the solar system, and then heated up to about 50°C over the next 3 million years, resulting in chemical reactions between water and rock. The size of the impactor that destroyed the Ryugu parent body, which is about 100 km in diameter, is at most 10 km in diameter, and that the present-day Ryugu is composed of material from a region far from the impact point.

What the data explain

In particular, the seventeen Ryugu samples analysed contain particles (such as Ca- and Al-rich inclusions) that were formed in high-temperature environments (>1000°C). These high-temperature particles are thought to have formed near the Sun and then migrated to the outer solar system, where Ryugu was formed. This indicates that large-scale mixing of materials occurred between the inner and outer solar system at the time of its birth.

Based on the detection of the magnetic field left in the Ryugu samples, it is highly likely that the original asteroid from which the current Ryugu descended (Ryugu’s parent body) was born in the darkness of nebular gas, far from the Sun, where sunlight cannot reach.

The scientists also discovered liquid water trapped in a crystal in a sample. This water was carbonated water containing salts and organic matter, which was once present in the Ryugu parent body. Crystals shaped as coral reefs grew from the liquid water that existed inside Ryugu’s parent body. Rocks that were deeper underground contained more water than those in the surface.

Read more on the ESRF website

Image: A coloured view of the C-type asteroid 162173 Ryugu, seen by the ONC-T camera on board of Hayabusa2.

Credit: JAXA Hayabusa 2

The reign of the dinosaurs ended in spring

The asteroid that killed nearly all dinosaurs struck Earth during springtime.  An international team of scientists from the Vrije Universiteit (VU) Amsterdam (The Netherlands), Uppsala University (Sweden), Vrije Universiteit Brussel (Belgium) and the ESRF, the European Synchrotron (France), have determined when the meteorite crashed onto the Earth, after analysing the remains of fish that died just after the impact. Their results are published in the journal Nature today.

Around 66 million years ago, the Chicxulub meteorite crashed into the Earth, in what today is the Yucatán peninsula in Mexico, marking the demise of dinosaurs and end of the Cretaceous period. This mass extinction still puzzles scientists today, as it was one of the most selective in the history of life: all non-avian dinosaurs, pterosaurs, ammonites, and most marine reptiles disappeared, whilst mammals, birds, crocodiles, and turtles survived.

A team of scientists from the Vrije Universiteit, Uppsala University, and the ESRF have now shed light on the circumstances surrounding the diverse extinction across the different groups. The answers came from the bones of fish that died moments after the meteorite struck.

Read more on the ESRF website

Image: Melanie During points to a section of a Paddlefish dentary showing high bone cell density (i.e. summer)

Credit: Melanie During

Analysing asteroid Ryugu samples

The asteroid Ryugu samples brought back by JAXA’s asteroid explorer “Hayabusa2” in December 2020 are analyzed by six initial analysis teams for one year from June 2021. Among the initial analysis teams, the “Stone Material Analysis Team” and the “Organic Macromolecule Analysis Team” conducts their analysis at the Photon Factory, KEK.

It is thought that asteroids such as Ryugu may have brought water and organic matter to the Earth in the past. By integrating the results of each team’s analysis, we will be closer to solving the great mystery of how life came to be on the Earth.

Read more on the HAYABUSA2-IMSS website

Image : Primordial solar system.