Asteroid Ryugu has unexpected 'family ties' near Jupiter

A new study sheds light on the birthplace of asteroid Ryugu, which is now believed to have formed near Jupiter. Previous studies suggested that the asteroid originated beyond the orbit of Saturn.

The return of samples from Ryugu to Earth by the space probe Hayabusa 2 in 2020 set the stage for a new wave of research.

Since then, the samples have journeyed through research facilities around the globe. The tiny, jet-black grains have undergone a variety of tests such as weight measurement, chemical analysis, and exposure to infrared, X-ray, and synchrotron radiation.

Tracing the origins of Ryugu

At the Max Planck Institute for Solar System Research (MPS), one method of analysis proved to be particularly useful. The experts tested the ratios of certain metal isotopes present in the samples.

Isotopes function as distinct signatures of elements, with variants differing only in the number of neutrons contained in their nucleus.

This meticulous study of isotopes has been instrumental in tracing the origins of Ryugu back in the Solar System.

Ryugu’s journey through the solar system

Ryugu, an intriguing near-Earth asteroid, is not originally from the inner Solar System but is believed to have traveled there from the asteroid belt between Mars and Jupiter.

Some scientists suggest its birthplace might even be farther away, beyond Jupiter’s orbit.

To decipher Ryugu’s ancient family ties, researchers compared its characteristics with meteorites – the terrestrial breadcrumb trail left by asteroids.

Unique composition of Ryugu

Detailed studies of Ryugu’s composition have unveiled quite a surprise. While Ryugu matches the carbon-rich structure of the expected carbonaceous chondrites, it belongs to a rare group known as CI chondrites or Ivuna-type chondrites.

Only nine of these exotic specimens have been discovered to date, and they are thought to contain particularly pristine material formed at the outermost edge of the Solar System.

Rethinking the origins of Ryugu

Previously, scientists believed that the specific isotopic composition of CI chondrites suggested their birthplace was beyond Saturn’s orbit, but the new analyses challenge this assumption.

The researchers’ recalculation suggests that a missing fourth component – tiny iron-nickel grains – must have played a part in Ryugu’s formation, leading to a drastic re-evaluation of its origins.

The birth of CI chondrites

The proposed theory suggests that a process of gas evaporation, influenced by the Sun, led to an accumulation of dust and iron-nickel grains outside of Jupiter’s orbit, giving birth to the CI chondrites.

This would place their formation around two million years after that of the Solar System. The new results have shocked even the researchers themselves.

“The results surprised us very much. We had to completely rethink – not only with regard to Ryugu, but also with regard to the entire group of CI chondrites,” said study co-author Dr. Christoph Burkhard.

Formation history of the Solar System

The findings reframe the CI chondrites not as distant relatives of the other carbonaceous chondrites, but rather as younger siblings that formed through a different process and later in time.

The ongoing exploration of Ryugu and its samples will continue to provide new insights into the formation of our Solar System.

“The current study shows how crucial laboratory investigations can be in deciphering the formation history of our Solar System,” said Dr. Thorsten Kleine, Director of the Department of Planetary Sciences at MPS.

Future missions to sample asteroids

As the analysis of Ryugu’s samples continues to unfold, researchers are eagerly anticipating what further secrets the asteroid may hold.

Beyond understanding Ryugu’s birthplace, the findings could have broader implications for future space missions.

With more space agencies turning their attention to asteroid mining and planetary defense, Ryugu’s composition and journey through the Solar System offer a valuable case study.

Future missions could target similar asteroids, seeking to unlock more about the building blocks of planets and the potential for harnessing these celestial bodies for resources.

Moreover, Ryugu’s successful sample return mission sets a precedent for future exploratory missions that will collect, study, and perhaps even manipulate celestial material.

The study is published in the journal Science Advances.

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