Two years ago, the Japanese spacecraft Hayabusa-2 delivered a special cargo to Earth. It contained samples of material collected on the Ryugu asteroid. Analysis of the precious few grams of soil from the asteroid's surface and subsurface has revealed new insights into the past of our planet and that of the entire Solar System.
An international team of scientists led by Dr Marine Paquet and Dr Frédéric Moynier, at the Institut de Physique du Globe de Paris, studied the composition of the sample. They were especially interested in the isotope markings of zinc and copper.
Each chemical element exists in different versions depending on the number of neutrons in its nucleus. This composition does not change the chemical properties, but changes the physical properties because the isotopes have different masses. Some isotopes are so unstable that they decay after a while.
As quoted from IFL Science, isotope ratios are a kind of chemical fingerprint for the materials found. When it comes to asteroid and meteorite samples, this information not only tells us about their current composition but also tells us how these objects formed.
In the case of the Ryugu asteroid, the team confirmed that the isotope signatures of copper and zinc make it similar to the Ivuna meteorite, something that was proposed before the discovery of amino acids in the sample was announced.
The Ivuna meteorite fell in Tanzania on December 16, 1938, and is part of the CI group of carbonaceous chondrites. There are only nine Ivuna meteorites in the world, making them one of the rarest types of meteorites. The Ivuna meteorite is believed to have formed in the outer Solar System and eventually migrated inward.
Ryugu shows compositional similarities to other carbonaceous chondrites, so the researchers wondered if other types might be a better match.
Zinc and copper is where they differ, and for this reason, scientists chose those elements to make tests confirming the association to CI chondrites. Traces of zinc can also be used for other measurements that have had an impact on our planet's history.
The materials from the asteroid Ryugu can be considered pristine in determining the composition of the early Solar System. Meteorites from asteroids that formed closer to the Sun, have a different value than Ryugu. Armed with that, researchers can estimate that an asteroid similar to Ryugu must account for about 6% of Earth's mass.
