Asteroid's zinc, copper shed light on Earth's origins - study

The study is the latest research to come from the analysis of the samples of the Ryugu asteroid brought back to Earth in 2020 by the Japanese mission Hayabusa2.

 Samples of asteroid Ryugu analysed at IPGP.  (photo credit: Institut de physique du globe de Paris)
Samples of asteroid Ryugu analysed at IPGP.
(photo credit: Institut de physique du globe de Paris)

New research on the zinc and carbon isotopes has better clarified the composition of the large asteroid 162173 Ryugu, which may shed light on the origin of life on Earth, a new study has found.

The findings of this French-led study were published in the peer-reviewed academic journal Nature Astronomy.

The study is the latest research to come from the analysis of the samples of the Ryugu asteroid brought back to Earth in 2020 by the Japanese mission Hayabusa2.

Ryugu asteroid and its secrets about the history of the solar system

Ryugu is a large asteroid that sits between Mars and Earth. It has been deemed a potentially hazardous object due to its close orbit and its immense size, clocking in at nearly a kilometer in diameter.

C-type asteroid 162173 Ryugu, seen by the ONC-T camera on board the Hayabusa2 spacecraft (credit: ISAS/JAXA/CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)/VIA WIKIMEDIA COMMONS)C-type asteroid 162173 Ryugu, seen by the ONC-T camera on board the Hayabusa2 spacecraft (credit: ISAS/JAXA/CC BY 4.0 (https://creativecommons.org/licenses/by/4.0)/VIA WIKIMEDIA COMMONS)

But this asteroid also holds numerous secrets about the earliest days of the solar system.

Ryugu is believeved to be an Ivuna-like carbonaceous chondrite (CI chondrite) asteroid, meaning its chemical composition is similar to the Sun's photosphere.

In other words, it can basically be said to be similar to what the Sun was made out of if all the gas was taken away.

This is important because it is essentially an early image of the solar system's earliest moments. 

But it was only thought that Ryugu might be a CI chondrite. This study sought to narrow down the possibilities and more definitively put the large kilometer-long asteroid in a proper category.

To do this, the researchers, led by cosmochemists Marine Paquet and Frédéric Moynier, analyzed the Ryugu sample brought back indicating the presence of zinc and copper.

This isn't too surprising, as zinc and copper are in other CI chondrites. But what is especially interesting is how the ratios relate to other meteorites.

To figure this out, the scientists behind the study compared the Ryugu sample to other meteorites.

The result showed that the exact isotopic ratios of these copper and zinc in the Ryugu sample were identical to other CI chondrites, but completely different from every other kind of meteorite.

So with that in mind, it seems to firmly identify the Ryugu asteroid as a CI chondrite, but the Ryugu asteroid sample also showed evidence of other elements, specifically chromium and titanium.

These two elements had an isotopic ratio in Ryugu that overlapped with other types of meteorites. However, the zinc and copper ratios are unmistakable.

This matters because the Ryugu asteroid is unique, and not just because asteroid evaluator Asterank put it as the most valuable asteroid in the solar system in terms of cost-effectiveness. 

The Hayabusa2 mission brought back a sample from the asteroid that has been perfectly preserved without being exposed to the atmosphere. For this reason, the sample is untainted and remains the ideal material for studying the early days of the solar system.

But there is a bit more detail to be found regarding the zinc content.

The study found that Ryugu's zinc isotopic composition is relevant for Earth. 

Zinc is a moderately volatile element, meaning it is crucial to the development of life and is one of the most important volatile elements when it comes to studying the makeup of meteorites. 

Now, CI chondrites are rich in zinc and similar elements. The reason for this is believed to be due to where they were formed, with many scientists believing they were formed in the outer asteroid belt. Here are where gas giants exist, which are often filled with volatiles as well.

But what does this have to do with Earth?

Earth also has volatile elements like zinc. However, it is located nowhere near the outer asteroid belt, but is closer to the Sun. 

So how did it get elements like zinc?

Most likely, Earth in its formation managed to accrete a number of volatile materials from the outer solar system. 

And the Ryugu sample, which has high-purity materials ripe for analysis, has these same volatile elements from the early days of the solar system.

It may be that they are the best tools to study these early building blocks of the planet on which we all live.