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Ancient meteorites preserve building blocks of early solar system - Space.com
Oct 13, 2021 1 min, 30 secs

Some meteorites contain grains older than the solar system.

These grains, which are older than the solar system itself, formed in ancient stars that died before our sun's birth.

Similar stars still exist in the universe and the analysis of these presolar grains provides an interesting glimpse into the stars' chemistry.

In the Murchinson meteorite, grains of rock older than the solar system are embedded in younger material.

"These grains are made of silicon carbide, that is silicon and carbon atoms," Liu said.

"But silicon carbide doesn't naturally form in our solar system because we have a lot of oxygen around and all these carbon atoms would bond with oxygen first to form carbon oxide molecules.".

The most likely origin of these grains are the carbon stars, bright red giant stars whose atmospheres contain more carbon than oxygen, Liu said.

But these presolar grains have carbon 12 to carbon 13 ratios ranging from 2 to 200, which results from fusion reactions in their parent stars.".

Astronomers were especially interested whether the isotopic compositions found in these grains matched what observations revealed about carbon stars.

One reason could be that these stars, in fact, were not the birthplace of these grains, Liu said.

"The past measurements were showing much lower carbon and nitrogen isotope ratios in those grains," Liu said.

As part of this technique, they first dissolved pieces of the Murchinson meteorite in acid until they were left only with the silicon carbide grains.

This confirmed Liu's original suspicion and showed that not only did these grains most likely come from carbon stars but also that they can now be used to help scientists advance their understanding of these types of stars.

"Indeed, the 'strange' nitrogen isotopic ratios of presolar silicon carbide grains have been in the last two decades a remarkable source of concern.

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