Thursday, March 30

Stardust in meteorites, key to better understanding the history of the Universe

The meteorite NWA801, found in Morocco. / jon taylor

These extraterrestrial specks, as small as viruses, are the oldest solid materials on Earth, and predate the creation of the Solar System

Elena Martin Lopez

Meteorites, in general, do not have a good reputation. But, leaving aside their participation in the extinction of the dinosaurs, these rocks hide very valuable information that is difficult to appreciate with the naked eye. One of its compounds, stardust, is what has been investigated by an international team of scientists, in which the University of Cádiz has participated, in order to shed more light on the history of the Universe.

They have defined the chemical composition of nine presolar grains (specks of stardust) contained in two meteorites. On the one hand, the Isheyevo meteorite, found in Russia, and on the other, the NWA801, from Morocco. “Presolar grains are one of the oldest solid materials on our planet, even prior to the formation of the Solar System 4.5 billion years ago,” explains Luc Lajaunie, a researcher at the University of Cádiz and co-author of the study. That is, they are something like a fossil of the activity of stars in space more than 4,500 million years ago, since some of the presolar grains have remained unchanged since their formation.

Finding these materials as they were originally has been a challenge, since meteorites can suffer many alterations due to possible impacts with other celestial bodies that float in space, the heat of the atmosphere and their subsequent collision with the surface of the planet, and the very environmental conditions to which they are exposed until they are found and taken to the laboratory.

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Luc Lajaunie shows the microscope located in the Electron Microscopy Division of the University of Cádiz.

two types of stars

After identifying and isolating the presolar grains of both meteorites, whose size is similar to that of a virus (100 nanometers), which was possible thanks to the collaboration of the Academia Sinica (Taiwan), the Planetary Sciences Division of the Research Laboratory of Physics (India) and the universities of Curtin (Australia) and Copenhagen (Denmark), researchers from the University of Cádiz took over. His work focused on analyzing the chemical composition and physical structure of the pressor grains through a unique microscope in Spain, located in the Electron Microscopy Division of said academic institution.

What they found is that the stardust contains silicates, a mineral composition similar to terrestrial quartz that is the product of the death of two types of stars, supernovae and red giants. When these stars stop shining, they give rise to explosions and solar winds, respectively, which enrich space with stardust. Later, these particles agglomerate and form new celestial bodies, and thus, for example, the elements of the Solar System (planets, satellites…) were created.

How are stars born and die?

Of what they found, Lajaunie says: “Working with silicates allows us to better understand what cosmic events of the death of stars are like and what they produce. For example, that fluorine originates from these two cosmic events. In addition, although the presolar grains come from the two types of stars mentioned, their chemical compositions are very similar. What is most striking is that materials that we find on Earth, such as meteorites, were created long before it existed and can give us information on how our planet was formed”, celebrates Lajaunie. The study has been published in the scientific journal ‘The Astronomical Journal’.

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