It is known as the "Allende meteorite." It fell in 1969. The Solar System is about 4.6 billion years old. But in this meteorite there are grains dating between 5,000 and 7,000 million years. The study was published in the journal «Nature Astronomy». That is, material older than the Sun and all our cosmic neighborhood. The meteorite was billions of years wandering through space. the meteor trip older than the sun.
It is not the first time that these presolar grains are in a meteorite. Another space rock dropped in Australia in the same year also contained this material. The studied fragment of the Allende meteorite, known as "Curious Marie", has a special feature. It contradicts everything that was known about long-distance interstellar objects. Traces of silicon carbide (SiC) were found. "The surprising thing is the fact that presolar grains are present here," says Olga Pravdivtseva, a physical and cosmochemical researcher responsible for the study. "Following our current understanding of the formation of the Solar System, presolar grains could not survive in the environment where such meteorites form."
‘Curious Marie’ is a notable example of an “inclusion” or a portion within a meteorite, called calcium-aluminum-rich (CAI) inclusion. These objects are some of the first to condense in the solar nebula. They help cosmochemists define the age of the Solar System. For the new work, Pravdivtseva and his team used isotopic noble gas signatures to show that presolar silicon carbide (SiC) grains are present in Curious Marie.
Light on the past
That is important. Presolar grains are generally considered too fragile to withstand the high temperature conditions that existed near the birth of our Sun.
But not all CAIs were formed in the same way. "This informs us about the environment in the solar nebula in the condensation of the first solid materials," says Pravdivtseva. It is part of the McDonnell Center for Space Sciences at the University of Washington. "That SiC has not been completely destroyed in Curious Marie can help us understand this environment a little better," he says.
The researchers are wondering something. How did another star's silicon carbide reach these primordial solids like Allende, the meteorite older than the Sun? The fact that it did means that we must rethink some things about chemistry at the beginning of our environment. "Although the CAIs, the solid solids of the Solar System, have been extensively studied, there are still questions about the nature and origin of the isotopic anomalies that they carry, their distribution between primitive meteorological classes and the relations with other meteorological components," write the researchers.