On September 28, 1969, a large fireball could be seen in the sky in Victoria, southeast of Australia, which divided into three fragments before disappearing. Shortly after, an impact was felt. It was the Murchison meteorite, from which up to 100 kilos of material were recovered. Since then organic compounds and sugars have been found in these rocks that have reaffirmed the theory that the essential compounds for life to arise on Earth came from space aboard meteorites. Now, a new study reveals that these rocks contain even more surprising things.
The largest fragment of the Murchison meteorite is in the Field Museum in Chicago. There, Philipp Heck’s team has analyzed a portion of this celestial body concentrating on 40 grains of silicon carbide, a material with a hardness similar to that of diamond. Each piece measures just a few microns, that is, it is about a thousand times smaller than a millimeter, but it contains information that dates back to before the Earth, the Sun and the rest of the solar system existed.
The researchers have analyzed the changes in silicon carbide produced by the impact of cosmic rays whose particles are capable of changing the atomic composition of the original material and which, due to their frequency, can be used as a clock that estimates the age of the sample. .
The results show that most of the analyzed grains are 300 million years older than the solar system, which formed about 4.6 billion years ago, and that some of them are 1 billion years older, the authors of the work highlight, published today in the magazine Proceedings of the US National Academy of Sciences.
“This is the oldest material ever found,” explains Heck in a press release. The expert defines the material analyzed as “authentic stardust” and highlights that its analysis allows us to clarify how the stars were formed in our galaxy, the Milky Way.
According to his team, the tiny “star fragments” analyzed come from a star that was born about 7 billion years ago during a period of intense star formation. That material was spit out by its star. First it wandered alone through interstellar space and then it was entombed within a body of rock, where it remained intact for billions of years. That rock or part of it was attracted by the force of Earth’s gravity, entered the atmosphere and decomposed into all the fragments of the Murchison meteorite that fell on Australia in 1969. Having found these compounds is a milestone, since most of the stardust that remains deposited in meteorites is destroyed by the pressure. Only about 5% of known meteorites contain material of this type and its abundance does not usually exceed a few parts per million.
This material points to the origin of the solar system even before it existed. “Silicon carbide grains are among the most refractory and resistant materials that form meteorites called carbonaceous chondrites, like the Murchison meteorite,” explains Josep M. Trigo, an expert in meteorites at the Institute of Space Sciences (IEEC-CSIC). , in Barcelona. “The interest of this work is that the authors show that most of this type of presolar grains formed in a type of star known as the asymptotic branch of the giants. This reaffirms a previous study by our group that our Sun could have formed in the vicinity of stars of this type”, he highlights.