The researchers recommend determining the uneven distribution of short-lived isotopes to improve the accuracy and reliability of determining the ages of meteorites and planetary materials.
An international team of astrophysicists established, at approximately 4.566 million years, the precise isotopic age of the lead-207 – lead-206 decay system in the Erg Chech 002 meteorite. In turn, This result allowed us to demonstrate a heterogeneous distribution of aluminum-26 (26Al). This short-lived radionuclide was an important heat source for early planetary melt in the protoplanetary disk of our solar system and serves as a high-resolution relative chronometer.
Erg Chech 002 is an andesitic achondrite found in May 2020 in the Erg Chech region of the Sahara Desert, Algeria. It is a stony meteorite with large distinctive greenish crystals, one of the oldest known to date. Establishing the age of Erg Chech 002 using lead provided the opportunity to further explore the initial distribution of aluminum-26 in the precursor molecular cloud or protoplanetary disk of the early solar system.
“The presence of aluminum-26 (half-life: 705 million years) in the early solar system, and its possible role as a heat source for the melting of planets and asteroids and early metamorphism, was predicted more than 60 years ago,” the scientists noted in a paper published last week in Nature Communications.
A heterogeneously distributed isotope
The age established by lead isotopes in combination with published data from the aluminum-26-magnesium-26 (26Al/27Al) system, for this meteorite and other achondrites, revealed that the initial 26Al/27Al in the source material of this achondrite it was noticeably higher than in other well-preserved and accurately dated achondrites. The researchers demonstrated the spatial heterogeneity of the 26Al isotope by a factor of 3-4 in the protosolar nebula. Scientists consider that this heterogeneity is probably associated with the late fall of stellar materials with newly synthesized radionuclides.
“Meteorite chronology studies should be cautious and adopt a generalized approach to dating with short-lived isotopes that takes into account their uneven distribution to improve the accuracy and reliability of determining the ages of meteorites and planetary materials” , the researchers stressed.