Dating of interstellar dust directly with astronomical methods is not possible. Neither is dating based on the decay of long-lived radioactive nuclides, due to current analytical limitations and unknown initial isotopic compositions. Here we present interstellar ages of individual presolar SiC grains from a meteorite. The ages are based on Ne isotopes produced by galactic cosmic rays. Lifetimes of ∼60% of our grains are <3 × 108 y, while at least 8% are >109 y, in line with what is expected for large grains. The former could be the end products of stars originating in an enhanced star formation episode. Presolar grains are the oldest datable solid samples available and provide invaluable insight into the presolar chronology of our galaxy.

We determined interstellar cosmic ray exposure ages of 40 large presolar silicon carbide grains extracted from the Murchison CM2 meteorite. Our ages, based on cosmogenic Ne-21, range from 3.9 ± 1.6 Ma to ∼3 ± 2 Ga before the start of the Solar System ∼4.6 Ga ago. A majority…

Rock, in geology, naturally occurring and coherent aggregate of one or more minerals. Such aggregates constitute the basic unit of which the solid Earth is composed and typically form recognizable and mappable volumes. The three major classes of rock are igneous, sedimentary, and metamorphic rock.