One in a sextillion: Scientists directly detect one of Earth’s rarest argon isotopes

Scientists directly detected ultra-rare argon-42 in Earth’s atmosphere using laser-based Atom Trap Trace Analysis.

By pre-enriching an argon sample, they counted 204 argon-42 atoms over 43 days and estimated an abundance of about 6.1 × 10^-21.

The result sets a new extreme for isotope detection and could improve environmental dating and dark matter experiments by reducing background noise.