Methane clumped isotopes

Methane clumped isotopes are methane molecules that contain two or more rare isotopes. Methane (CH₄) contains two elements, carbon and hydrogen, each of which has two stable isotopes. For carbon, 98.9% are in the form of carbon-12 (¹²C) and 1.1% are carbon-13 (¹³C); while for hydrogen, 99.99% are in the form of protium (¹H) and 0.01% are deuterium (²H or D). Carbon-13 (¹³C) and deuterium (²H or D) are rare isotopes in methane molecules. The abundance of the clumped isotopes provides information independent from the traditional carbon or hydrogen isotope composition of methane molecules.