Argon (element)

Argon is a chemical element.

Argon is commonly found in the form of gas in the atmospheres of Class L marginal planets across the galaxy in combination with oxygen. 

Argon became unstable when exposed continuously to zeton radiation, causing it to ionize or to recombine with other elements lower on the periodic table. This was the case on the planet Epsilon Delta IV, which had an atmosphere of slightly less than two percent argon, as compared to Earth's one percent.