Trapped gases
Trapped gases are noble gases incorporated into a meteorite when it formed or during later events, rather than made inside it.
Noble gases in meteorites that were not produced inside the rock, by decay or cosmic rays, are called trapped gases. They were captured as the rock or its components formed, or during events such as impacts.
Several trapped components are recognised. The solar component, from the solar wind, is found in regolith breccias. The so-called planetary or Q component is held by carbon-rich carriers in primitive chondrites and has its own distinctive isotope pattern. Presolar grains carry exotic gases from other stars, such as xenon with unusual heavy and light isotope patterns first found in nanodiamonds.
Shock events can trap gases too. Melt glass in Martian shergottites caught samples of the Martian atmosphere, with nitrogen and noble gas ratios that match Viking measurements and include a much higher argon-40 to argon-36 ratio than Earth's air. Distinguishing these trapped components is a detective task that reveals where a meteorite's material originated.
Related terms
Level: Expert Advanced