Lab tests hint at where xenon hides out.

The article discusses new experiments conducted at high temperatures and pressures which may explain the puzzlingly low concentration of xenon gas in the atmosphere. Under conditions normally found at Earth's surface, atoms of xenon don't bond with other atoms, a trait common to the other elements known as inert gases, including neon, argon, and krypton. But atmospheric concentrations of the gas on Mars and Earth are one-twentieth of what would be the expected values from its abundance in the universe, says Chrystèle Sanloup, a geophysicist at Pierre and Marie Curie University in Paris.