When Ryland discovers that the cylinder transferred from the Blip-A is made of xenon, he is initially baffled and runs his test multiple times to confirm this “wacky” result: “It doesn’t react with anything. It doesn’t form bonds with anything. And it’s a gas at room temperature. But somehow it’s part of this solid material?” 08.135 Eventually he is forced to accept that there is no fault with his spectrometer (for an introduction to spectroscopy, see #58) and that the cylinder is made of solid xenon. Throughout Project Hail Mary, xenonite (as Ryland dubs this “weird alien compound” 08.177) is used for a variety of practical applications.

Xenon is a chemical element with the atomic number 54. It is found in group 18 of the periodic table, the noble gases, alongside other “inert” elements including neon, argon, and krypton. Xenon is generally considered unreactive, as Ryland recalls, but it can undergo chemical reactions under the right conditions.

In 1962, chemist Neil Bartlett at the University of British Columbia produced xenon hexafluoroplatinate, the first noble gas compound, demonstrating that this “inert” element was not quite so inert as previously thought. Note: there exists some debate about whether pure xenon hexafluoroplatinate is the exact substance produced by Bartlett in 1962, but he nevertheless is credited with discovering that xenon can undergo chemical reactions.

Many additional xenon compounds have been discovered since 1962, including xenon difluoride (pictured below) and xenon trioxide, a powerful and explosive oxidizing agent. Krypton and radon can also form compounds, though their instability and radioactivity make them more difficult to study.