Only 10% of all the xenon that was present as a gas in Earth's primordial atmosphere is estimated to exist in that form today, leaving researchers wondering where the rest went. David Brock and Gary Schrobilgen at McMaster University in Hamilton, Canada, provide a possible solution to the mystery.

They report the synthesis of an elusive Xe compound, xenon dioxide (XeO2). Obtained as a yellow crystal by reacting XeF4 with water at near-ambient conditions, XeO2 shows the spectroscopic features of a square-planar solid. This geometry would let Xe atoms replace some silicon atoms in the lattice of SiO2, one of the most abundant minerals in the Earth's crust.

J. Am. Chem. Soc. doi:10.1021/ja110618g (2011)