GEOCHEMISTRY:
A Stranger in Paradise
Paul F. McMillan
Chemical wisdom has it that the "noble" gases such as xenon are chemically unreactive. Yet xenon appears to be depleted in the atmospheres of Mars and Earth. Could xenon be forming chemical compounds with the minerals in the crusts of these planets? In his Perspective, McMillan discusses results reported in the same issue by Sanloup et al. in which optical spectroscopy and x-ray diffraction have been used to show that xenon can react with natural silicate species to form compounds at the pressure and temperature conditions found in Earth's crust. Under the right conditions, such high-pressure solid-state chemistry may extend to other noble gases.
The author is in the Department of Chemistry and Materials Chemistry Centre, University College London, London WC1H 0AJ,UK, and the Davy-Faraday Research Laboratory, Royal Institution, London WBX 4BS, UK. E-mail: p.f.mcmillan{at}ucl.ac.uk