Io's atmosphere from microwave detection of so2

ABSTRACT SINCE the detection by Pioneer 10 of an ionosphere1 around Io, this moon of Jupiter has been known to possess a tenuous atmosphere. The local observation of gaseous SO2 and the

upper limits on the concentrations of other gases deduced from Voyager data2, together with the identification of SO2 frost or adsorbate at the surface3,4 and upper limits on the global

amount of atmospheric SO2 (refs 5–8), have led to several classes of models for Io's atmosphere9. Here we report the microwave detection of SO2 at 222 GHz, which constitutes the first

direct global observation of Io's neutral atmosphere. The observations imply an SO2 surface pressure of 4–35 nanobars, covering 3–15% of the surface on both leading and trailing sides

of Io when illuminated by the Sun. This supports atmospheric models in which the partial pressure of SO2 at the surface is determined by the local surface temperature8, favouring, in

particular, the 'albedo cold-trap' models10,11. Our failure to detect H2S at 169 GHz suggests that the pressure of this gas is probably below 10 −10 bar. Our results, taken

together with the Pioneer ionospheric data, suggest that an atmospheric gas other than SO2 is present. We propose that the locally buffered SO2 atmosphere coexists with a background

atmosphere of oxygen with a partial surface pressure of ∼20 nanobars. Access through your institution Buy or subscribe This is a preview of subscription content, access via your institution

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about institutional subscriptions * Read our FAQs * Contact customer support SIMILAR CONTENT BEING VIEWED BY OTHERS A SUBLIMATED WATER ATMOSPHERE ON GANYMEDE DETECTED FROM HUBBLE SPACE

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1147–1151 (1972). Article  ADS  Google Scholar  Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Observatoire de Paris, 92195, Meudon, France Emmanuel Lellouch & 

Thérèse Encrenaz * National Optical Astronomy Observatories, Tucson, Arizona, 85726, USA Michael Belton * Radio-Astronomy Department, University of California, Berkeley, California, 94720,

USA Imke de Pater * Jet Propulsion Laboratory, Pasadena, California, 91109, USA Samuel Gulkis Authors * Emmanuel Lellouch View author publications You can also search for this author

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Io's atmosphere from microwave detection of SO2. _Nature_ 346, 639–641 (1990). https://doi.org/10.1038/346639a0 Download citation * Received: 12 April 1990 * Accepted: 27 June 1990 *

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