What is eating ozone? thermal reactions between SO2 and O3: IMPLICATIONS for ICY ENVIRONMENTS

Mark J. Loeffler, Reggie L. Hudson

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Laboratory studies are presented, showing for the first time that thermally driven reactions in solid H2O+SO2+O3 mixtures can occur below 150 K, with the main sulfur-containing product being bisulfate (). Using a technique not previously applied to the low-temperature kinetics of either interstellar or solar-system ice analogs, we estimate an activation energy of 32 kJ mol-1 for formation. These results show that at the temperatures of the Jovian satellites, SO2 and O3 will efficiently react making detection of these molecules in the same vicinity unlikely. Our results also explain why O3 has not been detected on Callisto and why the SO2 concentration on Callisto appears to be highest on that world's leading hemisphere. Furthermore, our results predict that the SO2 concentration on Ganymede will be lowest in the trailing hemisphere, where the concentration of O3 is the highest. Our work suggests that thermal reactions in ices play a much more important role in surface and sub-surface chemistry than generally appreciated, possibly explaining the low abundance of sulfur-containing molecules and the lack of ozone observed in comets and interstellar ices.

Original languageEnglish (US)
Article numberL9
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Dec 10 2016
Externally publishedYes


  • astrochemistry
  • comets: general
  • evolution
  • methods: laboratory: solid state
  • planets and satellites: surfaces
  • radiation mechanisms: thermal

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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