A layer of ozone detected in the nightside upper atmosphere of Venus

To date, ozone has only been identified in the atmospheres of Earth and Mars. This study reports the first detection of ozone in the atmosphere of Venus by the SPICAV ultraviolet instrument onboard the Venus Express spacecraft. Venusian ozone is characterized by a vertically confined and horizontally variable layer residing in the thermosphere at a mean altitude of 100 km, with local concentrations of the order of 107–108 molecules cm−3. The observed ozone concentrations are consistent with values expected for a chlorine-catalyzed destruction scheme, indicating that the key chemical reactions operating in Earth’s upper stratosphere may also operate on Venus.

► Ozone has been detected for the first time in the atmosphere of Venus. ► Ozone accounts for a tenuous layer in the upper atmosphere of Venus nightside. ► Observed ozone concentrations are consistent with chlorine-catalyzed chemistry. ► This discovery provides additional constraints for the search of biomarkers on extraterrestrial planets.