O/O2 emissions in the Venus nightglow

► Emission from the O(1S) atom can be an important feature of the Venus nightglow. ► In 1999, an O(1S) green line intensity of 150 R was found. ► Ground-based studies suggest that the emission is correlated with the solar cycle. ► Measurements in 2010 have failed to detect the O(1S) green line. ► These observations are consistent with an ionospheric Venus green line source.