Near‐IR oxygen nightglow observed by VIRTIS in the Venus upper atmosphere

The oxygen nightglow at Venus has been intensively studied from ground observations since its discovery in spectra obtained on 1975 (Connes et al, 1979) during the inferior conjunction periods, with some glimpses from space during the flybys of the Galileo (NIMS) mission. Here we discuss the vertical profile of the oxygen nightglow in limb view geometry as observed by VIRTIS, emphasizing the vertical transport more than the horizontal motion which is more extensively studied in another paper of this issue (Hueso et al, 2008). We will also show some results coming from nadir observation geometry, providing an extended view of how the vertical transport is locally distributed. Both the (0-0) band at 1.27 μm and the (0-1) band at 1.58 μm are detected and a ratio of transition probabilities A00/A01 = 63±6 is inferred. We have analyzed up to now 31 cubes for 13 orbits, covering latitude range from 10 to 75° N. The vertical distribution of the O2 emissions are very similar and their peak is typically found to be at 98±2 km with some exceptions. Cases where the peak is significantly higher in altitude, at about 103 km, are present and other cases with a double peak exist as well. No obvious geographical dependence has been found for the peak altitude and emission strength in long term (days or weeks), while more regular trends versus local time or latitude are observed in a short term within the same orbit.