Discovery of the Atomic Oxygen Green Line in the Venus Night Airglow
T. G. Slanger,1*
P. C. Cosby,1
D. L. Huestis,1
T. A. Bida2
Green line emission at 557.7 nanometers arising from the
O(1S
1D) transition of atomic oxygen has
been observed on the nightside of Venus with HIRES, the echelle
spectrograph on the W. M. Keck I 10-meter telescope. We also
observe optical emissions of molecular oxygen, consistent with the
spectra from the Venera orbiters, but our green line intensity is so
high that we cannot explain how it could be inconspicuous in the Venera
spectra. An upper limit for the intensity of the O(1D
3P) oxygen red line at 630 nanometers has also been
obtained. The large green/red ratio indicates that the source is not
associated with the Venus ionosphere. An important conclusion is that
observation of the green line in a planetary atmosphere is not an
indicator of an atmosphere rich in molecular oxygen.
1 Aeronomy Group, Molecular Physics Laboratory,
SRI International, Menlo Park, CA 94025, USA.
2 Lowell Observatory, Flagstaff, AZ 86001, USA.
*
To whom correspondence should be addressed. E-mail:
tom.slanger{at}sri.com