Thomas A. Bida
W. M. Keck Observatory, Kamuela, HI 96743
(now at Lowell Observatory, Flagstaff, AZ)
The observations were made just before sunrise on the morning of November 20, 1999 at the Keck 1 Telescope on Mauna Kea, Hawaii, with the slit positioned on the night side of Venus as shown by the small rectangle.
The inset shows the spectrum of atomic oxygen "green line" emission from the atmospheres of Earth (left peak) and Venus (right peak) at different positions along the slit. The 1 Angstrom wavelength scale extends from 5577 to 5578 Angstroms. The Venus emission is "red shifted" due the relative motion of Venus away from the Earth. The magnitude of the Venus peak increases as the field of view of the telescope approaches the edge of the planet, at which point the greatest volume of atmosphere is observed. The intensity falls as the field of view passes into empty space.
Atomic oxygen emissions are well known on Earth, but have never been observed previously in the nightglow of another planet.
The day side and night side of Venus are shown from a computer simulation, based on a Mariner 10 image, generated at the JPL website http://space.jpl.nasa.gov/ [Courtesy Jet Propulsion Laboratory. Copyright (c) California Institute of Technology, Pasadena, CA. All rights reserved. Based on government-sponsored research under contract NAS7-1407.]
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