Semiperiodic variations in CO2 abundance on Venus |
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| Authors: | Edwin S Barker Michael A Perry |
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| Institution: | The University of Texas, McDonald Observatory, Fort Davis, TX 79734, USA |
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| Abstract: | Photoelectric spectral scans of the P branch of the 8689 Å CO2 band on Venus were made using the 107-inch coude scanner during seven observing periods in the past 2 years. The relative CO2 line strength was determined for each scan, then normalized to remove the spatial variations leaving only temporal variations.The 4-day periodicity in the relative CO2 line strength noted by Young et al. (1973) is not unique; we do confirm their 4-day periodicity in August 1973. Four other observing periods rule out a 4-day periodicity.A definite North-South asymmetry in the relative CO2 line strength is noted during 1973, in most cases with the same periodicity present in both hemispheres. When the slit positions are referred to the equator of Venus, particularly near inferior conjunction, the large asymmetrics between the slit positions can be explained by a greater CO2 line strength over the polar regions and weaker over the equatorial latitudes. The amplitude of variation of each position on the crescent is much greater near inferior conjunction either because we are sampling a smaller area on the planet or because the upper atmospheric abundance is more sensitive to the mechanism causing the variation in the smaller regions sampled at inferior conjunction.Simultaneous H2O measurementsduring several of the observing runs indicate a lack of correlation in the relative CO2 line strengths and the H2O abundance. |
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