Spectra of Venus and Jupiter From 1300 to 3200 Å

R. C. Anderson University of Florida, Gainesville

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J. G. Pipes University of Florida, Gainesville

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A. L. Broadfoot Kilt Peak National Observatory, Tucson, Ariz.

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L. Wallace Kilt Peak National Observatory, Tucson, Ariz.

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Abstract

The results of two Aerobee rocket flights are reported. One obtained spectra of Venus from 3200 to 1900 Å at 16.5 Å resolution and the other spectra of Jupiter from 32M to 1800 Å at 28 Å resolution. The spectra of both planets are of much higher statistical accuracy than those that have been obtained previously. The peculiarities indicated by the previous observations are not confirmed. In particular, there does not appear to be an absorption feature in the Jupiter spectrum at 2600 Å or an ozone absorption in the Venus spectrum.

Two extreme models are used to interpret the data: the reflecting layer model and the cloud model. We find that the CO2 abundances for Venus and the H2 abundances for Jupiter, deduced with the reflecting layer model from observations in the red and IR parts of the spectrum, are much ton large to be compatible with the UV albedos. In terms of the cloud model, the albedos of both planets down to 2200 Å are the result of the decreasing single scattering albedo of the cloud particles and the increasing Rayleigh scattering. These two effects produce an almost constant geometric albedo from 2800 to 2200 Å. Below 2200 Å, the Venus albedo drops sharply due to CO2, absorption; the Jupiter albedo drops off by a factor of 4 due to NH3 absorption, an unidentified absorber, a decrease in the cloud particle albedo, or Borne combination of these effects.

Abstract

The results of two Aerobee rocket flights are reported. One obtained spectra of Venus from 3200 to 1900 Å at 16.5 Å resolution and the other spectra of Jupiter from 32M to 1800 Å at 28 Å resolution. The spectra of both planets are of much higher statistical accuracy than those that have been obtained previously. The peculiarities indicated by the previous observations are not confirmed. In particular, there does not appear to be an absorption feature in the Jupiter spectrum at 2600 Å or an ozone absorption in the Venus spectrum.

Two extreme models are used to interpret the data: the reflecting layer model and the cloud model. We find that the CO2 abundances for Venus and the H2 abundances for Jupiter, deduced with the reflecting layer model from observations in the red and IR parts of the spectrum, are much ton large to be compatible with the UV albedos. In terms of the cloud model, the albedos of both planets down to 2200 Å are the result of the decreasing single scattering albedo of the cloud particles and the increasing Rayleigh scattering. These two effects produce an almost constant geometric albedo from 2800 to 2200 Å. Below 2200 Å, the Venus albedo drops sharply due to CO2, absorption; the Jupiter albedo drops off by a factor of 4 due to NH3 absorption, an unidentified absorber, a decrease in the cloud particle albedo, or Borne combination of these effects.

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