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Published 1965 | Published
Journal Article Open

On the interpretation of strong CO_2 absorption bands in the spectrum of Mars

Abstract

The determination of the atmospheric pressure at the surface of Mars by spectroscopic means is based on the comparison of broad-band measurements of strong CO_2 bands in the instrumental infrared with the intensity of weak lines of the same molecule at lower wavelengths (Kaplan, Munch and Spinrad, 1964). The absorption in a strong band, formed by non-overlapping pressure-broadened lines, is asymptotically proportional to the product (wp) between the amount of absorber w and the pressure p of the broadening gas. The weak line absorption, in contrast, depends only on the net amount of absorber. At present, it appears that much of the uncertainty affecting estimates of the pressure in Mars' atmosphere arises from the difficulties associated with the measurement of the equivalent widths of the very weak lines (Chamberlain and Hunten, 1965). In addition, the interpretation of the absorption by strong bands is affected by uncertainties arising from estimating the level of a "continuum" from which the absorption is measured and the procedures followed to allow for the CO_2 absorption in the earth's atmosphere.

Additional Information

© 1965 Lowell Observatory. Work supported in part by NASA Grant NsG 426.

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August 19, 2023
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