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Record 22 of 254
(abstract) Odd Hydrogen in the Atmospheres of Earth and Mars
External Online Source: hdl:2014/34505
Author and Affiliation:
Nair, Hari
Allen, Mark
Yung, Yuk L.
Abstract: The Martian atmosphere has many features in common with the terrestrial mesosphere. Both share similar pressure and temperature ranges, and much of the same chemistry operates in each. For example, the radical species H, OH, and H(sub 2)O, which comprise the odd hydrogen family, are of central importance in the catalytic destruction of CO and O(sub 3) in both atmospheres. The inclusion of recent chemical kinetics data, specifically temperature dependent CO(sub 2) absorption cross-sections, into our one dimensional photochemical model of the Martial atmosphere shows that oxidation of CO by odd hydrogen is too efficient. The incorporation of smaller cross sections for CO(sub 2) leads to an enhanced photolysis rate of water vapor, increasing odd hydrogen to the point where the predicted mixing ratio of CO in our model is substantially less than the observed value of 6.5 x 10(sup -4). Interestingly, most photochemical models of the terrestrial mesosphere underestimate the CO and O(sub 3) densities using currently accepted photodissociation and kinetic rate coefficients. This has also been attributed to an overabundance of odd hydrogen in the models. We shall show that agreement between models and observations of CO in the Martian atmosphere as well as of CO and O(sub 3) in the terrestrial mesosphere can be achieved by revising the rate constants for the reactions OH + HO(sub 2) and CO + OH within their published uncertainties. The fact that similar revisions alleviate discrepancies in both the terrestrial and Martian atmospheres warrants a re-evaluation of these key rate constants at the appropriate temperatures and pressures.
Publication Date: Jun 06, 1994
Document ID:
20060038512
(Acquired Sep 14, 2006)
Subject Category: LUNAR AND PLANETARY SCIENCE AND EXPLORATION
Document Type: Preprint
Financial Sponsor: Jet Propulsion Lab., California Inst. of Tech.; Pasadena, CA, United States
Description: In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: ABSORPTION CROSS SECTIONS; ATMOSPHERIC MODELS; CARBON; CARBON MONOXIDE; COEFFICIENTS; CONSTANTS; DESTRUCTION; DIOXIDES; EARTH ATMOSPHERE; GAS PRESSURE; HYDROGEN; MARS (PLANET); MARS ATMOSPHERE; MESOSPHERE; MIXING RATIOS; OXIDATION; OZONE; PHOTOCHEMICAL REACTIONS; PHOTODISSOCIATION; PHOTOLYSIS; RADICALS; REACTION KINETICS; TEMPERATURE DEPENDENCE; WATER SPLITTING; WATER VAPOR
Other Descriptors: DIOXIDE OZONE ODD HYDROGEN FAMILY PRESSURE TEMPERATURE PHOTODISSOCIATION; PHOTOLYSIS; MARTIAN ATMOSPHERE TERRESTRIAL MESOSPHERE HYDROGEN CARBON MONOXIDE CARBON
Availability Source: Other Sources
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