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Record 43 of 13834
High-Resolution Spectroscopy of Mars: Recent Results and Implications for Atmospheric Evolution
Author and Affiliation:
Krasnopolsky, V. A.(NASA Goddard Space Flight Center, Greenbelt, MD United States)
Owen, T. C.(Hawaii Univ., Inst. for Astronomy, Honolulu, HI United States)
Maillard, J. P.(Institute d'Astrophysique de Paris, Paris France)
Abstract: It is believed that Earth, Venus, and Mars were formed by the same rocky and icy planetesimals, which resembled meteorites and comets in their composition, respectively. These planets are thus expected to have initially had the same chemical and isotope composition. Scaling the mass of the terrestrial ocean by the planetary mass ratio, the expected initial H2O abundance on Mars is a layer of about 1 km thick. Scaling the abundance of CO2 on Venus, the expected initial CO2 abundance on Mars is 15 bars. Evidently, significant parts of the initial H2O and CO2 abundances have been lost. Intense meteorite impact erosion and hydrodynamic escape of hydrogen (which could drag to escape more heavy species) were dominant loss processes in the first 0.8 Byr. Later, atmospheric sputtering by O+ ions resulted in the dissociation of CO2 and massive losses of O, C, and H. Formation of carbonates also reduced CO2 to its present abundance which currently exists in the atmosphere, on the polar caps, and is absorbed by regolith. Water loss is currently due to thermal escape of H and nonthermal escape of O, both formed by photodissociation of H2O. All loss processes resulted in fractionation of the H, O, and C isotopes. Therefore, the current isotope ratios in H2O and CO2 are clues to the history of volatiles on Mars. There are three tools to study H2O and CO2 isotopes in the martian atmosphere: (i) mass spectrometry from landing probes, (ii) analyses of Mars' gases trapped in the SNC meteorites which were ejected from Mars, and (iii) high-resolution spectroscopy of the H2O andCO2 bands. Method (i) is the best but is the most expensive. Mass spectrometers to be used should be designed for high-precision isotope measurements. Method (ii) makes it possible to reach an uncertainty +/- 0.1%. However, the obtained results are affected by some uncontrolled interactions: isotope fractionations of (1) trapped gases and (2) those released in pyrolysis, (3) contribution of the impactor, isotope exchanges (4) in the terrestrial environment and (5) with the host rock during pyrolysis. Therefore, the spectroscopic data are of great interest, though their formal accuracy is lower. High-resolution spectroscopy is also a tool to study the current atmosphere of Mars by mapping of some photochemically important species and searching for some minor constituents and their variations. Additional information is contained in the original extended abstract.
Publication Date: Jul 01, 1999
Document ID:
20000110388
(Acquired Nov 17, 2000)
Subject Category: INORGANIC, ORGANIC AND PHYSICAL CHEMISTRY
Document Type: Conference Paper
Publication Information: The Fifth International Conference on Mars; (LPI-Contrib-972); (SEE 20000110269)
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD United States
Description: In English; CD-ROM contains the entire conference proceedings presented in PDF format
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: ATMOSPHERIC COMPOSITION; MARS (PLANET); MARS ATMOSPHERE; PLANETARY EVOLUTION; GAS COMPOSITION; COSMOCHEMISTRY; METEORITIC COMPOSITION; HIGH RESOLUTION; PHOTOCHEMICAL REACTIONS; TERRESTRIAL PLANETS; WATER; MASS SPECTROSCOPY
Availability Notes: Abstract Only; Available from STI Support Services only as part of the entire parent document
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