A COUPLED SOIL ATMOSPHERE MODEL OF H2O2 ON MARS

被引:111
作者
BULLOCK, MA [1 ]
STOKER, CR [1 ]
MCKAY, CP [1 ]
ZENT, AP [1 ]
机构
[1] NASA,AMES RES CTR,DIV SPACE SCI,MOFFETT FIELD,CA 94035
关键词
D O I
10.1006/icar.1994.1012
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The Viking Gas Chromatograph Mass Spectrometer failed to detect organic compounds on Mars, and both the Viking Labeled Release and the Viking Gas Exchange experiments indicated a reactive soil surface. These results have led to the widespread belief that there are oxidants in the martian soil. Since H2O2 is produced by photochemical processes in the atmosphere of Mars, and has been shown in the laboratory to reproduce closely the Viking LR results, it is a likely candidate for a martian soil oxidant. Here, we report on the results of a coupled soil/atmosphere transport model for H2O2 on Mars. Upon diffusing into the soil, its concentration is determined by the extent to which it is adsorbed and by the rate at which it is catalytically destroyed. An analytical model for calculating the distribution of H2O2 in the martian atmosphere and soil is developed. The concentration of H2O2 in the soil is shown to go to zero at a finite depth, a consequence of the nonlinear soil diffusion equation. The model is parameterized in terms of an unknown quantity, the lifetime of H2O2 against heterogeneous catalytic destruction in the soil. Calculated concentrations are compared with a H2O2 concentration of 30 nmoles/cm3, inferred from the Viking Labeled Release experiment. A significant result of this model is that for a wide range of H2O2 lifetimes (up to 10(5) years), the extinction depth was found to be less than 3 m. The maximum possible concentration in the top 4 cm is calculated to be approximately 240 nmoles/cm3, achieved with lifetimes of greater than 1000 years. Concentrations higher than 30 nmoles/cm3 require lifetimes of greater than 4.3 terrestrial years. For a wide range of H2O2 lifetimes, it was found that the atmospheric concentration is only weakly coupled with soil loss processes. Losses to the soil become significant only when lifetimes are less than a few hours. If there are depths below which H2O2 is not transported, it is plausible that organic compounds, protected from an oxidizing environment, may still exist. They would have been deposited by meteors, or be the organic remains of past life. (C) 1994 Academic Press, Inc.
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页码:142 / 154
页数:13
相关论文
共 42 条
[1]   MODELING OF SOIL PORES AS TUBES USING GAS PERMEABILITIES, GAS DIFFUSIVITIES AND WATER RELEASE [J].
BALL, BC .
JOURNAL OF SOIL SCIENCE, 1981, 32 (04) :465-&
[2]   THE CASE FOR A MARTIAN ORIGIN OF THE SHERGOTTITES - NITROGEN AND NOBLE-GASES IN EETA-79001 [J].
BECKER, RH ;
PEPIN, RO .
EARTH AND PLANETARY SCIENCE LETTERS, 1984, 69 (02) :225-242
[3]  
Biemann K., 1977, Journal of Geophysical Research, V82, P4641, DOI 10.1029/JS082i028p04641
[4]   IMPLICATIONS AND LIMITATIONS OF THE FINDINGS OF THE VIKING ORGANIC-ANALYSIS EXPERIMENT [J].
BIEMANN, K .
JOURNAL OF MOLECULAR EVOLUTION, 1979, 14 (1-3) :65-70
[5]   NOBLE-GAS CONTENTS OF SHERGOTTITES AND IMPLICATIONS FOR THE MARTIAN ORIGIN OF SNC METEORITES [J].
BOGARD, DD ;
NYQUIST, LE ;
JOHNSON, P .
GEOCHIMICA ET COSMOCHIMICA ACTA, 1984, 48 (09) :1723-1739
[6]   COMETARY DELIVERY OF ORGANIC-MOLECULES TO THE EARLY EARTH [J].
CHYBA, CF ;
THOMAS, PJ ;
BROOKSHAW, L ;
SAGAN, C .
SCIENCE, 1990, 249 (4967) :366-373
[7]  
CHYBA CF, 1989, LUNAR PLANET SCI C, V20, P157
[8]   THE STABILITY OF GROUND ICE IN THE EQUATORIAL REGION OF MARS [J].
CLIFFORD, SM ;
HILLEL, D .
JOURNAL OF GEOPHYSICAL RESEARCH, 1983, 88 (NB3) :2456-2474
[9]  
COULTER DR, 1987, JPL D4657 TECH REP
[10]  
DEMORE WB, 1985, JPL PUBL, V8537