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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars
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Detection of oxygen isotopic anomaly in terrestrial atmospheric carbonates and its implications to Mars

机译:陆地大气碳酸盐中氧同位素异常的探测及其对火星的影响

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The debate of life on Mars centers around the source of the globular, micrometer-sized mineral carbonates in the ALH84001 meteorite; consequently, the identification of Martian processes that form carbonates is critical. This paper reports a previously undescribed carbonate formation process that occurs on Earth and, likely, on Mars. We identified micrometer-sized carbonates in terrestrial aerosols that possess excess 17O (0.4-3.9‰). The unique O-isotopic composition mechanistically describes the atmospheric heterogeneous chemical reaction on aerosol surfaces. Concomitant laboratory experiments define the transfer of ozone isotopic anomaly to carbonates via hydrogen peroxide formation when O3 reacts with surface adsorbed water. This previously unidentified chemical reaction scenario provides an explanation for production of the isotopically anomalous carbonates found in the SNC (shergottites, nakhlaites, chassignites) Martian meteorites and terrestrial atmospheric carbonates. The anomalous hydrogen peroxide formed on the aerosol surfaces may transfer its O-isotopic signature to the water reservoir, thus producing mass independently fractionated secondary mineral evaporites. The formation of peroxide via heterogeneous chemistry on aerosol surfaces also reveals a previously undescribed oxidative process of utility in understanding ozone and oxygen chemistry, both on Mars and Earth.
机译:关于火星生命的争论围绕着ALH84001陨石中球形的微米级矿物碳酸盐的来源。因此,识别形成碳酸盐的火星过程至关重要。本文报道了一个先前未描述的碳酸盐形成过程,该过程发生在地球上以及可能在火星上。我们确定了在地面气溶胶中具有超标17O(0.4-3.9‰)的微米级碳酸盐。独特的O同位素组成从机械上描述了气溶胶表面上的大气异质化学反应。伴随的实验室实验定义了当O3与表面吸附的水反应时,臭氧同位素异常通过过氧化氢的形成而转变为碳酸盐。这种先前无法确定的化学反应场景为在SNC中发现的同位素异常碳酸盐(钙锰矿,纳赫石,变硅钙石)火星陨石和陆地大气碳酸盐提供了解释。在气溶胶表面形成的异常过氧化氢可能会将其O同位素特征转移到储水罐,从而产生质量独立的分馏次生矿物蒸发物。通过气溶胶表面上的异质化学形成过氧化物也揭示了以前未描述的氧化过程,可用于理解火星和地球上的臭氧和氧化学。

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