On Earth, measurements of the ratios of stable carbon isotopes have provided much information about geological and biological processes. For example, fractionation of carbon occurs in biotic processes and the retention of a distinctive 2-4% contrast in 13C/12C between organic carbon and carbonates in rocks as old as 3.8 billion years constitutes some of the firmest evidence for the antiquity of life on the Earth. We have developed a prototype tunable diode Laser spectrometer which demonstrates the feasibility of making accurate in situ isotopic ratio measurements on Mars. This miniaturized instrument, with an optical path length of 10 cm, should be capable of making accurate 13C/12C and 15N/14N measurements. Gas samples for measurement are to be produced by pyrolysis using soil samples as small as 50 mg. Measurements of 13C/12C, 18O/16O and 15N/14N have been made to a precision of better than 0.1% and various other isotopes are feasible. This laser technique, which relies on the extremely narrow emission linewidth of tunable diode lasers (<0.001 cm(-1)) has favorable features in comparison to mass spectrometry, the standard method of accurate isotopic ratio measurement. The miniature instrument could be ready to deploy on the 2003 or other Mars lander missions.

中文翻译：

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用于火星探测的稳定同位素激光光谱仪

在地球上，稳定碳同位素比率的测量提供了许多有关地质和生物过程的信息。例如，碳的分馏发生在生物过程中，并且在 38 亿年前的岩石中，有机碳和碳酸盐在 13C/12C 中保持了 2-4% 的独特对比，这构成了地球上生命古老的最有力证据。地球。我们开发了原型可调谐二极管激光光谱仪，它证明了在火星上进行准确的原位同位素比测量的可行性。这种微型仪器的光路长度为 10 厘米，应该能够进行准确的 13C/12C 和 15N/14N 测量。用于测量的气体样品将使用小至 50 mg 的土壤样品通过热解产生。13C/12C的测量，18O/16O 和 15N/14N 的精度优于 0.1%，其他各种同位素也是可行的。这种激光技术依赖于可调谐二极管激光器 (<0.001 cm(-1)) 的极窄发射线宽，与质谱相比，质谱是准确同位素比测量的标准方法，具有有利的特征。这种微型仪器可以准备部署在 2003 年或其他火星着陆器任务中。