We look at soilchemistry—for example, how much nitrogen or magnesium there is in the soil in one spot—and we compare it with the chemistryof the soil a short distance away.
我们会观察土壤的化学性质——比如某个地方的土壤里有多少氮或者镁——然后与附近土壤的化学性质作比较。
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And NASA's two Viking landers in 1976, equipped with sophisticated life chemistry experiments, analyzed the soil and found it devoid of the organic building blocks of life.