The oxygen‐isotopic composition of Earth and Mars

Abstract— The small difference between the O‐isotopic mass fractionation lines of the Earth and Mars has been measured precisely using a laser fluorination system. The precision achieved from the two sample sets is better than ±0.014‰, with the offset (Δ 17 O) between Mars and Earth measured as +0.321‰. This result shows that all the Shergotty—Nakhla—Chassigny (SNC) meteorites define a high level of isotopic homogeneity, comparable to that of crustal material on the Earth, indicating that these meteorites originate, unequivocally, from a single, common parent body (Mars). Allan Hills 84001, with its ancient age (4.56 Ga), shows that any initial heterogeneity imparted into Mars from the nebula was homogenised very early in the formation history of the planet.