Department of Earth and Planetary Sciences, University of California Davis, Davis, CA 95616, USA.
Science. 2022 Jul 15;377(6603):320-324. doi: 10.1126/science.abk1175. Epub 2022 Jun 16.
Volatile elements are thought to have been delivered to Solar System terrestrial planets late in their formation through accretion of chondritic meteorites. Mars can provide information on inner Solar System volatile delivery during the earliest planet formation stages. We measured krypton isotopes in the martian meteorite Chassigny, representative of the planet's interior. We found chondritic krypton isotope ratios, which imply early incorporation of chondritic volatiles. The atmosphere of Mars has different (solar-type) krypton isotope ratios, indicating that it is not a product of magma ocean outgassing or fractionation of interior volatiles. Atmospheric krypton instead originates from accretion of solar nebula gas after formation of the mantle but before nebular dissipation. Our observations contradict the common hypothesis that during planet formation, chondritic volatile delivery occurred after solar gas acquisition.
挥发性元素被认为是通过球粒陨石的吸积在太阳系类地行星形成后期输送到太阳系中的。火星可以为内太阳系挥发性物质在早期行星形成阶段的输送提供信息。我们测量了火星陨石 Chassigny 中的氪同位素，该陨石代表了行星的内部。我们发现了球粒陨石型的氪同位素比值，这意味着早期加入了球粒陨石挥发物。火星大气中的氪同位素比值不同（与太阳型相同），这表明火星大气不是岩浆海洋脱气或内部挥发分分馏的产物。相反，大气中的氪来源于地幔形成后、星云中气体消散前对太阳星云气体的吸积。我们的观测结果与行星形成过程中，球粒陨石挥发性物质输送发生在太阳气体吸收之后的常见假说相矛盾。
