Sossi Paolo A, Stotz Ingo L, Jacobson Seth A, Morbidelli Alessandro, O'Neill Hugh St C
Institute of Geochemistry and Petrology, ETH Zürich, CH-8092, Zürich, Switzerland.
Institut für Geophysik, Ludwig-Maximilians Universität Münich, Münich, Germany.
Nat Astron. 2022 Jul 7;6(8):951-960. doi: 10.1038/s41550-022-01702-2.
Chondritic meteorites are thought to be representative of the material that formed the Earth. However, the Earth is depleted in volatile elements in a manner unlike that in any chondrite, and yet these elements retain chondritic isotope ratios. Here we use N-body simulations to show that the Earth did not form from chondrites, but rather by stochastic accretion of many precursor bodies whose variable compositions reflect the temperatures at which they formed. Earth's composition is reproduced when initial temperatures of planetesimal- to embryo-sized bodies are set by disk accretion rates of (1.08±0.17)×10 solar masses/yr, although they may be perturbed by Al heating on bodies formed at different times. Our model implies that a heliocentric gradient in composition was present in the protoplanetary disc and that planetesimals formed rapidly within ~1 Myr, in accord with radiometric volatile depletion ages of the Earth.
球粒陨石被认为是形成地球的物质的代表。然而，地球在挥发性元素方面以一种不同于任何球粒陨石的方式出现亏损，而这些元素却保留着球粒陨石的同位素比率。在这里，我们使用N体模拟来表明，地球并非由球粒陨石形成，而是由许多前身天体的随机吸积形成，这些天体的可变成分反映了它们形成时的温度。当行星胚胎大小天体的初始温度由盘吸积率（1.08±0.17）×10太阳质量/年设定时，地球的成分就能被重现，尽管它们可能会受到不同时期形成的天体上铝加热的干扰。我们的模型表明，原行星盘中存在着以太阳为中心的成分梯度，并且行星胚胎在约100万年的时间内迅速形成，这与地球放射性挥发性元素亏损年龄一致。
