星云盘在演化成尘层的过程中,因尘粒沉降速率的不同,使液滴状铁镍物质首先到达并集中于星云盘赤道面,成为中心层,球粒陨石物质分布于中心层上下。中心层的铁镍星子首先形成液态行星核,然后吸积上下层的球粒陨石星子形成固态行星幔,并造成行星幔的横向不均匀。 As the nebula disk evolves into a dust layer, the droplet-like nickel-iron material first arrives and concentrates in the equatorial plane of the nebula disk due to the different sedimentation rates of the dust particles, becoming the central layer. The chondrite material is distributed above and below the central layer. The core of the iron-nickel asteroids first form a liquid planet core, and then accretion of the upper and lower chondrite stars form solid-state mantle, and cause the mantle of the lateral uneven.