We must imagine the early Earth as a mixture of rocky materials, metals, and trapped gases, subject to constant bombardment by smaller planetesimals and without much of an atmosphere.
我们必须想象早期的地球是岩石材料、金属和封闭气的混合物，受到较小的星子的持续轰击，没有多少大气。
2
Within each orbit, collisions between planetesimals generated immense heat and energy.
在每个轨道内，天体之间的碰撞产生了巨大的热量和能量。
3
This material gradually coalesced into lumps called planetesimals as gravity and chance smashed smaller pieces together.