They may have been a source of part of the atmosphere of the terrestrial planets, and they are believed to have been the planetesimal-like building blocks for some of the outer planets and their satellites.

• 他们本来可能是地球行星大气层的来源之一，而目前的说法一直是他们是类星子堆积块，由一些外部行星和他们的卫星所造成。