This artwork was made as a study in Volumetric lighting and procedural model generation. I took a single Icosphere, applied several levels of subdivision, and then used world space Voronoi textures to generate the meteor impact points. I then made a moderately advanced material utilizing translucency, diffuse, fresnel, and other techniques to give them a more cartoony, friendly look.
Once I had a good result, I then duplicated and scaled it several times (world space textures ensured all of them were different) and then made a particle system from the group. The rest is camera position and color grading.