It's the particular type of material, which also included grainsofice and organic chemicals - just what you'd expect from a pulverized comet.
那是一类包含冰和机化合物的特殊物质，而这些物质只有被粉碎的彗星才能产生。
2
As each year's snow accumulation lay on the surface, evaporation and melting caused the snowflakes slowly to lose their feathery points and become tiny grainsofice.
由于每年的雪花积累在表面之上，蒸发和融化使得雪花慢慢失去其羽状尖端而变成微小的冰粒。
3
With time and pressure from above, the many small icegrains joined and changed to larger crystals, and eventually the deeper crystals merged into a solid mass ofice.