The solar wind and energetic magnetospheric ions are important agents for modification of the planetary surfaces and atmospheres with which they interact. Knowledge of the details of the sputtering mechanisms involved in these interactions can help in determining the interrelation of a number of planetary processes. In this paper I shall discuss several sites in the solar system where sputtering phenomena are significant. Our quantitative understanding of these examples could be extended if we had a more detailed picture of the sputtering of insulators. Recent experimental results that bear on these problems as well as the gaps in our knowledge that prevent further progress will be presented.