So far, as far as we know comet Wild 2 is a unique object. Donald E. Brownlee More Quotes by Donald E. Brownlee More Quotes From Donald E. Brownlee We've undergone a very heavy level of scrutiny by review boards because of Genesis and because of the Columbia accident. . . . It was a cultural shift in NASA, that you're now required to understand all the risks. Donald E. Brownlee boards risk levels There's almost no gravity at the surface. If you were standing on [the surface], you could jump into orbit. Donald E. Brownlee orbit gravity surface