Prologue

I doubt that any Earth-born space farer could ever tire of looking at our home planet from space. It is a beautiful, wondrously diverse sphere that routinely enthralls space crews. Because the number of people living and working in space, for increasingly diverse reasons, is likely to grow rapidly over the next 25 years, the possibility now exists for observations from this unique vantage point to become an element of first-hand "field experience" for many Earth scientists.

Given this potential, it is instructive to compare our approach to learning about the Earth with our approach to other bodies in the solar system. Over many years, our knowledge of our neighboring planets has advanced from the very coarse telescopic views of colored planetary discs to the more detailed views provided by imaging spacecraft. In only one case have we extended our resolution to the mesoscopic and microscopic scales of observation with which we routinely view terrestrial geologic phenomena. In contrast, our understanding of the Earth begins on small personal scales (often childhood rock collections) and only becomes global, in any sense of the word, through years of indoctrination and intellectual synthesis. Now, after 27 years of development, we have the means to venture sufficiently far from our home planet to view it -with both human and electronic eyes- as a single entity, as we first see our neighboring planets. We are just beginning to glean the lessons that this new perspective contains, but it is certain that they will be of tremendous significance to all mankind, in both practical and intellectual terms.

For example, what benefit will this new view bring to our own scientific discipline? The history of geology is full of cases in which access to a new region for direct observations was a vital factor in the formulation of new ideas and the advent of new models. It is exciting to consider what the effect might be on the foundations of current geological thinking if many of us were as directly familiar with the orbital view of our home planet as we are today with our individual field areas.

Nicholas M. Short and his colleagues have assembled an impressive collection of images and detailed supporting data that help us to begin to understand this entity called Earth in a planetary context. This book should be a vital reference for all who find this a stimulating new perspective and especially for those who hope someday to view it with their own eyes.