To the best of our knowledge, Earth is the only planet in the Solar System that supports life (although organic molecules may exist on one or more satellites of Jupiter and Saturn, and perhaps once on Mars; see Section 19). Life, in all its myriad forms, virtually covers the Earth. No matter where it is looked for, it has been found. Much of our planet's geophysical and biological phenomena take place in a thin shell of fluid (the atmosphere and oceans) that is about as thin in proportion to the Earth as a sheet of paper wrapped around a basketball; most other relevant activities are confined to the global land surface and an even thinner zone made up of the uppermost layers of soil and rock. And yet, the complex interactions between the biosphere and the geosphere all take place within that thin shell. Just about everything that concerns us as living beings is dependent upon the integrity of those shells of land, sea, and air.

The shells are the result of eons of dynamic processes that actually began even as the Earth itself was being formed. These processes together constitute global change. Without global change, neither we humans nor much of the rest of the biosphere would exist on the Earth, for global change has brought with it the generation of an oxygen-containing atmosphere, the existence of our protective stratospheric ozone layer, and global temperatures that are high enough (due to the greenhouse effect) to support life as we know it. Until the last few thousand years, global change has been dominantly a "natural" process.

Recent observations have led scientists to conclude that human activity is making its own contributions to global change, that our industrial and land-management practices are increasing the rate of change of several geophysical phenomena, and that some changes may even be deleterious to the biosphere. Nations around the world have banded together in a wide range of scientific and policy-based activities to determine the nature of human contributions to global change and to determine the effect such changes can have on our lives. These are gathered under the "umbrella" known as the International Geosphere-Biosphere Program (IGBP) which is, in essence, a massive effort to understand and learn to manage the world's environments.

As one of several U.S. government agencies involved in the U.S. Global Change Research Program, NASA has instituted the Mission to Planet Earth (MTPE) (more information over the Net at MTPE), based on the space-based constellation of satellites and sensors known as the Earth Observing System (EOS). This Section deals with some of the observations obtained in recent years that have led to the formation of MTPE/EOS, why MTPE/EOS was established, what it is designed to accomplish, how those goals are being approached, and what can be done with the data. 

---

[an error occurred while processing this directive] [an error occurred while processing this directive]