EARTH SCIENCE OVERVIEW


The Earth System

To the best of our knowledge, Earth is unique among the planets of the solar system in its abundance of water in all three phases - gas, liquid, and solid - a consequence of the Earth's radiative balance. In turn, this balance is strongly affected by global water cycles and biogeochemistry. Another unique feature of the Earth is that oxygen and reduced gases, such as methane, coexist in the atmosphere. Atmospheric composition and climate are intimately tied to biological processes like photosynthesis and decomposition. Therefore, understanding even the simplest aspects of the Earth system requires knowledge of geophysics, geochemistry, and biology.

We regard the Earth system as two subsystems - physical climate and biogeochemical cycles - linked by the global hydrologic cycle. Examination of these subsystems and their linkages defines the critical questions that the Earth Observing System (EOS) addresses.



Earth Science Enterprise Overview

There are strong scientific indications that natural change in the Earth system is being accelerated by human intervention. As a result, planet Earth faces the possibility of rapid environmental changes that would have a profound impact on all nations. However, we do not fully understand either the short-term effects of our activities, or their long-term implications - many important scientific questions remain unanswered. The National Aeronautics and Space Administration (NASA) is working with the national and international scientific communities to establish a sound scientific basis for addressing these critical issues through research efforts coordinated under the U.S. Global Change Research Program, the International Geosphere-Biosphere Program, and the World Climate Research Program. The Earth Science Enterprise is NASA's contribution to the U.S. Global Change Research Program.

NASA's Earth Science Enterprise will use space- and surface-based measurement systems to provide the scientific basis for understanding global change. The space-based components will provide a constellation of satellites to monitor the Earth from space. A major component of the Earth Science Enterprise is the Earth Observing System (EOS).


EOS Overview

Developing an understanding of how our home planet, Earth, functions in response to interactions among land, oceans, and atmosphere has presented a critical challenge that must be met if we are to predict the impacts of human activities on local, regional, and global climate change. The field of Earth science has matured from the point of understanding ocean, land, and atmosphere processes separately, to studying their connections on a global scale. The Earth Observing System will provide data which are critical to increasing our understanding of the Earth as an integrated system.

The overall objective of the EOS Program is to determine the extent, causes, and regional consequences of global climate change. EOS will provide sustained space-based observations that will allow researchers to monitor climate variables over time to determine trends. A constellation of EOS satellites will acquire global data, beginning in 1998 and extending well into the 21st century.

With scientific information from the Earth Observing System, both naturally occurring and human-induced global climate changes will be studied. Both must be understood to determine how to alter human behavior appropriately to avoid, mitigate, or adapt to human-induced climate changes that prove most detrimental to the environment. Also, the regional consequences of global climate change (such as changes in precipitation patterns, length of growing seasons, etc.) must be understood to determine which aspects of climate change are most harmful, and how to adapt to those changes that mankind cannot avoid.

In addition to a constellation of satellites, the EOS program will support a comprehensive data and information system, a community of scientists performing research, and extensive ground and airborne measurement campaigns. NASA's commitment to making Earth science data easily available is also a key component of the EOS program.