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.