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March 17th, 2008
Ten Questions Shaping 21st Century Earth Sciece Identified

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PR — Ten
questions driving the geological and planetary sciences were identified
today in a new report by the National Research Council.  Aimed
at reflecting the major scientific issues facing earth science at the
start of the 21st century, the questions represent where the field
stands, how it arrived at this point, and where it may be headed.

 

"With
all the advancements over the last 20 years, we can now get a better
picture of Earth by looking at it from micro- to macro-perspectives,
such as discerning individual atoms in minerals or watching continents
drift and mountains grow
," said Donald
J. DePaolo, professor of geochemistry at the University of California
at Berkeley and chair of the committee that wrote the report.  "To
keep the field moving forward, we have to look to the past and ask
deeper fundamental questions, about the origins of the Earth and life,
the structure and dynamics of planets, and the connections between life
and climate, for example."

The report was requested by the U.S. Department of Energy, National Science Foundation, U.S. Geological Survey, and NASA.  The
committee selected the question topics, without regard to
agency-specific issues, and covered a variety of spatial scales —
subatomic to planetary — and temporal scales — from the past to the
present and beyond.

 

The committee canvassed the geological community and deliberated at length to arrive at 10 questions.  Some
of the questions present challenges that scientists may not understand
for decades, if ever, while others are more tractable, and significant
progress could be made in a matter of years, the report says. 
The
committee did not prioritize the 10 questions — listed with associated
illustrative issues below — nor did it recommend specific measures for
implementing them.

 

How did Earth and other planets form?  While
scientists generally agree that this solar system’s sun and planets
came from the same nebular cloud, they do not know enough about how
Earth obtained its chemical composition to understand its evolution or
why the other planets are different from one other.  Although
credible models of planet formation now exist, further measurements of
solar system bodies and extrasolar objects could offer insight to the
origin of Earth and the solar system.

 

What happened during Earth’s "dark age" (the first 500 million years)?  Scientists
believe that another planet collided with Earth during the latter
stages of its formation, creating debris that became the moon and
causing Earth to melt down to its core. 
This
period is critical to understanding planetary evolution, especially how
the Earth developed its atmosphere and oceans, but scientists have
little information because few rocks from this age are preserved. 

 

How did life begin?  The origin of life is one of the most intriguing, difficult, and enduring questions in science.  The
only remaining evidence of where, when, and in what form life first
appeared springs from geological investigations of rocks and minerals.  To
help answer the question, scientists are also turning toward Mars,
where the sedimentary record of early planetary history predates the
oldest Earth rocks, and other star systems with planets.

 

How does Earth’s interior work, and how does it affect the surface?  Scientists know that the mantle and core are in constant convective motion.  Core
convection produces Earth’s magnetic field, which may influence surface
conditions, and mantle convection causes volcanism, seafloor
generation, and mountain building.  However,
scientists can neither precisely describe these motions, nor calculate
how they were different in the past, hindering scientific understanding
of the past and prediction of Earth’s future surface environment. 

 

Why does Earth have plate tectonics and continents?  Although
plate tectonic theory is well established, scientists wonder why Earth
has plate tectonics and how closely it is related to other aspects of
Earth, such as the abundance of water and the existence of the
continents, oceans, and life.  Moreover,
scientists still do not know when continents first formed, how they
remained preserved for billions of years, or how they are likely to
evolve in the future.  These are especially important questions as weathering of the continental crust plays a role in regulating Earth’s climate. 

 

How are Earth processes controlled by material properties?  Scientists
now recognize that macroscale behaviors, such as plate tectonics and
mantle convection, arise from the microscale properties of Earth
materials, including the smallest details of their atomic structures.  Understanding
materials at this microscale is essential to comprehending Earth’s
history and making reasonable predictions about how planetary processes
may change in the future. 

 

What causes climate to change — and how much can it change?  Earth’s
surface temperature has remained within a relatively narrow range for
most of the last 4 billion years, but how does it stay well-regulated
in the long run, even though it can change so abruptly?  Study
of Earth’s climate extremes through history — when climate was
extremely cold or hot or changed quickly — may lead to improved
climate models that could enable scientists to predict the magnitude
and consequences of climate change.

 

How has life shaped Earth — and how has Earth shaped life?  The exact ways in which geology and biology influence each other are still elusive.  Scientists
are interested in life’s role in oxygenating the atmosphere and
reshaping the surface through weathering and erosion.  They also seek to understand how geological events caused mass extinctions and influenced the course of evolution.

 

Can earthquakes, volcanic eruptions, and their consequences be predicted?  Progress
has been made in estimating the probability of future earthquakes, but
scientists may never be able to predict the exact time and place an
earthquake will strike.  Nevertheless, they
continue to decipher how fault ruptures start and stop and how much
shaking can be expected near large earthquakes.  For
volcanic eruptions, geologists are moving toward predictive
capabilities, but face the challenge of developing a clear picture of
the movement of magma, from its sources in the upper mantle, through
Earth’s crust, to the surface where it erupts.

 

How do fluid flow and transport affect the human environment?  Good
management of natural resources and the environment requires knowledge
of the behavior of fluids, both below ground and at the surface, and
scientists ultimately want to produce mathematical models that can
predict the performance of these natural systems.  Yet,
it remains difficult to determine how subsurface fluids are distributed
in heterogeneous rock and soil formations, how fast they flow, how
effectively they transport dissolved and suspended materials, and how
they are affected by chemical and thermal exchange with the host
formations. 

 

This study was sponsored by the U.S. Department of Energy, National Science Foundation, U.S. Geological Survey, and NASA.  The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies.  They
are private, nonprofit institutions that provide science, technology,
and health policy advice under a congressional charter.  The
Research Council is the principal operating agency of the National
Academy of Sciences and the National Academy of Engineering.  A committee roster follows.

Copies of Origin and Evolution of Earth:  Research Questions for a Changing Planet are available from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at http://www.nap.edu.  Reporters may obtain a copy from the Office of News and Public Information (contacts listed above). 


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