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Introduction

OVERVIEW OF LIVING ON A RESTLESS PLANET

The premise of the Solid-Earth Science Working Group’s (SESWG’s) Living on a Restless Planet1 is that data from National Aeronautics and Space Administration (NASA) satellites and aircraft and the advanced modeling techniques developed to interpret these data have a major role to play in detecting, quantifying, and understanding the dynamic processes affecting the solid earth and the interactions between the solid earth and its fluid envelopes. It is widely accepted that some of the most important scientific questions in earth and planetary science relate to defining and understanding these processes and that such knowledge is essential for establishing a baseline for exploration of other planets. The report emphasizes that these processes are of direct societal importance (and of value to federal, state, and local hazard-mitigation programs) since they underlie natural hazards such as earthquakes, volcanic eruptions, and landslides.

The report identifies six broad challenges that are of fundamental scientific importance, have strong implications for society, are amenable to substantial progress through new observations, and for which NASA can provide leadership by making possible critical and unique observations and analysis. These scientific challenges are:

  1. What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards?

  2. How do tectonics and climate interact to shape the earth’s surface and create natural hazards?

  3. What are the interactions among ice masses, oceans, and the solid earth and their implications for sea-level change?

  4. How do magmatic systems evolve and under what conditions do volcanoes erupt?

  5. What are the dynamics of the mantle and crust and how does the earth’s surface respond?

  6. What are the dynamics of the earth’s magnetic field and its interactions with the earth system?

Based on these scientific challenges, the SESWG report defines five primary observational strategies, each of which, if implemented, would contribute to addressing two or more of the scientific challenges listed in the preceding paragraph:

  1. surface deformation

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National Aeronautics and Space Administration, Living on a Restless Planet, Solid Earth Science Working Group Report, Pasadena, Calif., 63 pp., 2002, <http://solidearth.jpl.nasa.gov/seswg.html>.



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Review of NASA’s Solid-Earth Science Strategy 1 Introduction OVERVIEW OF LIVING ON A RESTLESS PLANET The premise of the Solid-Earth Science Working Group’s (SESWG’s) Living on a Restless Planet1 is that data from National Aeronautics and Space Administration (NASA) satellites and aircraft and the advanced modeling techniques developed to interpret these data have a major role to play in detecting, quantifying, and understanding the dynamic processes affecting the solid earth and the interactions between the solid earth and its fluid envelopes. It is widely accepted that some of the most important scientific questions in earth and planetary science relate to defining and understanding these processes and that such knowledge is essential for establishing a baseline for exploration of other planets. The report emphasizes that these processes are of direct societal importance (and of value to federal, state, and local hazard-mitigation programs) since they underlie natural hazards such as earthquakes, volcanic eruptions, and landslides. The report identifies six broad challenges that are of fundamental scientific importance, have strong implications for society, are amenable to substantial progress through new observations, and for which NASA can provide leadership by making possible critical and unique observations and analysis. These scientific challenges are: What is the nature of deformation at plate boundaries and what are the implications for earthquake hazards? How do tectonics and climate interact to shape the earth’s surface and create natural hazards? What are the interactions among ice masses, oceans, and the solid earth and their implications for sea-level change? How do magmatic systems evolve and under what conditions do volcanoes erupt? What are the dynamics of the mantle and crust and how does the earth’s surface respond? What are the dynamics of the earth’s magnetic field and its interactions with the earth system? Based on these scientific challenges, the SESWG report defines five primary observational strategies, each of which, if implemented, would contribute to addressing two or more of the scientific challenges listed in the preceding paragraph: surface deformation 1   National Aeronautics and Space Administration, Living on a Restless Planet, Solid Earth Science Working Group Report, Pasadena, Calif., 63 pp., 2002, <http://solidearth.jpl.nasa.gov/seswg.html>.

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Review of NASA’s Solid-Earth Science Strategy high-resolution topography variability of the earth’s magnetic field variability of the earth’s gravity field and imaging spectroscopy of the earth’s changing surface.2 We note that imaging spectroscopy is the most practical way to measure certain surface properties remotely—it is not a fundamental scientific measurement. For consistency with the other observational strategies, we discuss it under the title “surface properties using imaging spectroscopy.” For each of the observational strategies, the SESWG report makes specific recommendations for implementation at short-term (1–5 years), near-term (5–10 years), and long-term (10–25 years) time scales. In addition to these five observational strategies, the report makes recommendations regarding space geodetic networks and the International Terrestrial Reference Frame, as well as promising techniques and observations. In general, priorities are not assigned to the recommendations, with the important exception that the launching of a satellite dedicated to interferometric synthetic aperture radar (InSAR) measurements of the land surface is identified as the single highest priority for NASA’s solid-earth science program. The report concludes with a description of elements that complement the recommended observational strategy, including research and analysis, information systems, technology development, supporting framework, and education. ORGANIZATION OF THIS REPORT Our report covers the five observational strategies highlighted by the SESWG report and the specific recommendations related to each strategy. For each of the strategies, we provide a brief overview of its background; repeat the immediate, near-term, and long-term recommendations of the SESWG report; describe the scientific and societal benefits that would accrue from proceeding as recommended; summarize the relationship of the recommendations to national priorities in solid-earth science laid out in strategic plans of relevant federal agencies and interagency organizations (summarized and referenced in Appendix A); analyze whether the strategy as defined identifies ways in which NASA can make a unique contribution; analyze the strengths and weaknesses of the recommendations and highlight key technical challenges and advances that will be necessary to implement the strategies as described; and summarize our analysis. After analyzing the observational strategies, we conclude with a summary of our evaluation, highlighting those aspects of the recommendations in the SESWG report that are of highest priority. We note at the outset that there are aspects of the SESWG report that we have chosen not to review. For example, we do not evaluate explicitly the validity of the six broad scientific challenges that motivated the proposed observational strategies. Our reasoning is that these scientific challenges reflect classic, major issues in earth science.3 Although considerable and 2   National Aeronautics and Space Administration, Living on a Restless Planet, Solid Earth Science Working Group Report, Pasadena, Calif., p. 29, 2002, <http://solidearth.jpl.nasa.gov/seswg.html>. 3   For example, the scientific themes recommended to guide NASA’s solid-earth program a decade ago were similar in scope, although somewhat different in focus, to the SESWG scientific challenges. They

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Review of NASA’s Solid-Earth Science Strategy interesting debate may arise about any aspect of these challenges, they are manifestly so important and largely uncontroversial that we chose not to invest our limited time in such debate. Likewise, we have chosen not to comment on the descriptions of supporting infrastructure (e.g., space geodetic networks, information systems) and education, except as they relate to the five main observational strategies. Again, these issues are not controversial at the level of detail given in the SESWG report. These decisions reflected our interpretation that our charge was to focus on the major initiatives proposed in the report.     included (1) interactions of the earth’s surface and interior with the oceans and atmosphere on time scales of hours to millions of years; (2) the evolving landscape as a record of tectonics, volcanism, and climate change during the last 2 million years; (3) the motions and deformations of the lithosphere within the plates and across plate boundaries; (4) the evolution of continents and the structure of the lithosphere; (5) the dynamics of the mantle including the driving mechanisms of plate motion; and (6) the dynamics of the core and the origin of the magnetic field. See National Aeronautics and Space Administration, Solid Earth Science in the 1990s, Volume 1—Program Plan, NASA Technical Memorandum 4256, Washington, D.C., 61 pp., 1991.

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