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Report Examines Options for Detecting and Countering Near-Earth Objects

WASHINGTON -- A new report from the National Research Council lays out options NASA could follow to detect more near-Earth objects (NEOs) – asteroids and comets that could pose a hazard if they cross Earth's orbit. The report says the $4 million the U.S. spends annually to search for NEOs is insufficient to meet a congressionally mandated requirement to detect NEOs that could threaten Earth.

Date: Jan. 23, 2010
Contacts: Sara Frueh, Media Relations Officer
Alison Burnette, Media Relations Assistant
National Research Council
202-334-2138; e-mail news@nas.edu

Congress mandated in 2005 that NASA discover 90 percent of NEOs whose diameter is 140 meters or greater by 2020, and asked the National Research Council in 2008 to form a committee to determine the optimum approach to doing so.  In an interim report released last year, the committee concluded that it was impossible for NASA to meet that goal, since Congress has not appropriated new funds for the survey nor has the administration asked for them. 

 

In its final report, the committee lays out two approaches that would allow NASA to complete its goal soon after the 2020 deadline; the approach chosen would depend on the priority policymakers attach to spotting NEOs.  If finishing NASA's survey as close as possible to the original 2020 deadline is considered most important, a mission using a space-based telescope conducted in concert with observations from a suitable ground-based telescope is the best approach, the report says.  If conserving costs is deemed most important, the use of a ground-based telescope only is preferable. 

 

The report also recommends that NASA monitor for smaller objects – those down to 30 to 50 meters in diameter -- which recent research suggests can be highly destructive.  However, the report stresses that searching for smaller objects should not interfere with first fulfilling the mandate from Congress.  Beyond completion of that mandate, the report notes the need for constant vigilance in monitoring the skies, so as to detect all dangerous NEOs.  In addition, the nation should undertake a peer-reviewed research program to better investigate the many unknown aspects connected with detecting NEOs and countering those that could be a threat.  The U.S. should also take the lead in organizing an international entity to develop a detailed plan for dealing with hazards from these objects.

 

In addition, the report recommends that immediate action be taken to ensure the continued operation of the Arecibo Observatory in Puerto Rico.  NASA and NSF should support a vigorous program of NEO observations at Arecibo, and NASA should also support such a program at the Goldstone Deep Space Communications Complex.  Although these facilities cannot discover NEOs, they play an important role in accurately determining the orbits and characterizing the properties of NEOs within radar range.

 

The Scope of the Hazard

 

Near-Earth objects are asteroids and comets that orbit the sun and approach or cross Earth's orbit.  An asteroid or comet about 10 kilometers in diameter struck the Yucatan peninsula 65 million years ago and caused global devastation, probably wiping out large numbers of plant and animal species including the dinosaurs.  Objects as large as this one strike Earth only about once every 100 million years on average, the report notes.  NASA has been highly successful at detecting and tracking objects 1 kilometer in diameter or larger, and continues to search for these large objects. Objects down to sizes of about 140 meters in diameter -- which NASA has been mandated to survey for -- would cause regional damage; such impacts happen on average every 30,000 years, the report says.

 

While impacts by large NEOs are rare, a single impact could inflict extreme damage, raising the classic problem of how to confront a possibility that is both very rare and very important.  Far more likely are those impacts that cause only moderate damage and few fatalities.  Conducting surveys for NEOs and detailed studies of ways to mitigate collisions is best viewed as a form of insurance, the report says.  How much to spend on these insurance premiums is a decision that must be made by the nation's policymakers.

 

Mitigating Damage

 

The report also examines what is known about methods to defend against NEOs.  These methods are new and still immature.  No single approach is effective for the full range of near-Earth objects, the committee concluded.  But with sufficient warning, a suite of four types of mitigation is adequate to meet the threat from all NEOs, except the most energetic ones. 

·              Civil defense (evacuation, sheltering in place, providing emergency infrastructure) is a cost-effective mitigation measure for saving lives from the smallest NEO impact events and is a necessary part of mitigation for larger events.

·              "Slow push" or "slow pull" methods use a spacecraft to exert force on the target object to gradually change its orbit to avoid collision with the Earth.  This technique is practical only for small NEOs (tens of meters to roughly 100 meters in diameter) or possibly for medium-sized objects (hundreds of meters), but would likely require decades of warning.  Of the slow push/pull techniques, the gravity tractor appears to be by far the closest to technological readiness.

·              Kinetic methods, which fly a spacecraft into the NEO to change its orbit, could defend against moderately sized objects (many hundreds of meters to 1 kilometer in diameter), but also may require decades of warning time. 

·              Nuclear explosions are the only current, practical means for dealing with large NEOs (diameters greater than 1 kilometer) or as a backup for smaller ones if other methods were to fail.   

 

Although all of these methods are conceptually valid, none is now ready to implement on short notice, the report says.  Civil defense and kinetic impactors are probably the closest to readiness, but even these require additional study prior to reliance on them. 

 

Given the significant unknowns about many aspects of the threat and its mitigation, the report recommends that the U.S. start a peer-reviewed, targeted research program on the hazards posed by NEOs, and how to deal with them.  Because this is a policy-driven, applied research program, it should not be in competition with basic scientific research programs or be funded from them, the report adds.   

 

The study was sponsored by NASA at the request of Congress.  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 Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies 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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[This news release and report are available at http://national-academies.org]

 

NATIONAL RESEARCH COUNCIL

Division on Engineering and Physical Sciences

Aeronautics and Space Engineering Board

Space Studies Board

 

Committee to Review Near-Earth Object Surveys and Hazard Mitigation Strategies

 

Steering Committee

 

Irwin I. Shapiro1 (chair)

Timken University Professor

Harvard University; and

Senior Smithsonian Scientist

Harvard-Smithsonian Center for Astrophysics

Cambridge, Mass.

 

Michael A'Hearn (vice chair)

Professor

Department of Astronomy

University of Maryland

College Park

 

Faith Vilas (vice chair)

Director

MMT Observatory

Mt. Hopkins, Ariz.

 

Andrew F. Cheng

Chief Scientist

Space Department

Applied Physics Laboratory

Johns Hopkins University

Laurel, Md.

 

Frank Culbertson Jr.

Senior Vice President

Orbital Sciences Corp.

Dulles, Va.

 

David C. Jewitt1

Professor

Department of Earth and Space Sciences, and

Institute for Geophysics and Planetary Physics

University of California

Los Angeles

 

Stephen Mackwell

Director

Lunar and Planetary Institute

Houston

 

H. Jay Melosh1

University Distinguished Professor

Purdue University

West Lafayette, Ind.

 

Joseph H. Rothenberg

President

Universal Space Network

Darnestown, Md.

 

Survey/Detection Panel

 

Faith Vilas (chair)

Director

MMT Observatory

Mt. Hopkins, Ariz.

 

Paul Abell

Research Scientist

Planetary Science Institute

Houston

 

Robert F. Arentz

New Business Manager

Ball Aerospace and Technologies Corp.

Boulder, Colo.

 

Lance A.M. Benner

Research Scientist

Jet Propulsion Laboratory

Pasadena, Calif.

 

William F. Bottke

Assistant Director

Department of Space Studies

Southwest Research Institute

Boulder, Colo.

 

William E. Burrows

Independent Aerospace Writer and Historian

Stamford, Conn.

 

Andrew F. Cheng

Chief Scientist

Space Department

Applied Physics Laboratory

Johns Hopkins University

Laurel, Md.

 

Robert D. Culp

Professor

Department of Aerospace Engineering Sciences

University of Colorado

Boulder

 

Yanga Fernandez

Assistant Professor of Planetary Science/Astronomy

Department of Physics

University of Central Florida

Orlando

 

Lynne Jones

LLST Fellow

Department of Astronomy

University of Washington

Seattle

 

Stephen Mackwell

Director

Lunar and Planetary Institute

Houston

 

Amy Mainzer

Research Scientist

Jet Propulsion Laboratory

Pasadena, Calif.

 

Gordon H. Pettengill1

Professor of Planetary Physics

Department of Earth, Atmospheric, and Planetary Sciences

Massachusetts Institute of Technology

Cambridge

 

John Rice

Professor

Department of Statistics

University of California

Berkeley

 

Mitigation Panel

 

Michael A'Hearn (chair)

Professor

Department of Astronomy

University of Maryland

College Park

 

Michael J.S. Beltom

President and Deputy Principal Investigator

Belton Space Exploration Initiatives LLC

Tucson, Ariz.

 

Mark Boslough

Principal Member

Exploratory Simulation Technologies Department

Sandia National Laboratories

Albuquerque, N.M.

 

Clark R. Chapman

Senior Scientist

Department of Space Studies

Southwest Research Institute

Boulder, Colo.

 

Sigrid Close

Assistant Professor

Department of Aeronautics and Astronautics

Stanford University

Stanford, Calif.

 

James A. Dator

Director

Hawaii Research Center for Future Studies

Department of Political Sciences

University of Hawaii

Manoa

 

David S.P. Dearborn

Research Scientist

Lawrence Livermore National Laboratory

Livermore, Calif.

 

Keith A. Holsapple

Professor

Aeronautics and Astronautics Department

University of Washington

Seattle

 

David Y. Kusnierkiewicz

Chief Engineer

Space Department

Applied Physics Laboratory

Johns Hopkins University

McLean, Va.

 

Paulo Lozano

Charles Stark Draper Assistant Professor
of Aeronautics and Astronautics

Department of Aeronautics and Astronautics

Massachusetts Institute of Technology

Cambridge

 

Edward D. McCullough

Principal Scientist 

Boeing (retired)

Riverside, Calif.

 

H. Jay Melosh1

University Distinguished Professor

Purdue University

West Lafayette, Ind.

 

David J. Nash2

President

Dave Nash & Associates LLC

Birmingham, Ala.

 

Daniel J. Scheeres

Professor

Department of Aerospace Engineering Sciences

Colorado Center for Astrodynamics Research

University of Colorado

Boulder

 

Sarah T. Stewart-Mukhopadhyay

John L. Loeb Associate Professor of the
Natural Sciences

Department of Earth and Planetary Sciences

Harvard University

Cambridge

 

Kathryn C. Thornton

Associate Dean

Department of Science, Technology, and
Society

University of Virginia

Charlottesville

 

RESEARCH COUNCIL STAFF

 

Dwayne A. Day

Study Co-Director

 

Paul Jackson

Study Co-Director

 

                                                                       

1 Member, National Academy of Sciences

2 Member, National Academy of Engineering