the body. Depending on how the body disrupts, the effect on Earth could, in some circumstances, be worse overall than if disruption were not attempted. Alternatively, disruption might lead to less total damage to Earth but more damage to, for example, a particular populated location. With the uncertainty in the present understanding of fragmentation and disruption, the committee does not now endorse disruption as a mitigation strategy, but it suggests that further study of this issue should be an important part of any research program into mitigation of the NEO hazard. (See Chapter 6.)


Finding: The mitigation of the threat from NEOs would benefit dramatically from their in situ characterization prior to mitigation if there is time.


Finding: Changing the orbit of an NEO given the current level of understanding is sufficiently uncertain that, in most cases, it requires an accompanying verification. This is easy to implement with many slow-push techniques, but it would require considerable additional effort for other techniques.


Recommendation: If Congress chooses to fund mitigation research at an appropriately high level, the first priority for a space mission in the mitigation area is an experimental test of a kinetic impactor along with a characterization, monitoring, and verification system, such as the Don Quijote mission that was previously considered, but not funded, by the European Space Agency. This mission would produce the most significant advances in understanding and provide an ideal chance for international collaboration in a realistic mitigation scenario.

BIBLIOGRAPHY

Abe, S., T. Mukai, N. Hirata, O.S. Barnouin-Jha, A.F. Cheng, H. Demura, R.W. Gaskell, T. Hashimoto, K. Hiraoka, T. Honda, T. Kubota, M. Matsuoka, T. Mizuno, R. Nakamura, D.J. Scheeres, and M. Yoshikawa. 2006. Mass and local topography measurements of Itokawa. Science 312:1344-1347.

Ahrens, T.J., and A.W. Harris. 1992. Deflection and fragmentation of near-Earth asteroids. Nature 360(6403):429-433.

Ahrens, T.J., and A.W. Harris. 1994. Deflection and fragmentation of near-Earth asteroids. In Hazards Due to Comets and Asteroids (T. Gehrels, ed.). University of Arizona Press, Tucson.

Bedrossian, P.J. 2004. Neutrons and Granite: Transport and Activation. UCRL-TR-203529. Lawrence Livermore National Laboratory, Livermore, Calif.

Britt, D.T., D. Yeomans, K. Housen, and G. Consolmagno. 2002. Asteroid density, porosity, and structure. In Asteroids III. University of Arizona Press, Tucson.

Chesley, S.R., and T.B. Spahr. 2004. Earth-impactors: Orbital characteristics and warning times. Pp. 22-37 in Mitigation of Hazardous Comets and Asteroids (M.J.S. Belton, T.H. Morgan, N.H. Samarashinha, and D.K. Yeomans, eds.). Cambridge University Press, Cambridge, Mass.

Dearborn, D.S. 2004. 21st century steam for asteroid mitigation. Planetary Defense Conference: Protecting Earth from Asteroids, Orange County, Calif. AIAA-2004-1413. American Institute of Aeronautics and Astronautics, Reston, Va.

DOE (Department of Energy). 2000. United States Nuclear Tests; July 1945 through September 1992. Report DOE/NV-209-REV 15. Department of Energy, Nevada Operations Office, Las Vegas, Nev. December. Available at http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf.

Fahnestock, E.G., and S.B. Broschart. 2009. Dynamical characterization, control, and performance analysis of gravity tractor operation at binary asteroids. First International Academy of Astronautics (IAA) Planetary Defense Conference: Protecting Earth from Asteroids, Granada, Spain, April 27-30, 2009.

Fahnestock, E.G., and D.J. Scheeres. 2008. Dynamical characterization and stabilization of large gravity tractor designs. AIAA Journal of Guidance, Control, and Dynamics 31(3):501-521.

Giorgini, J.D., L.A.M. Benner, S.J. Ostro, M.C. Nolan, and M.W. Busch. 2008. Predicting the Earth encounters of (99942) Apophis. Icarus 193(1):1-19.

Holsapple, K.A. 2002. The deflection of menacing rubble pile asteroids. Extended Abstracts Volume of the Workshop on Scientific Requirements for Mitigation of Hazardous Comets and Asteroids, Arlington, Virginia, on September 3-6, 2002. National Optical Astronomy Observatory, Tucson, Ariz. Available at http://www.noao.edu/meetings/mitigation/media/arlington.extended.pdf.

Holsapple, K.A. 2004. An assessment of our present ability to deflect asteroids and comets. Planetary Defense Conference: Protecting Earth from Asteroids, Orange County, Calif. AIAA-2004-1413. American Institute of Aeronautics and Astronautics, Reston, Va.

Holsapple, K.A. 2009. On the “strength” of the small bodies of the solar system: A review of strength theories and their implementation for analyses of impact disruptions. Planetary and Space Science 57(2):127-141.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement