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Asteroids, Comets, Meteors, and Near-Earth Objects


Everyone learns about the handful of “major planets” in elementary school, but the Sun’s followers truly number in the thousands. Dwarf planets and minor solar system bodies, better known as asteroids and comets, circle the Sun in flocks and as loners. They range in size from dust motes to globes over five hundred miles across. The minor planets close to the Sun are metallic or stony, while those farther out are “dirty snowballs”-worlds of ice laced with stones.

There are many asteroids and comets with orbits that come closer than twenty-eight million miles (forty-five million kilometers) to the orbit of the Earth. They are called near-Earth objects (NEOs). The NEOs are worlds of opportunity and danger for mankind. One may be one of the first destinations for the Multi-Purpose Crew Vehicle. Because many asteroids are rich in mineral resources, they could be mined for materials to support space colonies and industries on Earth.

The danger lies with NEOs as well. Some NEOs could do more than approach the Earth-they could collide with it. In fact, this has happened throughout history, and we refer to the NEOs of this kind as meteoroids. Most meteoroids are about the size of sand grains. Unless they are properly protected, spacecraft can be punctured by meteoroids. Most meteoroids burn up harmlessly above our heads as meteors, also known as shooting stars. The meteoroids that survive their trip through our atmosphere, called meteorites, are usually small, even microscopic. However, it would not take much for a meteorite to cause serious damage: Barringer Crater in Arizona, which is about three-quarters of a mile wide, was made by a meteorite about a hundred and fifty feet in diameter. If another meteorite of the same size hit a city, the devastation would be similar to that caused by one of the atomic bombs dropped over Hiroshima or Nagasaki. The impacts of larger meteorites are currently thought to be a cause of mass extinctions, such as the disappearance of the dinosaurs. If you are a NASA HQ employee, please consider subscribing to our news alert on Near-Earth objects to get the latest news. If you are a member of the public, you can sign up for the JPL Asteroid Watch news through Twitter.

All items are available at the Headquarters Library, except as noted. NASA Headquarters employees and contractors: Call x0168 or email for information on borrowing or in-library use of any of these items. Members of the public: Contact your local library for the availability of these items. NASA Headquarters employees can request additional materials or research on this topic. The Library welcomes your comments or suggestions about this webpage.


Bell, Jim, and and Jacqueline Mitton. Asteroid Rendezvous: NEAR Shoemaker’s Adventures at Eros. Cambridge, UK; New York, NY: Cambridge University Press, 2002.
QB651 .A84 2002 BOOKSTACKS

Bevan, Alex, and John de Laeter. Meteorites: A Journey Through Space and Time. Washington, DC: Smithsonian Institution Press in association with the University of New South Wales Press, 2002.
QB755 .B48 2002 BOOKSTACKS

Bobrowsky, Peter T., and Hans Rickman. Comet/Asteroid Impacts and Human Society: An Interdisciplinary Approach. New York, NY: Springer, 2007.
QB721 .C645 2007 BOOKSTACKS

Committee to Review Near-Earth-Object Surveys and Hazard Mitigation Strategies, National Research Council of the National Academies. Defending Planet Earth: Near-Earth-object Surveys and Hazard Mitigation Strategies. Washington, DC: National Academies Press, 2010.
QB651 .D444 N385 2010 BOOKSTACKS
Note: This title is available online through the National Academies Press.

Farquhar, Robert Willard. Fifty Years on the Space Frontier: Halo Orbits, Comets, Asteroids, and More. Denver, CO: Outskirts Press, 2010.
QB355 .F377 F548 2010 BOOKSTACKS

McCurdy, Howard E. Low-cost Innovation in Spaceflight: The Near Earth Asteroid Rendezvous (NEAR) Shoemaker Mission. Washington, DC: National Aeronautics and Space Administration, Office of External Relations, History Division, 2005.
TL795.4 .M34 2004 BOOKSTACKS

Note: This title is available online as document no. 20050159707 through the NASA Technical Reports Server.

Schulz, Rita (ed.). Rosetta: ESA’s Mission to the Origin of the Solar System. New York, NY: Springer, 2009.
QB721 .R668 2009 BOOKSTACKS

Sommer, Geoffrey S. Astronomical Odds: A Policy Framework for the Cosmic Impact Hazard. Santa Monica, CA: RAND, 2005.
QB651 .S664 2005 BOOKSTACKS

United States. Congress. House. Committee on Science and Technology. Subcommittee on Space and Aeronautics. Near-Earth Objects (NEOS): Status of the Survey Program and Review of NASA’s 2007 Report to Congress. Washington, DC: US GPO, 2008.
KF27 .S3995 2007N BOOKSTACKS

United States. National Aeronautics and Space Administration. Near-Earth Object Survey and Deflection Analysis of Alternatives: Report to Congress. Washington, DC: National Aeronautics and Space Administration, 2007.
QB651 .N43 2007 BOOKSTACKS


American Museum of Natural History. Cosmic Collisions. New York, NY: American Museum of Natural History, 2006.
QB466 .C64 A44 2006 DVD

Yoshikama, Makato. Return of the Falcon: The story of “Hayabusa,” a Spacecraft to Explore an Asteroid. Tokyo, Japan: Japan Aerospace Exploration Agency, 2007.
QB651 .J2 R48 2007 DVD VIDEO-COLL
Note: The NASA HQ Library also has a booklet that accompanies this disk.


The e-book listed below is available to the general public through the NASA Astrophysics Data System (ADS) Virtual Library.

King, Elbert A. Chondrules and their Origins, Lunar and Planetary Institute, 1983.


NASA Websites

Chodas, Paul. Center for Near Earth Object Studies. September 20, 2017 [September 21, 2017].

Greicius, Tony. Dawn Mission. June 13, 2011 [June 17, 2011].

__________. EPOXI. June 16, 2011 [June 17, 2011].
Note: Since the success of Deep Impact’s primary mission, NASA has renamed the spacecraft and has sent it on the EPOXI mission.

Nelson, Jon. Asteroid Watch. June 16, 2011 [June 17, 2011].

Williams, David R. Asteroids. June 24, 2009 [June 17, 2011].

__________. Comets. July 25, 2008 [June 17, 2011].

Other Websites

American Meteor Society. 2012 [Feb. 6, 2012].

Barringer Crater Company. 2010 [June 17, 2011].
Note: This is the website of the family firm that owns the famous crater in Arizona.

Cometary Science Laboratory and Archive. 2010 [June 17, 2011].

Kronk, Gary. Meteor Showers Online. 2007 [June 17, 2011].
Note: Lists the major meteor showers for the year.

The Meteoritical Society. May 20, 2011 [June 17, 2011].
Note: Meteoritics is the study of meteorites, as opposed to meteorology, which studies the weather.

Minor Planet Center. May 17, 2011. [June 17, 2011].