Asteroid-impact avoidance

Asteroid-impact avoidance
Artist's impression of a major impact event. The collision between Earth and an asteroid a few kilometres in diameter releases as much energy as the simultaneous detonation of several million nuclear bombs.

Asteroid mitigation strategies are "planetary defense" methods by which near-Earth objects could be diverted, preventing potentially catastrophic impact events. A sufficiently large impact would cause massive tsunamis or (by placing large quantities of dust into the stratosphere, blocking sunlight) an impact winter, or both. A collision between the Earth and a ~10 km object 65 million years ago is believed to have produced the Chicxulub Crater and the Cretaceous–Tertiary extinction event.

While the chances of such an event are no greater now than at any other time in history, there is a very high chance that one will happen eventually, and recent astronomical events (such as Shoemaker-Levy 9) have drawn attention to such a threat, and advances in technology have opened up new options to prevent them.


Deflection efforts

Almost any deflection effort requires years of warning, allowing time to build a slow-pusher or explosive device to deflect the object.

An impact by a 10 km asteroid on the Earth is widely viewed as an extinction-level event, likely to cause catastrophic damage to the biosphere. Depending on speed, objects as small as 100 m in diameter are historically extremely destructive. There is also the threat from comets coming into the inner Solar System. The impact speed of a long-period comet would likely be several times greater than that of a near-Earth asteroid, making its impact much more destructive; in addition, the warning time is unlikely to be more than a few months.[1]

Finding out the material composition of the object is also necessary before deciding which strategy is appropriate. Missions like the 2005 Deep Impact probe have provided valuable information on what to expect.

History of government mandates

In a 1992 report to NASA,[2] a coordinated Spaceguard Survey was recommended to discover, verify and provide follow-up observations for Earth-crossing asteroids. This survey was expected to discover 90% of these objects larger than one kilometer within 25 years. Three years later, another NASA report[3] recommended search surveys that would discover 60-70% of short-period, near-Earth objects larger than one kilometer within ten years and obtain 90% completeness within five more years.

In 1998, NASA formally embraced the goal of finding and cataloging, by 2008, 90% of all near-Earth objects (NEOs) with diameters of 1 km or larger than could represent a collision risk to Earth. The 1 km diameter metric was chosen after considerable study indicated that an impact of an object smaller than 1 km could cause significant local or regional damage but is unlikely to cause a worldwide catastrophe.[2] The impact of an object much larger than 1 km diameter could well result in worldwide damage up to, and potentially including, extinction of the human species. The NASA commitment has resulted in the funding of a number of NEO search efforts that are making considerable progress toward the 90% goal by 2008.[dated info]

NASA is close to achieving this goal, and should achieve it within a few years. However, as the 2009 discovery of an NEO approximately 2 to 3 kilometers in diameter demonstrates, there are still large objects to be detected.

U.S. Representative George E. Brown, Jr. (D-CA) was quoted as voicing his support for planetary defense projects in Air & Space Power Chronicles, saying "If some day in the future we discover well in advance that an asteroid that is big enough to cause a mass extinction is going to hit the Earth, and then we alter the course of that asteroid so that it does not hit us, it will be one of the most important accomplishments in all of human history."

Because of Congressman Brown's long-standing commitment to planetary defense, a U.S. House of Representatives' bill, H.R. 1022, was named in his honor: The George E. Brown, Jr. Near-Earth Object Survey Act. This bill "to provide for a Near-Earth Object Survey program to detect, track, catalogue, and characterize certain near-Earth asteroids and comets" was introduced in March 2005 by Rep. Dana Rohrabacher (R-CA).[4] It was eventually rolled into S.1281, the NASA Authorization Act of 2005, passed by Congress on December 22, 2005, subsequently signed by the President, and stating in part:

The U.S. Congress has declared that the general welfare and security of the United States require that the unique competence of NASA be directed to detecting, tracking, cataloguing, and characterizing near-Earth asteroids and comets in order to provide warning and mitigation of the potential hazard of such near-Earth objects to the Earth. The NASA Administrator shall plan, develop, and implement a Near-Earth Object Survey program to detect, track, catalogue, and characterize the physical characteristics of near- Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such near-Earth objects to the Earth. It shall be the goal of the Survey program to achieve 90% completion of its near-Earth object catalogue (based on statistically predicted populations of near-Earth objects) within 15 years after the date of enactment of this Act. The NASA Administrator shall transmit to Congress not later than 1 year after the date of enactment of this Act an initial report that provides the following: (A) An analysis of possible alternatives that NASA may employ to carry out the Survey program, including ground-based and space-based alternatives with technical descriptions. (B) A recommended option and proposed budget to carry out the Survey program pursuant to the recommended option. (C) Analysis of possible alternatives that NASA could employ to divert an object on a likely collision course with Earth. The result of this directive was a report presented to Congress in early March 2007. This was an Analysis of Alternatives (AoA) study led by NASA's Program Analysis and Evaluation (PA&E) office with support from outside consultants, the Aerospace Corporation, NASA Langley Research Center (LaRC), and SAIC (amongst others).

Ongoing projects

Number of NEOs detected by various projects.

Astronomers have been conducting surveys to locate the NEOs, many (as of early 2007) funded by NASA's Near Earth Object (NEO) program office as part of their Spaceguard program. One of the best-known is LINEAR that began in 1996. By 2004 LINEAR was discovering tens of thousands of objects each year and accounting for 65% of all new asteroid detections.[5] LINEAR uses two one-meter telescopes and one half-meter telescope based in New Mexico.[6]

Spacewatch, which uses a 90 centimeter telescope sited at the Kitt Peak Observatory in Arizona, updated with automatic pointing, imaging, and analysis equipment to search the skies for intruders, was set up in 1980 by Tom Gehrels and Dr. Robert S. McMillan of the Lunar and Planetary Laboratory of the University of Arizona in Tucson, and is now being operated by Dr. McMillan. The Spacewatch project has acquired a 1.8 meter telescope, also at Kitt Peak, to hunt for NEOs, and has provided the old 90 centimeter telescope with an improved electronic imaging system with much greater resolution, improving its search capability.[7]

Other near-Earth object tracking programs include Near-Earth Asteroid Tracking (NEAT), Lowell Observatory Near-Earth-Object Search (LONEOS), Catalina Sky Survey, Campo Imperatore Near-Earth Objects Survey (CINEOS), Japanese Spaceguard Association, and Asiago-DLR Asteroid Survey.[8] Pan-STARRS completed telescope construction in 2010, and it is now actively observing.

"Spaceguard" is the name for these loosely affiliated programs, some of which receive NASA funding to meet a U.S. Congressional requirement to detect 90% of near-Earth asteroids over 1 km diameter by 2008.[9] A 2003 NASA study of a follow-on program suggests spending US$250–450 million to detect 90% of all near-Earth asteroids 140 meters and larger by 2028.[10]

Orbit@home provides distributed computing resources to optimize search strategy, and NEODyS is an online database of known NEOs.

Detection from space

On November 8, 2007, the House Committee on Science and Technology's Subcommittee on Space and Aeronautics held a hearing to examine the status of NASA's Near-Earth Object survey program. The prospect of using the Wide-field Infrared Survey Explorer was proposed by NASA officials.[11]

WISE surveyed the sky in the infrared band at a very high sensitivity. Asteroids that absorb solar radiation can be observed through the infrared band. It was used to detect NEOs, in addition to performing its science goals. It is projected that WISE could detect 400 NEOs (roughly two percent of the estimated NEO population of interest) within the one-year mission.

NEOSSat is a micro satellite by Canada's CSA that will hunt for NEOs from space.


Research published in the March 26, 2009 issue of the journal Nature, describes how scientists were able to identify an asteroid in space before it entered Earth’s atmosphere, enabling computers to determine its area of origin in the Solar System as well as predict the arrival time and location on Earth of its shattered surviving parts. The four-meter-diameter asteroid, called 2008 TC3, was initially sighted by the automated Catalina Sky Survey telescope, on October 6, 2008. Computations correctly predicted impact would occur 19 hours after discovery in the Nubian Desert of northern Sudan.[12]

A number of potential threats have been identified, such as 99942 Apophis (previously known by its provisional designation 2004 MN4), which had been given an impact probability of ~3% for the year 2029. This probability has been revised to zero on the basis of new observations.[13]

Impact probability calculation pattern

Why asteroid impact probability goes up, then down.

The ellipses in the diagram at right show the likely asteroid position at closest Earth approach. At first, with only a few asteroid observations, the error ellipse is very large and includes the Earth. Further observations shrink the error ellipse, but it still includes the Earth. This raises the impact probability, since the Earth now covers a larger fraction of the error region. Finally, yet more observations (often radar observations, or discovery of a previous sighting of the same asteroid on archival images) shrink the ellipse until the Earth is outside the error region, and the impact probability returns to near zero.[14]

Collision avoidance strategies

Various collision avoidance techniques have different trade-offs with respect to metrics such as overall performance, cost, operations, and technology readiness. There are various methods for changing the course of an asteroid/comet. These can be differentiated by various types of attributes such as the type of mitigation (deflection or fragmentation), energy source (kinetic, electromagnetic, gravitational, solar/thermal, or nuclear), and approach strategy (interception, rendezvous, or remote station). Strategies fall into two basic sets: destruction and delay.[citation needed]

Destruction concentrates on rendering the impactor harmless by fragmenting it and scattering the fragments so that they miss the Earth or burn up in the atmosphere. This does not always solve the problem, as sufficient amounts of material hitting the Earth at high speed can be devastating even if they are not collected together in a single body. The amount of energy released by a single large collision or many small collisions is essentially the same, given the physics of kinetic and potential energy. If a large amount of energy is transmitted, it could heat the surface of the planet to an uninhabitable temperature.[citation needed]

Collision avoidance strategies can also be seen as either direct, or indirect. The direct methods, such as nuclear bombs or kinetic impactors, violently intercept the bolide's path. Direct methods are preferred because they are generally less costly in time and money. Their effects may be immediate, thus saving precious time. These methods might work for short-notice, or even long-notice threats, from solid objects that can be directly pushed, but probably not effective against loosely aggregated rubble piles. The indirect methods, such as gravity tractors, attaching rockets or mass drivers, laser cannon, etc., will travel to the object then take more time to change course up to 180 degrees to fly alongside, and then will also take much more time to change the asteroid's path just enough so it will miss Earth.

Many NEOs are "flying rubble piles" only loosely held together by gravity, and a deflection attempt might just break up the object without sufficiently adjusting its course. If an asteroid breaks into fragments, any fragment larger than 35 m across would not burn up in the atmosphere and itself could impact Earth. Tracking the thousands of fragments that could result from such an explosion would be a very daunting task. Many small impacts could cause greater devastation than one large impact.

Against some rubble piles, a nuclear bomb may be delivered to it and dock with it, then it could penetrate to its center, and explode sending fragments in all directions, thus reducing the amount of material reaching the Earth. The explosion can also increase the surface area of the threat enough so that more pieces will burn up harmlessly high in the atmosphere.[citation needed]

Delay exploits the fact that both the Earth and the impactor are in orbit. An impact occurs when both reach the same point in space at the same time, or more correctly when some point on Earth's surface intersects the impactor's orbit when the impactor arrives. Since the Earth is approximately 12,750 km in diameter and moves at approx. 30 km per second in its orbit, it travels a distance of one planetary diameter in about 425 seconds, or slightly over seven minutes. Delaying, or advancing the impactor's arrival by times of this magnitude can, depending on the exact geometry of the impact, cause it to miss the Earth. By the same token, the arrival time of the impactor must be known to this accuracy in order to forecast the impact at all, and to determine how to affect its velocity.[citation needed]

Nuclear weapons

Detonating a nuclear explosion above the surface (or on the surface or beneath it) of an NEO would be one option, with the blast vaporizing part of the surface of the object and nudging it off course with the reaction. This is a form of nuclear pulse propulsion. Even if not completely vaporized, the resulting reduction of mass from the blast combined with the radiation blast and rocket exhaust effect from ejecta could produce positive results.

Another proposed solution is to detonate a series of smaller nuclear bombs alongside the asteroid, far enough away as not to fracture the object. Providing this was done far enough in advance, the relatively small forces from any number of nuclear blasts could be enough to alter the object's trajectory enough to avoid an impact. The 1964 book Islands in Space, calculates that the nuclear megatonnage necessary for several deflection scenarios exists.[15] In 1967, graduate students under Professor Paul Sandorff at the Massachusetts Institute of Technology designed a system using rockets and nuclear explosions to prevent a hypothetical impact on Earth by the asteroid 1566 Icarus. This design study was later published as Project Icarus[16][17][18] which served as the inspiration for the 1979 film Meteor.[18][19][20]

Kinetic impact

The hurling of a massive object at the NEO, such as a spacecraft or another near-Earth object, is another violent possibility. A small asteroid or large mass in a stable high-Earth orbit would have tremendous kinetic energy stored up. With the addition of some thrust from mounted rockets (plasma or otherwise), it could be used like a stone from a slingshot to deflect the incoming threat.

An alternative means of deflecting an asteroid is to attempt to directly alter its momentum by sending a spacecraft to collide with the asteroid.

The European Space Agency is already studying the preliminary design of a space mission able to demonstrate this futuristic technology. The mission, named Don Quijote, is the first real asteroid deflection mission ever designed.

In the case of 99942 Apophis it has been demonstrated by ESA's Advanced Concepts Team that deflection could be achieved by sending a simple spacecraft weighing less than one ton to impact against the asteroid. During a trade-off study one of the leading researchers argued that a strategy called 'kinetic impactor deflection' was more efficient than others.

Asteroid gravitational tractor

One more alternative to explosive deflection is to move the asteroid slowly over a time. Tiny constant thrust accumulates to deviate an object sufficiently from its predicted course. Edward T. Lu and Stanley G. Love have proposed using a large heavy unmanned spacecraft hovering over an asteroid to gravitationally pull the latter into a non-threatening orbit. The spacecraft and the asteroid mutually attract one another. If the spacecraft counters the force towards the asteroid by, e.g., an ion thruster, the net effect is that the asteroid is accelerated towards the spacecraft and thus slightly deflected from its orbit. While slow, this method has the advantage of working irrespective of the asteroid composition or spin rate – rubble pile asteroids would be difficult or impossible to deflect by means of nuclear detonations while a pushing device would be hard or inefficient to mount on a fast rotating asteroid. A gravity tractor would likely have to spend several years beside the asteroid to be effective.

Ion beam shepherd

Another "contactless" asteroid deflection technique has been recently proposed by C.Bombardelli and J.Peláez from the Technical University of Madrid. The method involves the use of a low divergence ion thruster pointed at the asteroid from a nearby hovering spacecraft. The momentum transmitted by the ions reaching the asteroid surface produces a slow but continuous force that can deflect the asteroid in a similar way as done by the gravity tractor but with a lighter spacecraft.

Use of focused solar energy

NASA study of a solar sail. The sail would be 0.5 km wide.

H. Jay Melosh proposed to deflect an asteroid or comet by focusing solar energy onto its surface to create thrust from the resulting vaporization of material, or to amplify the Yarkovsky effect. Over a span of months or years enough solar radiation can be directed onto the object to deflect it.

This method would first require the construction of a space station with a system of gigantic lens and magnifying glasses near the Earth. Then the station would be transported toward the Sun.

Mass driver

A mass driver is an (automated) system on the asteroid to eject material into space thus giving the object a slow steady push and decreasing its mass. A mass driver is designed to work as a very low specific impulse system, which in general uses a lot of propellant, but very little power.

The idea is that when using local material as propellant, the amount of propellant is not as important as the amount of power, which is likely to be limited.

Another possibility is to use a mass driver on the moon aimed at the NEO to take advantage of the moon's orbital velocity and inexhaustible supply of "rock bullets".

Conventional rocket motor

Attaching any spacecraft propulsion device would have a similar effect of giving a steady push, possibly forcing the asteroid onto a trajectory that takes it away from Earth. An in-space rocket engine that is capable of imparting an impulse of 106 N·s (E.g. adding 1 km/s to a 1000 kg vehicle), will have a relatively small effect on a relatively small asteroid that has a mass of roughly a million times more. Chapman, Durda, and Gold's white paper[21] calculates deflections using existing chemical rockets delivered to the asteroid.

Other proposals

  • Non-conventional engines, such as VASIMR
  • Wrapping the asteroid in a sheet of reflective plastic such as aluminized PET film as a solar sail
  • "Painting" or dusting the object with titanium dioxide (white) or soot (black) to alter its trajectory via the Yarkovsky effect.
  • Planetary scientist Eugene Shoemaker in 1996 proposed[22] deflecting a potential impactor by releasing a cloud of steam in the path of the object, hopefully gently slowing it. Nick Szabo in 1990 sketched[23] a similar idea, "cometary aerobraking", the targeting of a comet or ice construct at an asteroid, then vaporizing the ice with nuclear explosives to form a temporary atmosphere in the path of the asteroid.
  • Attaching a tether and ballast mass to the asteroid to alter its trajectory by changing its center of mass.[24]
  • Laser ablation
  • Magnetic Flux Compression

Deflection technology concerns

Carl Sagan, in his book Pale Blue Dot, expressed concerns about deflection technology: that any method capable of deflecting impactors away from Earth could also be abused to divert non-threatening bodies toward the planet. Considering the history of genocidal political leaders and the possibility of the bureaucratic obscuring of any such project's true goals to most of its scientific participants, he judged the Earth at greater risk from a man-made impact than a natural one. Sagan instead suggested that deflection technology should only be developed in an actual emergency situation.

Analysis of the uncertainty involved in nuclear deflection shows that the ability to protect the planet does not imply the ability to target the planet. A nuclear bomb which changed an asteroid's velocity by 10 meters/second (plus or minus 20%) would be adequate to push it out of an Earth-impacting orbit. However, if the uncertainty of the velocity change was more than a few percent, there would be no chance of directing the asteroid to a particular target.

According to Rusty Schweickart, the gravitational tractor method is also controversial because during the process of changing an asteroid's trajectory the point on Earth where it could most likely hit would be slowly shifted across different countries. It means that the threat for the entire planet would be minimized at the cost of some specific states' security. In Schweickart's opinion, choosing the way the asteroid should be "dragged" would be a tough diplomatic decision.[25]

Planetary defense timeline

  • In their 1964 book, Islands in Space, Dandridge M. Cole and Donald W. Cox noted the dangers of planetoid impacts, both those occurring naturally and those that might be brought about with hostile intent. They argued for cataloging the minor planets and developing the technologies to land on, deflect, or even capture planetoids.[26]
  • In the 1980s NASA studied evidence of past strikes on planet Earth, and the risk of this happening at our current level of civilization. This led to a program that maps which objects in the Solar System both cross Earth's orbit and are large enough to cause serious damage if they ever hit.
  • In the 1990s, US Congress held hearings to consider the risks and what needed to be done about them. This led to a US$3 million annual budget for programs like Spaceguard and the near-Earth object program, as managed by NASA and USAF.
  • In 2005 the world's astronauts published an open letter through the Association of Space Explorers calling for a united push to develop strategies to protect Earth from the risk of a cosmic collision.[27]
  • It is currently (as of late 2007) believed that there are approximately 20,000 objects capable of crossing Earth's orbit and large enough (140 meters or larger) to warrant concern.[28] On the average, one of these will collide with Earth every 5,000 years, unless preventative measures are undertaken.[29] It is now anticipated that by year 2008, 90% of such objects that are 1 km or more in diameter will have been identified and will be monitored. The further task of identifying and monitoring all such objects of 140m or greater is expected to be complete around 2020.[29]
  • The Catalina Sky Survey[30] (CSS) is one of NASA´s four funded surveys to carry out a 1998 U.S. Congress mandate to find and catalog by the end of 2008, at least 90 percent of all near-Earth objects (NEOs) larger than 1 kilometer across. CSS discovered 310 NEOs in 2005, 400 in 2006 and the record will be broken with 450 NEOs found in 2007. In doing this survey they discovered on November 20, 2007, an asteroid, designated 2007 WD5, which initially was estimated to have a chance of hitting Mars on January 30, 2008, but further observations during the following weeks allowed NASA to rule out an impact.[31] NASA estimated a near miss by 26,000 km.[32]

Fictional representations

Asteroid or comet impacts are a common subgenre of disaster fiction, and such stories typically feature some attempt—successful or unsuccessful—to prevent the catastrophe. Most involve trying to destroy or explosively redirect an object, perhaps understandably from the direction of dramatic interest. (See also Asteroids in fiction#Collisions with Earth).


  • Meteor (1979): A series of orbital platforms armed with nuclear missiles are used to deflect an asteroid.
  • Starship Troopers (1997): Insect-like aliens launch an asteroid at Earth, obliterating Buenos Aires. Shortly afterward, orbital defenses are constructed to destroy any future asteroids the aliens may send.
  • Armageddon (1998): A pair of newly-modified space shuttles are used to drill a hole in an asteroid and plant a nuclear bomb.
  • Deep Impact (1998): A manned spacecraft plants a number of nuclear bombs on a comet and is partially successful.
  • Earthstorm (2006): Asteroid impact on the lunar surface and a resulting debris storm that strikes the Earth, inflicting severe damage. Scientists, along with a bombing expert, bind the Moon's core, thereby avoiding a global catastrophe.


  • Halo book series (2001–2003): Large orbital defense platforms armed with weapons known as MAC cannons, or SUPER-MAC cannons, used in the defense of Reach and other human colonies against a Genocidal race known as the Covenant.
  • The Mote in God's Eye (1974): Features the examination of an alien war that culminates in the use of asteroids for planetary bombardment and the near extinction of the warring species. Written by Larry Niven and Jerry Pournelle.
  • Lucifer's Hammer (1977): A comet, which was initially thought unlikely to strike, hits the Earth, resulting in the end of civilization and a decline into tribal warfare over food and resources. Written by Larry Niven and Jerry Pournelle.
  • Shiva Descending (1980): A swarm of meteors is falling on Earth, but a giant comet, Shiva, is still coming. Written by Gregory Benford and William Rotsler.
  • Footfall (1985): An alien race uses controlled meteorite strikes as well as a large asteroid superweapon against Earth. Written by Larry Niven and Jerry Pournelle.
  • The Hammer of God (1993): A spacecraft is sent to divert a massive asteroid by using thrusters. Written by Arthur C. Clarke.
  • Moonfall (1998): A comet is in collision course with the Moon. After the collision, the debris start falling on Earth. Written by Jack McDevitt.
  • Nemesis (1998): The US government gathers a small team, including a British astronomer, with instructions to find and deflect an asteroid already targeted at North America by the Russians. Written by British astronomer Bill Napier.
  • Terraforming Earth (2001): An asteroid impact wipes out most life on Earth. The only remaining humans are a small group of clones on an automated moon base, tasked with rebuilding civilization. Written by Jack Williamson.


  • Star Trek: In "The Paradise Syndrome" (1968), an amnesiac Kirk finds a centuries-old obelisk which has a deflector beam built in to deflect an asteroid coming to wipe out a primitive race.
  • The Simpsons: In "Bart's Comet" (1995), Bart discovers a comet that is heading directly for Springfield. The town attempts to destroy it with a rocket, but it misses. The comet ends up being destroyed by an extra thick layer of pollution over the city.
  • Cowboy Bebop: The series shows an Earth with a shattered moon and several of its fragments remaining in Earth's orbit. The episode "Hard Luck Woman" (1998) focuses on Ed's father, who is constantly updating Earth's geographical map by tracking moon fragments that fall on Earth.
  • Asteroid, a 1998 NBC TV movie, features two large asteroid fragments on collision courses with the Earth. The U.S. government attempts to break the larger of the two fragments apart with airborne lasers.
  • Futurama: The episode "A Big Piece of Garbage" (1999) features a large space object on a collision course with Earth which turns out to be a giant ball of garbage launched into space by New York around 2052. Residents of New New York first try blowing up the ball to destroy it but fail as the rocket is absorbed by the ball. They then deflect it using a newly created near-identical garbage ball.
  • Power Rangers: Lightspeed Rescue: In "The Omega Project" (2000), a meteor is sent towards Earth by evil space aliens, but is blown up by Omegazords.
  • Star Trek: Enterprise: The episode "Terra Prime" (2001) features a domestic xenophobic terrorist organization taking control of the Large Veteron Array on Mars for the purpose of threatening to destroy Starfleet Command. To initiate an undetected sneak attack, members of the Enterprise use a shuttlepod to hide in the wake of an ice asteroid which was intentionally redirected by the Array years earlier to impact with Mars in order to help with terraforming. There is an implied threat that if the terrorists did not maneuver the asteroid correctly, it might accidentally hit near the Mars colony. The asteroid does hit in the correct location, with the crew on the shuttlepod surviving by breaking away at the last moment, successfully remaining undetected.[33]
  • Stargate SG-1: The episode "Fail Safe" (2002) features an asteroid on a collision course with the Earth.
  • Stratos 4 (2003): In this anime, a two-staged space and air defense network is established in order to prevent a large group of comets colliding with Earth.
  • Impact Earth (2007) (a.k.a. Futureshock: Comet): A comet fragment strike in the Atlantic Ocean destroys Shannon Airport, Ireland with a tsunami. They discover it was from a long-period comet that was a Sun Grazer and then discover that it was only a small part and the rest was coming a year later. There is an argument between the main hero scientist as to the efficacy of a nuclear deflection strategy, but they discover in the nick of time that a nuclear bomb would make it worse, so they implement an evacuation strategy and allow it to hit, in Pittsburgh.
  • Danny Phantom: The series finale, "Phantom Planet" (2007) involved a giant asteroid of the fictional element ecto-ranium from the rings of Saturn almost collide with Earth. This was solved when ghosts had made the planet intangible, hence the title.
  • The Sarah Jane Adventures: In "Whatever Happened to Sarah Jane?" (2007), a meteor on a collision course with the Earth is ultimately deflected back into space by Sarah Jane's alien computer, Mr. Smith.
  • Meteor (2009): A large earth-grazing meteor enters the Earth's atmosphere for several minutes and is ultimately deflected back into space using a combined nuclear attack by the United States, Russia, and China.


  • Asteroids by Atari (1979): The object of the game is to shoot and destroy asteroids and saucers while not colliding with either, or being hit by the saucers' counter-fire.
  • Outpost (1994) and Outpost 2 (1997): The player of these two colonization PC games from Sierra Entertainment is given the task of building and managing a space colony in the aftermath of humanity's certain extinction caused by an asteroid collision.
  • The Dig (1995): In this adventure PC game from LucasArts, three of five astronauts assigned to blow an asteroid off-course are transported to a distant world.
  • Homeworld (1999): At the outskirts of the Hiigaran system, the Taiidan attempted to destroy the Kushan Mothership in a last-ditch effort using a large asteroid (somewhere between 15 and 20 km across) with an engine on its back. The asteroid had enough mass and kinetic energy to completely vaporize anything it collided with and was capable of withstanding the combined firepower of the whole Kushan fleet for minutes.
  • Submarine TITANS (2000): A real time strategy game by Ellipse Studios in which the Earth is devastated in 2047 by the impact of the Clark Comet and the attached Silicon spacecraft. The impact of the Clark Comet also deposits significant amounts of the fictional element Corium 276, which factors heavily into both the gameplay and the plot of Submarine TITANS.
  • Ace Combat 04: Shattered Skies (2001): In this combat flight simulator for the PlayStation 2 by Namco, a railgun battery is used in an attempt to destroy a massive asteroid with limited success.
  • Advance Wars: Days of Ruin (2008): Almost 90% of mankind has been killed off following devastating meteor strikes which have destroyed much of civilization and caused a massive dust cloud to blot out the Sun. The player takes the role of a military leader and tries to protect the survivors in the ruins of civilization.
  • Mass Effect (2007): The "Bring Down the Sky" expansion features an alien extremist group that attempts to hijack an asteroid station and set it on a collision course with a human colony.
  • "Rage (video game)" (2011): Asteroid 99942 Apophis impacts the Earth and the technology used to ensue mankind's survival is to keep people in cryogenic sleep until the Earth was safe again

See also


  1. ^ "Report of the Task Force on potentially hazardous Near Earth Objects". British National Space Center. Retrieved 2008-10-21. [dead link], p. 12.[dead link]
  2. ^ a b Morrison, D., 1992, The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop, NASA, Washington, D.C.
  3. ^ Shoemaker, E.M., 1995, Report of the Near-Earth Objects Survey Working Group, NASA Office of Space Science, Solar System Exploration Office
  4. ^ National Academy of Sciences. 2010.Defending Planet Earth: Near-Earth Object Surveys and Hazard Mitigation Strategies: Final Report. Washington, DC: The National Academies Press. Available at:
  5. ^ Stokes, GStokes, G.; J. Evans (18–25 July 2004). "Detection and discovery of near-Earth asteroids by the linear program". 35th COSPAR Scientific Assembly. Paris, France. pp. 4338. Retrieved 2007-10-23. 
  6. ^ "Lincoln Near-Earth Asteroid Research (LINEAR)". National Aeronautics and Space Administration. 23 October 2007. 
  7. ^ "The Spacewatch Project". Retrieved 2007-10-23. 
  8. ^ "Near-Earth Objects Search Program". National Aeronautics and Space Administration. 23 October 2007. 
  9. ^ "NASA Releases Near-Earth Object Search Report". National Aeronautics and Space Administration. Retrieved 2007-10-23. 
  10. ^ David Morrison. "NASA NEO Workshop". National Aeronautics and Space Administration. 
  11. ^ Hearing Charter: Near-Earth Objects: Status of the Survey Program and Review of NASA's 2007 Report to Congress | SpaceRef Canada – Your Daily Source of Canadian Space News
  12. ^ We Saw It Coming: Asteroid Monitored from Outer Space to Ground Impact Newswise, Retrieved on March 26, 2009.
  13. ^ Predicting Apophis' Earth Encounters in 2029 and 2036
  14. ^ "Why we have Asteroid "Scares"". Spaceguard UK.  (Original Site is no longer available, see Archived Site at [1])
  15. ^ Islands in Space, Dandridge M. Cole and Donald W. Cox, pp. 126–127.
  16. ^ Kleiman Louis A., Project Icarus: an MIT Student Project in Systems Engineering, Cambridge, Massachusetts : MIT Press, 1968
  17. ^ "Systems Engineering: Avoiding an Asteroid", Time Magazine, June 16, 1967.
  18. ^ a b Day, Dwayne A., "Giant bombs on giant rockets: Project Icarus", The Space Review, Monday, July 5, 2004
  19. ^ 'Project Icarus
  20. ^ "MIT Course precept for movie", The Tech, MIT, October 30, 1979
  21. ^ [2]
  22. ^ --in a lecture to the Arizona Geological Society in 12-96.
  23. ^
  24. ^ David French (October 2009). "Near-Earth Object Threat Mitigation Using a Tethered Ballast Mass". J. Aerosp. Engrg.. 
  25. ^ Madrigal, Alexis (16 December 2009). "Saving Earth From an Asteroid Will Take Diplomats, Not Heroes". WIRED. Retrieved 17 December 2009. 
  26. ^ Islands in Space, Dandridge M. Cole and Donald W. Cox, pp. 7–8.
  27. ^ "Astronauts push for strategies, spacecraft to prevent calamitous asteroid strike". Pittsburgh Post-Gazette. November 28, 2005. Retrieved 2008-01-18. 
  28. ^ "Subcommittee Questions NASA’s Plan for Detecting Hazardous Asteroids". 
  30. ^ Catlalina Sky Survey website
  31. ^ "Catalina Sky Survey Discovers Space Rock That Could Hit Mars". Retrieved 2007-12-22. 
  32. ^ "Recently Discovered Asteroid Could Hit Mars in January". Retrieved 2007-12-22. 
  33. ^


  • Luis Alvarez et al. 1980 paper in Science magazine on the great mass extinction 65 million years ago that led to the proliferation of mammal species such as the rise of the human race, thanks to asteroid-impact, a controversial theory in its day, now generally accepted.
  • Izzo, D., Bourdoux, A., Walker, R. and Ongaro, F.; "Optimal Trajectories for the Impulsive Deflection of NEOs"; Paper IAC-05-C1.5.06, 56th International Astronautical Congress, Fukuoka, Japan, (October 2005). Later published in Acta Astronautica, Vol. 59, No. 1-5, pp. 294–300, April 2006, available in – The first scientific paper proving that Apophis can be deflected by a small sized kinetic impactor.
  • Clark R. Chapman, Daniel D. Durda & Robert E. Gold (February 24, 2001) Impact Hazard, a Systems Approach, white paper on public policy issues associated with the impact hazard, at
  • Dandridge M. Cole and Donald W. Cox. 1964. Islands in Space: The Challenge of the Planetoids Philadelphia: Chilton. ASIN: B0007DZSR0. First major book on asteroids, covering threat of impact and feasibility of deflection or even capture. Cox and Chestek (following) is a later revision of this book.
  • Donald W. Cox, and James H. Chestek. 1996. Doomsday Asteroid: Can We Survive? New York: Prometheus Books. ISBN 1-57392-066-5. (Note that despite its sensationalist title, this is a good treatment of the subject and includes a nice discussion of the collateral space development possibilities.)
  • David Morrison Is the Sky Falling?, Skeptical Inquirer 1997.
  • David Morrison, Alan W Harris, Geoff Summer, Clark R. Chapman, & Andrea Carusi Dealing with Impact Hazard, 2002 technical summary
  • Russell L. Schweickart, Edward T. Lu, Piet Hut and Clark R. Chapman; "The Asteroid Tugboat"; Scientific American (November 2003).
  • Kunio M. Sayanagi "How to Deflect an Asteroid" Ars Technica (April 2008).
  • Edward T. Lu and Stanley G. Love A Gravitational Tractor for Towing Asteroids;

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