Near Earth Object Program
Impacts throughout history
Modern Day Risks
The world received an impressive reminder of the dangers of asteroids on the morning of February 15, 2013, when an asteroid exploded over the town of Chelyabinsk, Russia [12, Fig 2]. The resulting explosion, or superbolide, damaged over 7,000 buildings, and injured more than 1,500 people . Fortunately, there were no fatalities. The asteroid that caused the damage was only 17 to 20 meters in size, a mere baby when compared to Apophis. Still, even this small asteroid became a 440 kiloton air-blast bomb upon entering the Earth’s atmosphere  (Fig. 2).
The potential effects of an asteroid collision are clear enough. What remains is the question of what to do when the Earth is faced with its next certain encounter. Of course, there is evacuation and other disaster preparation, but why not attempt to avoid the collision to begin with? It turns out, if given enough of a head start, it takes only a relatively small course adjustment to prevent an impending collision. And, engineers are already at work, devising theoretical plans of action to achieve this very goal.
The Paintball Approach
The Gravity Tractor
-  NASA. (2013). Near Earth Object Program FAQ [Online]. Available: http://neo.jpl.nasa.gov/faq
-  A. Chamberlain, NASA. (2013, February 7). NEO Discovery Statistics [Online]. Available:
-  R. P. Binzel. (2004). Torino Impact Scale [Online]. Available: http://impact.arc.nasa.gov/torino.cfm
-  T. Philips. (2008). The Tunguska Impact — 100 Years Later [Online]. Available: http://science.nasa.gov/science-news/science-at-nasa/2008/30jun_tunguska/
-  University of Texas, Austin. (2000, December 25). Yucatan Crater Linked To Mass Extinctions Of Dinosaurs (ScienceDaily) [Online]. Available: http://www.sciencedaily.com/releases/2000/12/001225061758.htm
-  TsarBomba.org. (2013). About Tsar Bomba [Online]. Available: http://www.tsarbomba.org/
-  NASA. (2013, January 10). 99942 Apophis (2004 MN4) Earth Impact Risk Summary [Online].
- Available: http://neo.jpl.nasa.gov/risk/a99942.html
-  D. Yeomans, S. Chesley, P. Choda. (2004, December 24). Near-Earth Asteroid 2004 MN4 Reaches Highest Score To Date On Hazard Scale [Online] Available: http://neo.jpl.nasa.gov/news/news146.html
-  N. J. Bailey, G. G. Swinerd, A. D. Morley, H. G. Lewis. (2006). Near Earth Object impact simulation tool for supporting the NEO mitigation decision making process. Proceedings of the International Astronomical Union [Online]. 2, pp 477-486. Available: http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=998156
-  D. Noland. (2006, November 7). 5 Plans to Head Off the Apophis Killer Asteroid [Online]. Popular
- Mechanics. Available: http://www.popularmechanics.com/science/space/deep/4201569
-  National Geographic News. (2005, January 27). The Deadliest Tsunami in History? [Online].
- Available: http://news.nationalgeographic.com/news/2004/12/1227_041226_tsunami.html
-  D. Yeomans, P. Chodas. (2013, March 1). Additional Details on the Large Fireball Event over Russia on Feb. 15, 2013. NASA. [Online]. Available: http://neo.jpl.nasa.gov/news/fireball_130301.html
-  Russia Beyond the Headlines. (2013, March 5). Meteorite-cause emergency situation regime over in Chelyabinsk region. [Online]. Available: http://rbth.ru/news/2013/03/05/meteorite- caused_emergency_situation_regime_over_in_chelyabinsk_region_23513.html
-  C. Dillow. (2012, April 9). How it Would Work: Destroying an Incoming Killer Asteroid With a Nuclear Blast [Online]. PopSci.com. Available: http://www.popsci.com/technology/article/2012- 04/how-it-would-work-destroying-incoming-killer-asteroid-nuclear-blast
-  N. D. Tyson. (2008, February 19). Neil deGrasse Tyson: Death by Black Hole [Online Video]. Forav.tv. Available: http://fora.tv/2008/02/19/Neil_DeGrasse_Tyson_Death_by_Black_Hole
-  J. Chu. (2012, October 25). Paintballs May Deflect an Incoming Asteroid [Online]. Available: http://web.mit.edu/newsoffice/2012/deflecting-an-asteroid-with-paintballs-1026.html
-  R. Cown. (2005, November 12). Protecting Earth. Science News [Online]. Vol. 168, pp. 310. Society for Science & the Public. Available: http://www.jstor.org.libproxy.usc.edu/stable/4016953