Near-Earth Objects (NEOs)
By Floro Mercene
Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth’s neighborhood. Most asteroids are in what is called “the main belt” between Mars and Jupiter. The vast majority of near-Earth asteroids have come from the inner part of the main belt, where their orbits were altered by mutual collisions and by the gravitational influence of Jupiter and Mars.
Although the vast majority of NEOs that enter Earth’s atmosphere disintegrate before reaching the surface, those that are larger than around 30 to 50 meters in size may survive the descent and cause widespread damage in and around their impact sites.
The flyby of asteroid 2012 DA14 on Feb. 15, 2013 was approximately 45 meters across, and the closest known approach to Earth for an object its size, missing our planet by a mere 27, 700 kilometers. Coincidentally, on the same day, a small asteroid (17 meters in size) broke up over the city of Chelyabinsk, Russia. The shock wave it generated shattered glass and injured about 1,200 people.
A comparison to the impact potential of an asteroid the size of 2012 DA14 could be made to the impact of a near-Earth object that occurred in 1908 in Tunguska, Siberia, known as the “Tunguska Event”. This impact of an asteroid just slightly smaller than 2012 DA14 is believed to have flattened about 2,200 square kilometers of a remote forested region in Siberia.
Because of the ongoing search efforts to find nearly all the large NEOs, objects will occasionally be found to be on very close Earth-approaching trajectories. If an object is verified to be on an Earth colliding trajectory, it seems likely that this collision possibility will be known several years prior to the actual event.
(To be continued)