Asteroid Misses Earth to Return in 2013
NASA Articles 3/21/12
By: Chris Capps
An asteroid only spotted after it had already passed by Earth is expected to return in 2013 to miss yet again. But with an object passing by so frequently and so closely as this object, many sky watchers are concerned that it could soon be on a collision course with Earth. The asteroid is expected to pass so closely that it will be between Earth and most orbital satellites and could be seen using binoculars.
The object, nicknamed 2012 DA14 was first spotted on February 22nd when a group of amateur astronomers observed it. While the object was nowhere near large enough to be a threat to civilization as we know it, it is still being tracked for future potential impact. How close is that? That's less than 14,912 miles to be sure. While it's still considered safe, it's making more than a few interested concerned that we could be in for a potential impact at some point in the future. The asteroid's orbit to the sun is very close to Earth's, flying past once every 366.24 days approximately.
2012 DA14 has had its risk assessment updated several times since it was first spotted in February. Currently the closest likely impact event is scaled all the way back to February 16, 2020.
At current estimates there is an approximate 1 in 53,000 chance that 2012 DA14 will impact Earth on that day, and a cumulative risk afterward that there will be an impact at some point before 2044. But when that happens, how big of an event will that be?
Judging from its speed and size, if it were to hit Earth it would be an event similar in size to the low end estimates as the mysterious Tunguska event. The explosion would be equivalent to about 2.3 megatons in the energy released from the explosion. While this isn't as dramatic as some of the asteroids Earth has seen in its long history, it would still be considerable. By comparison, the bomb used in the destruction of Hiroshima was between 13 and 18 kilotons.
When it comes to near Earth asteroids, if this one has been seen only recently, it may have been making close calls with Earth's shared orbit for years. If the object has been passing by us every year in the past, however, it's been doing so undetected. An object capable of producing an explosion far larger than that of Hiroshima passing by Earth is not unheard of. In fact, a number of objects capable of producing explosions of up to several megatons have been spotted flying past Earth or directly in front of it.
The most terrifying close call of the past ten years was likely 2001 YB5, an asteroid measuring between 715 and 1,592 feet. The object was said to be large and dense enough to cause a massive explosion on Earth if it ever struck, and managed to zip past at a distance of only 375,000 miles in 2002.