2014 AA impact site identified?

Sky and Telescope magazine is reporting that Peter Brown (University of Western Ontario) has made a preliminary identification of the impact site of 2014 AA, the New Year’s Earth impacting asteroid. Or more exactly, Dr. Brown has found the point where 2014 AA disintegrated in the Earth’s atmosphere.

Brown and his group used data from infrasound arrays to detect the ‘noise’ of the explosion. The location of the fireball was triangulated by measuring the time of arrival of the infrasound signal at a number of infrasound arrays around the world. This technique has been used to pinpoint the location of other large fireball events as well as the detonation of nuclear weapons. As reported by S&T, the preliminary location is at 40° west, 12° north or about 1,900 miles (3,000 km) east of Caracas, Venezuela.

The overlap of the white curves, from three marginal infrasound detections, shows where the small asteroid 2014 AA likely hit. However, this preliminary plot does not take winds into account, which might shift the true impact point somewhat further east.
The overlap of the white curves, from three marginal infrasound detections, shows where the small asteroid 2014 AA likely hit. However, this preliminary plot does not take winds into account, which might shift the true impact point somewhat further east.

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The discovery observations have also been posted at the websites of the NASA JPL NEO Project Office and the Catalina Sky Survey.

This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight "streaking" of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona
This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight “streaking” of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona

2014 AA – New Year’s Earth impactor

2014 has started off with fireworks! The first designated asteroid of the year, discovered only half an hour before midnight on New Year’s Eve (Tucson local time) but 6.5 hours into 2014 in Universal (or Greenwich Mean) time by Richard Kowalski of the Mount Lemmon Survey, was an Earth impactor.

Based on 7 astrometric measurements taken over the course of 70 minutes, the Minor Planet Center’s orbit has determined that 2014 AA impacted the Earth around Jan. 2.2 +/- 0.4 UT somewhere along an arc stretching from the eastern Pacific Ocean, southern Nicaragua, Costa Rica, very northern Columbia and Venezuela, a long stretch of the Atlantic Ocean and the African countries of Senegal, Gambia, Mali, Burkina Faso, Niger, Chad and Sudan. Maps of the possible impact points have been produced by Bill Gray and can be found here and here. The most likely impact point is in the Atlantic Ocean off the coast of western Africa.

With an absolute magnitude of ~30.9, 2014 AA was likely a very small asteroid with a diameter on the order of 1-5  meters. Such an object would have posed no danger to the ground though small meteorites may have survived passage through the atmosphere. If it fell in the ocean there is a good chance that no one directly witnessed it though the signature of its resulting fireball may be found in weather satellite images.

This marks the second time that an asteroid was detected in space prior to impact. The first impactor, 2008 TC3, was also found by Rich Kowalski and the Mount Lemmon 1.5-m reflector. That body was observed to fall over northern Sudan and led to the recovery of many meteorites (named Almahata Sitta). More on the fall of 2008 TC3 and Almahata Sitta can be found at this blog (here, here, here, and here), the Meteoritical Bulletin and Wikipedia.

Note, that for every small asteroid discovered before hitting the Earth (of which we’ve seen only two) there are many thousands of similar sized objects (and countless smaller ones) that go undetected until seen as brilliant fireballs or meteors. Hopefully planned upgrades to current asteroid surveys such as the Catalina Sky Survey/Mount Lemmon Survey and future surveys like ATLAS will result in more warning time for incoming asteroids.