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Pasadena CA (JPL) Jan 06, 2014
Several sources confirm that the first discovered asteroid of 2014, designated 2014 AA, entered the Earth's atmosphere late January 1 EST over the mid-Atlantic Ocean. This very small asteroid -- 6 to 9 feet (2 to 3 meters) in size was discovered, and immediately followed up, early on the morning of January 1 by the Catalina Sky Survey operating near Tucson Arizona. (An animation of the discovery images is shown in Figure 1). The asteroid entered the Earth's atmosphere about 21 hours later, and probably broke up.
The high precision astrometry data and rapid follow-up observations provided by the Catalina Sky Survey team made it possible for orbit analysts from NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, California to determine possible Earth impact locations.
Prior to impact, and based upon the Catalina Sky Survey observations, Steve Chesley (JPL) produced a plot of the possible Earth impact locations for asteroid 2014 AA. Chesley's graphic is shown in Figure 2, where the nearly horizontal blue band represents the region of possible impacts.
The geolocation derived by Chesley allowed Peter Brown (University of Western Ontario) and Petrus Jenniskens (SETI Institute) to search the data from low frequency infrasound observation sites of the Comprehensive Nuclear-Test-Ban Treaty Organization.
They found weak signals from stations in Bolivia, Brazil and Bermuda that indicated that the likely impact location was indeed positioned within the predicted impact area. The location of impact, marked with a red dot, is still somewhat uncertain due to observational factors, including atmospheric effects upon the propagation of infrasound signals.
Infrasound stations record ultra low frequency sound waves to monitor the location of atmospheric explosions. These sites often pick up airbursts from small asteroid impacts, commonly called fireballs or bolides. There about a billion near-Earth objects in the size range of 2014 AA, and impacts of comparably-sized objects occur several times each year.
Uncertainties present in the infrasound technique and the very limited amount of optical tracking data be fore impact make it difficult to precisely pinpoint the impact time and location. Even so, Chesley provides the following impact estimate:
Impact time: 2014 Jan. 2 at 4:02 UTC (Jan. 1 at 11:02 pm EST) Impact location coordinates: 11.7 deg N, 319.7 deg E.
This impact information is preliminary and has uncertainties of perhaps a few hundred kilometers in impact location and tens of minutes in impact time.
Prior to impact, the orbit of 2014 AA had a very low inclination (about 1 degree) with respect to the ecliptic plane and an orbit that ranged from 0.9 to 1.3 au from the sun with a period of about 1.2 years.
Thus ends our brief acquaintance with asteroid 2014 AA - from discovery by the Catalina Sky Survey to the infrasound whimpers of its demise in the Earth's atmosphere only 21 hours later.
Near-Earth Object Program Office
Asteroid and Comet Mission News, Science and Technology
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