[meteorite-list] The First Discovered Asteroid of 2014 Collides With The Earth - An Update

[Ron Baalke]

http://neo.jpl.nasa.gov/news/news182a.html

The First Discovered Asteroid of 2014 Collides With The Earth - An Update
NASA/JPL Near-Earth Object Program Office
January 3, 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.

[Figure 1]
This animated GIF shows Asteroid 2014 AA, discovered by the
NASA-sponsored Catalina Sky Survey on Jan. 1, 2014, as it moved across
the sky. This sequence of discovery images was taken between 1:18 and
1:46 a.m. EST (06:18 and 06:46 UTC). The slight streaking of the
asteroid in the image is due to its rapid motion across the background
of s tars as it approached the Earth. The brightness of the asteroid in
these images is between visual magnitude 18.8 and 19.1.
Image credit: CSS/LPL/UA

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.

[Figure 2]
Global map showing possible impact locations of 2014 AA
based on Catalina Sky Survey images (blue band), and probable impact
location based on infrasound data (red dot).
Image credit: Steve Chesley - NASA/JPL

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.

[Figure 3 Graphic]
The nighttime impact of asteroid 2014 AA
Image credit: Paul Chodas - NASA/JPL

NASA's Near-Earth Object Program at NASA Headquarters, Washington,
manages and funds the search, study and monitoring of asteroids and
comets whose orbits periodically bring them close to Earth. JPL manages
the Near-Earth Object Program Office for NASA's Science Mission
Directorate in Washington. JPL is a division of the California Institute
of Technology in Pasadena.