2014 AA

2014 AA was a small Apollo near-Earth asteroid roughly 2–4 meters in diameter that struck Earth on 2 January 2014.[1] It was discovered on 1 January 2014 by Richard Kowalski at the Mount Lemmon Survey at an apparent magnitude of 19 using a 1.52-meter (60 in) reflecting telescope at Mount Lemmon Observatory.[1] 2014 AA was only observed over a short observation arc of about 70 minutes,[1] and entered Earth's atmosphere about 21 hours after discovery.[3] Nonetheless it remains one of only a few asteroids observed before impact (see Asteroid impact prediction).[4]

2014 AA
2014 AA imaged by the Catalina Sky Survey in January 2014. The asteroid was around one lunar distance from Earth at that time.
Discovery[1]
Discovered byRichard Kowalski
Mount Lemmon Survey (G96)
Discovery date1 January 2014
Designations
2014 AA
Orbital characteristics[2]
Epoch 1 January 2014 (JD 2456658.5)
Uncertainty parameter 9
Observation arc~70 minutes[1]
Aphelion1.4080 AU (210.63 Gm) (Q)
Perihelion0.9163 AU (137.08 Gm) (q)
1.1623 AU (173.88 Gm) (a)
Eccentricity0.2116 (e)
1.25 yr (457.26 d)
324.1460° (M)
0° 47m 14.244s / day (n)
Inclination1.4156° (i)
101.6086° (Ω)
52.3393° (ω)
Earth MOID4.54412×10−7 AU (67.9791 km)
Jupiter MOID3.58092 AU (535.698 Gm)
Physical characteristics
Dimensions~3 meters (10 ft)
Mass~4×104 kg (assumed)
30.9[2]

    Entry
    Probable impact location of near-Earth asteroid 2014 AA based on infrasound data from the Comprehensive Nuclear-Test-Ban Treaty Organization.[3]

    Using a poorly determined orbit, the JPL Small-Body Database listed a 3-sigma solution with impact occurring around 2 January 2014 02:33 UT ± 1 hour and 5 minutes.[5] The Minor Planet Center listed impact as occurring around 2 January 2014 05:00 UT ± 10 hours.[1] Independent calculations by Bill Gray, the Minor Planet Center and Steve Chesley at the Jet Propulsion Laboratory verified that impact was virtually certain.[1]

    The impactor would have been roughly the size of 2008 TC3, which exploded above the Nubian Desert in Sudan on 7 October 2008. Calculations by Chesley suggest the impactor fell somewhere on an arc extending from Central America to East Africa, with a best-fit location just off the coast of West Africa.[1] Calculations by Pasquale Tricarico using the nominal orbit show that 2014 AA entered Earth's shadow cone approximately 40 minutes before entering the atmosphere.[6]

    Infrasound was detected by three stations of the Comprehensive Nuclear-Test-Ban Treaty Organization.[7] Peter Brown and Petrus Jenniskens located weak signals from infrasound stations in Bolivia, Brazil and Bermuda.[3] 2014 AA entered Earth's atmosphere around 03:06 ± 5 min UT,[8] 3,000 km from Caracas, Venezuela, far from any landmass.[7][8] No ships or planes reported witnessing the event.[7] A recalculation of the impact parameters of this meteor based on infrasound recordings gives a longitude of impact of nearly 44º West and a latitude of 11º North, the impact time being 2456659.618 JD UTC.[9] Extensive numerical simulations indicate that, prior to impact, 2014 AA was subjected to a number of secular resonances and it may have followed a path similar to those of the NEOs 2011 GJ3, 2011 JV10, 2012 DJ54, and 2013 NJ4; NEOs in this transient group experience close encounters with the Earth-Moon system at perihelion and Mars at aphelion and could be a dynamical family.[9]

    Other discoveries

    Kowalski previously discovered 2008 TC3, the first asteroid discovered before Earth impact, using the same telescope in October 2008.[7] There are about a billion near-Earth objects in the size range of 2014 AA, and impacts of comparably-sized objects occur several times each year.[3]

    Several years later, 2018 LA was also discovered by the Mount Lemmon Survey, and ended up impacting Earth in southern Botswana in June 2018.

    See also

    References
    1. "MPEC 2014-A02 : 2014 AA". IAU Minor Planet Center. 2 January 2014. Retrieved 2 January 2014. (K14A00A)
    2. "JPL Small-Body Database Browser: (2014 AA)" (last observation: 1 January 2014; arc: 1 day). Jet Propulsion Laboratory. Retrieved 4 April 2016.
    3. "The First Discovered Asteroid of 2014 Collides With The Earth – An Update". NASA/JPL. 3 January 2014. Retrieved 4 January 2014.
    4. "Tiny Asteroid Discovered Saturday Disintegrates Hours Later Over Southern Africa". NASA/JPL. Jet Propulsion Laboratory. Retrieved 4 June 2018.
    5. "JPL Close-Approach Data: (2014 AA)" (last observation: 1 January 2014; arc: 1 day). Retrieved 2 January 2014.
    6. Guido, Ernesto (2 January 2014). "Small asteroid 2014 AA hit the Earth's atmosphere". Associazione Friulana di Astronomia e Meteorologia. Retrieved 2 January 2014.
    7. Beatty, Kelly (2 January 2014). "Small Asteroid 2014 AA Hits Earth". Sky & Telescope. Retrieved 3 January 2014.
    8. Farnocchia, Davide; Chesley, Steven R.; Brown, Peter G.; Chodas, Paul W. (1 August 2016). "The trajectory and atmospheric impact of asteroid 2014 AA". Icarus. 274: 327–333. Bibcode:2016Icar..274..327F. doi:10.1016/j.icarus.2016.02.056.
    9. de la Fuente Marcos, C.; de la Fuente Marcos, R.; Mialle, P. (13 October 2016). "Homing in for New Year: impact parameters and pre-impact orbital evolution of meteoroid 2014 AA". Astrophysics and Space Science. 361 (11): 358 (33 pp.). arXiv:1610.01055. Bibcode:2016Ap&SS.361..358D. doi:10.1007/s10509-016-2945-3.
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