[meteorite-list] Link between the potentially hazardous Asteroid (86039) 1999 NC43 and the Chelyabinsk meteoroid tenuous

From: Matson, Rob D. <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Fri, 27 Mar 2015 20:20:31 +0000
Message-ID: <4A4FA25E4DFE584AA580F4F069F9B440A167B53F_at_EMP-EXMR104.corp.leidos.com>

Hi Shawn,

The presumed association between Chelyabinsk and (86039) 1999 NC43 is
dependent on whose computed orbit you believe for Chelyabinsk. If you
use the Popova-Jenniskens-Emel'yanenko-et al orbit, (86039) is not a
bad match, though the orbital inclinations differ by 2.2 degrees. Of the
dozen or so Chelyabinsk orbital element solutions floating around on the
web, Popova et al's has the highest inclination (4.93 +/- 0.48) and the highest
eccentricity (0.58 +/- 0.02), which are both driving similarity to (86039)
which has i=7.1236, e=0.57914.

If instead you use Nakano (a=1.6223665, e=0.5311191, i=3.87128,
node=326.42524, arg.peri.=109.70844), then there are five other
asteroids with orbits that are a better match to Chelyabinsk, notably
2011 EO40 which has a=1.65413, e=0.54017, e=3.3628.

--Rob

-----Original Message-----
From: Meteorite-list [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Shawn Alan via Meteorite-list
Sent: Friday, March 27, 2015 12:07 PM
To: Meteorite Central
Subject: [meteorite-list] Link between the potentially hazardous Asteroid (86039) 1999 NC43 and the Chelyabinsk meteoroid tenuous

Hello Listers

For those that cant get enough science, here you go :)

Shawn Alan
IMCA 1633
ebay store http://www.ebay.com/sch/imca1633ny/m.html
Website http://meteoritefalls.com


Link between the potentially hazardous Asteroid (86039) 1999 NC43 and
the Chelyabinsk meteoroid tenuous

Abstract
We explored the statistical and compositional link between Chelyabinsk
meteoroid and potentially hazardous Asteroid (86039) 1999 NC43 to
investigate their proposed relation proposed by Borovi?ka et al.
(Borovi?ka, J., et al. [2013]. Nature 503, 235-237). First, using a
slightly more detailed computation we confirm that the orbit of the
Chelyabinsk impactor is anomalously close to the Asteroid 1999 NC43. We
find ?(1-3) ? 10-4 likelihood of that to happen by chance. Taking the
standpoint that the Chelyabinsk impactor indeed separated from 1999 NC43
by a cratering or rotational fission event, we run a forward probability
calculation, which is an independent statistical test. However, we find
this scenario is unlikely at the ?(10-3-10-2) level. Secondly, we note
that efforts to conclusively prove separation of the Chelyabinsk
meteoroid from (86039) 1999 NC43 in the past needs to meet severe
criteria: relative velocity ?1-10 m/s or smaller, and ?100 km
distance (i.e. about the Hill sphere distance from the parent body). We
conclude that, unless the separation event was an extremely recent
event, these criteria present an insurmountable difficulty due to the
combination of strong orbital chaoticity, orbit uncertainty and
incompleteness of the dynamical model with respect to thermal
accelerations. This situation leaves the link of the two bodies
unresolved and calls for additional analyses. With that goal, we revisit
the presumed compositional link between (86039) 1999 NC43 and the
Chelyabinsk body. Borovi?ka et al. (Borovi?ka, J., et al. [2013].
Nature 503, 235-237) noted that given its Q-type taxonomic
classification, 1999 NC43 may pass this test. However, here we find that
while the Q-type classification of 1999 NC43 is accurate, assuming that
all Q-types are LL chondrites is not. Our experiment shows that not all
ordinary chondrites fall under Q-taxonomic type and not all LL
chondrites are Q-types. Spectral curve matching between laboratory
spectra of Chelyabinsk and 1999 NC43 spectrum shows that the spectra do
not match. Mineralogical analysis of Chelyabinsk (LL chondrite) and (8)
Flora (the largest member of the presumed LL chondrite parent family)
shows that their olivine and pyroxene chemistries are similar to LL
chondrites. Similar analysis of 1999 NC43 shows that its olivine and
pyroxene chemistries are more similar to L chondrites than LL chondrites
(like Chelyabinsk). Analysis of the spectrum using Modified Gaussian
Model (MGM) suggests 1999 NC43 is similar to LL or L chondrite although
we suspect this ambiguity is due to lack of temperature and phase angle
corrections in the model. While some asteroid pairs show differences in
spectral slope, there is no evidence for L and LL chondrite type objects
fissioning out from the same parent body. We also took photometric
observations of 1999 NC43 over 54 nights during two apparitions (2000,
2014). The lightcurve of 1999 NC43 resembles simulated lightcurves of
tumblers in Short-Axis Mode (SAM) with the mean wobbling angle
20?-30?. The very slow rotation of 1999 NC43 could be a result of
slow-down by the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect.
While, a mechanism of the non-principal axis rotation excitation is
unclear, we can rule out the formation of asteroid in disruption of its
parent body as a plausible cause, as it is unlikely that the rotation of
an asteroid fragment from catastrophic disruption would be nearly
completely halted. Considering all these facts, we find the proposed
link between the Chelyabinsk meteoroid and the Asteroid 1999 NC43 to be
unlikely.

Source: http://adsabs.harvard.edu/abs/2015Icar..252..129R
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Received on Fri 27 Mar 2015 04:20:31 PM PDT