TY - JOUR
T1 - Asteroid (101955) 1999 RQ36: Spectroscopy from 0.4 to 2.4 μm and meteorite analogs
AU - Clark, Beth Ellen
AU - Binzel, Richard P.
AU - Howell, Ellen S.
AU - Cloutis, Edward A.
AU - Ockert-Bell, Maureen
AU - Christensen, Phil
AU - Barucci, Maria Antonietta
AU - DeMeo, Francesca
AU - Lauretta, Dante S.
AU - Connolly, Harold
AU - Soderberg, Alicia
AU - Hergenrother, Carl
AU - Lim, Lucy
AU - Emery, Josh
AU - Mueller, Michael
PY - 2011/12/1
Y1 - 2011/12/1
N2 - We present reflectance spectra from 0.4 to 2.4 μm of Asteroid
(101955) 1999 RQ36, the target of the OSIRIS-REx spacecraft mission. The
visible spectral data were obtained at the McDonald Observatory 2.1-m
telescope with the ES2 spectrograph. The infrared spectral data were
obtained at the NASA Infrared Telescope Facility using the SpeX
instrument. The average visible spectrum is combined with the average
near-infrared wavelength spectrum to form a composite spectrum. We use
three methods to constrain the compositional information in the
composite spectrum of Asteroid (101955) 1999 RQ36 (hereafter RQ36).
First, we perform a least-squares search for meteorite spectral analogs
using 15,000 spectra from the RELAB database. Three most likely
meteorite analogs are proposed based on the least-squares search. Next,
six spectral parameters are measured for RQ36 and their values are
compared with the ranges in parameter values of the carbonaceous
chondrite meteorite classes. A most likely meteorite analog group is
proposed based on the depth of overlap in parameter values. The results
of the least-squares search and the parametric comparisons point to CIs
and/or CMs as the most likely meteorite analogs for RQ36, and COs and
CHs as the least likely. RQ36 has a spectrally “blue”
continuum slope that is also observed in carbonaceous chondrites
containing magnetite. We speculate that RQ36 is composed of a
“CM1”-like material. Finally, we compare RQ36 to other
B-type asteroids measured by Clark et al. (Clark, B.E. et al. [2010]. J.
Geophys. Res. 115, E06005). The results of this comparison are
inconclusive. RQ36 is comparable to Themis spectral properties in terms
of its albedo, visible spectrum, and near-infrared spectrum from 1.1 to
1.45 μm. However, RQ36 is more similar to Pallas in terms of its
near-infrared spectrum from 1.6 to 2.3 μm. Thus it is possible that
B-type asteroids form a spectral continuum and that RQ36 is a
transitional object, spectrally intermediate between the two
end-members. This is particularly interesting because Asteroid 24 Themis
was recently discovered to have H2O ice on the surface
(Rivkin, A., Emery, J. [2010]. Nature 464, 1322-1323; Campins, H. et al.
[2010a]. Nature 464, 1320-1321).
AB - We present reflectance spectra from 0.4 to 2.4 μm of Asteroid
(101955) 1999 RQ36, the target of the OSIRIS-REx spacecraft mission. The
visible spectral data were obtained at the McDonald Observatory 2.1-m
telescope with the ES2 spectrograph. The infrared spectral data were
obtained at the NASA Infrared Telescope Facility using the SpeX
instrument. The average visible spectrum is combined with the average
near-infrared wavelength spectrum to form a composite spectrum. We use
three methods to constrain the compositional information in the
composite spectrum of Asteroid (101955) 1999 RQ36 (hereafter RQ36).
First, we perform a least-squares search for meteorite spectral analogs
using 15,000 spectra from the RELAB database. Three most likely
meteorite analogs are proposed based on the least-squares search. Next,
six spectral parameters are measured for RQ36 and their values are
compared with the ranges in parameter values of the carbonaceous
chondrite meteorite classes. A most likely meteorite analog group is
proposed based on the depth of overlap in parameter values. The results
of the least-squares search and the parametric comparisons point to CIs
and/or CMs as the most likely meteorite analogs for RQ36, and COs and
CHs as the least likely. RQ36 has a spectrally “blue”
continuum slope that is also observed in carbonaceous chondrites
containing magnetite. We speculate that RQ36 is composed of a
“CM1”-like material. Finally, we compare RQ36 to other
B-type asteroids measured by Clark et al. (Clark, B.E. et al. [2010]. J.
Geophys. Res. 115, E06005). The results of this comparison are
inconclusive. RQ36 is comparable to Themis spectral properties in terms
of its albedo, visible spectrum, and near-infrared spectrum from 1.1 to
1.45 μm. However, RQ36 is more similar to Pallas in terms of its
near-infrared spectrum from 1.6 to 2.3 μm. Thus it is possible that
B-type asteroids form a spectral continuum and that RQ36 is a
transitional object, spectrally intermediate between the two
end-members. This is particularly interesting because Asteroid 24 Themis
was recently discovered to have H2O ice on the surface
(Rivkin, A., Emery, J. [2010]. Nature 464, 1322-1323; Campins, H. et al.
[2010a]. Nature 464, 1320-1321).
U2 - 10.1016/j.icarus.2011.08.021
DO - 10.1016/j.icarus.2011.08.021
M3 - Article
SN - 0019-1035
VL - 216
SP - 462
EP - 475
JO - Icarus
JF - Icarus
IS - 2
ER -