DETERMINING THE PYROXENE MINERALOGIES OF

1
DETERMINING THE PYROXENE MINERALOGIES OF
NEAR-EARTH, MIDDLE-BELT, AND OUTER-BELT VESTOIDS
Thomas H. Burbine (Department of Astronomy, Mount
Holyoke College, South Hadley, MA 01075, USA,
tburbine_at_mtholyoke.edu), Paul C. Buchanan
(Kilgore College, 1100 Broadway, Kilgore, TX
75662, USA), and Richard P. Binzel (Department of
Earth, Atmospheric, and Planetary Sciences, MIT,
Cambridge, MA 02139, USA)
Introduction Vestoids are objects with
reflectance spectra (Figure 1) similar to 4 Vesta
or HED (howardite, eucrite, and diogenite)
meteorites. Most Vestoids are located near Vesta
in the inner main-belt (2.1-2.5 AU). Vestoids
have also been identified (Table 1) past the 31
resonance (2.5 AU) in the middle- (2.5-2.8 AU)
and outer-belt (2.8-3.3 AU) (Figure 2) and in
near-Earth space (Figure 3). We have derived
(Table 2) the mineralogies of a number of these
Vestoids and compared the calculated mineralogies
to those of HEDs. The pyroxene mineralogy of
1459 Magnya was previously derived (Fs36Wo7-9)
by Hardersen et al. (2004).
Figure 1
eucrite
4 Vesta
Normalized Reflectance
howardite
diogenite
Wavelength (mm)
Table 1. SpeX observations Asteroid
Date (UT) Standard Stars Type
Temperature 1459 Magnya 02/20/01 BS 4486,
Landolt 102-1081, Landolt 98-978
Outer-Belt 132 K 3908 Nyx 09/15/04 Landolt
110-361, 16 Cygnus B, Landolt 93-101, Hyades
64 Amor 237 K 4055 Magellan 04/11/05 Lan
dolt 107-684, FS 27 Amor 188
K 5604 1992 FE 03/29/01 Landolt 98-978, Landolt
102-1081, Landolt 104-483, Landolt
107-684 Aten 227 K 6611 1993
VW 05/10/05 Landolt 102-1081, Landolt 105-56,
Landolt 110-361 Apollo 238 K 21238 1995
WV7 11/11/07 Landolt 93-101, Landolt
113-276 Middle-Belt 166 K 52750
1998 KK17 09/15/04 Landolt 110-361, 16 Cygnus B,
Landolt 93-101, Hyades 64 Apollo 218
K 88188 2000 XH44 02/19/04 Hyades 64, Landolt
98-978, Landolt 102-1081, Landolt
107-684 Amor 227 K 2005
WX 11/22/05 Landolt 115-271, Landolt 93-101,
Hyades 64 Apollo 255 K
Figure 2
21238 1995 WV7
Normalized Reflectance
1459 Magnya
Wavelength (mm)
Figure 3
2005 WX
Table 2. Results Band I temperature
Band II temperature Gaffey et
al. (2002) Burbine et al. (2007) Asteroid
center correction
center correction mineralogy
mineralogy Middle- and Outer-Belt 1459
Magnya 0.9310.002 0.003 1.9550.001
0.030 Fs495Wo104
Fs433Wo101 21238 1995 WV7 0.9260.002 0.002
1.8940.003 0.024 Fs315Wo84
Fs333Wo61 Near-Earth Asteroids 3908
Nyx 0.930 0.001 1.9540.002 0.011
Fs435Wo94 Fs403Wo81 4055
Magellan 0.925 0.002 1.9330.002 0.020
Fs405Wo74 Fs363Wo71 5604 1992
FE 0.9290.002 0.001 1.9550.002 0.012
Fs445Wo94 Fs393Wo81 6611 1993
VW 0.9400.001 0.001 2.0090.003 0.010
Fs435Wo134 Fs503Wo131 52750 1998
KK17 0.9260.002 0.001 1.9900.003 0.014
Fs545Wo74 Fs423Wo91 88188 2000
XH44 0.925 0.001 1.9800.001 0.012
Fs515Wo74 Fs403Wo91 2005
WX 0.9300.006 0.001 1.9530.011 0.007
Fs425Wo94 Fs393Wo81 If a spectral
slope could not be divided out, the band centers
are actually band minima.
88188 2000 XH44
52750 1998 KK17
Normalized Reflectance
6611 1993 VW
5604 1992 FE
4055 Magellan
3908 Nyx
Wavelength (µm)
2
1459
31
2005 WX
Figure 4a
Figure 6
21238 1995 WV7
1459 Magnya
21238
Fs
52750
Fs
Sine of Inclination
3908
6611
88188
5604
4 Vesta
4055
Figure 5a
Middle- and Outer-Belt
Near-Earth
1459
Figure 5b
Semi-Major Axis (AU)
21238
3908
5604
2005 WX
4055
52750
88188
Figure 4b
Conclusions We have derived the mineralogies of
Vestoids in the middle-belt (21238 1995 WV7),
outer-belt (1459 Magnya), and near-Earth space.
All objects have mineralogies (Figures 5a, 5b,
6a, 6b) conclusion implies that more than one
basaltic body formed in the asteroid belt since
Magnya is located so far from Vesta (Figure 6).
Since 21238 1995 WV7 has a mineralogy consistent
with HEDs, this conclusion implies that 1995 WV7
could be a fragment of Vesta that has crossed the
31 resonance (Figure 6).
Wo
Wo
6611
Middle- and Outer-Belt
Near-Earth
basaltic eucrites
cumulate eucrites
diogenites
howardites
basaltic eucrites
cumulate eucrites
diogenites
howardites
Figures 4a and 4b. The open squares (red points)
are pyroxene mineralogies determined using the
formulas of Gaffey et al. (2002) and the open
circles (blue points) are pyroxene mineralogies
determined using the formulas of Burbine et al.
(2007).
Figures 5a and 5b. The open squares (red points)
are pyroxene mineralogies determined using the
formulas of Gaffey et al. (2002) and the open
circles (blue points) are pyroxene mineralogies
determined using the formulas of Burbine et al.
(2007).