Surface Mineralogy of Mars-Crossing 1747 Wright: Analogous to the H Chondrites

Michael P. Lucas1 and Joshua P. Emery1 (1) Department of Earth and Planetary Sciences, University of Tennessee, 1412 Circle Drive, Knoxville, TN 37996, [email protected]

Introduction Mars-Crosser 1747 Wright Mineral Abundance and Composition

Figure 6. – 1747 Wright and Asteroid dynamical work has suggested that differentiated • Previously classified in visible-light spectral three more asteroids, precursors of metallic (core) and olivine-rich (mantle) interior to the main-belt fragments may have formed in the terrestrial planet region and are surveys as an A-type indicated on the band-band now interlopers to the inner main-belt [1]. Furthermore, recent work [3,6], Sl-type [5], or an plot from [15]. 1747 Wright has suggested that the are the survivors of an Ld-type [6] plots within the field of extended and now largely extinct portion of the that • We found 1747 Wright orthopyroxene (black diamonds), while 1509 existed between 1.7 and 2.1 AU early in history [2] to be a Sw-type (Bus- DeMeo extended Esclangona appears to be (Figure 1). The mineralogy of these relatively close objects hold more clinopyroxene (gray important clues to the dynamical evolution of the inner-Solar System. taxonomy) squares) rich. In particular, a key aspect of asteroid mineralogy is the abundance • Presence of Band I and composition of olivine and pyroxene, which can reveal details near 0.90 µm and regarding the degree (or lack) of igneous differentiation. Figure 3. – VISNIR spectrum of 1747 Wright Band II near 1.9 µm obtained with the SpeX instrument on the NASA Figure 7. – Mars-crosser Pure olivine-rich A-types remain cryptic among the observable strongly indicates the IRTF in low-resolution prism mode. Reflectance 1747 Wright and three asteroids. However, a number of small (<~8 km) asteroids that reside presence of pyroxene more asteroids interior to values normalized to unity at 0.55 µm. Visible data interior to the main-belt (i.e., Hungaria Group, Mars-crossers, near- (black) from SMASS II [5]. the main-belt shown on the Earth asteroids) are thought to be rare olivine-rich A-type asteroids in S-subtypes plot from [16], one or more visible-light taxonomic surveys [3,4,5,6]. Therefore, it is 1509 Esclangona (possibly 1747 Wright & 3352 vital to examine these objects not just in terms of their taxonomic Near-Earth Asteroid (NEA) 3352 McAuliffe McAuliffe) plot outside of types, but also in terms of their detailed mineralogy. Interestingly, the SIV field of ordinary eight presumed A-types interior to the main-belt have recently been • We are interested in chondrites. Ol-Opx mixing shown to be classified as S-type asteroids after further spectral data the mineralogy of line is indicated. was acquired into the near-infrared (NIR) [7,8]. These results are asteroids interior to consistent with spectral studies [9,10] that indicate that two-thirds of the main-belt all near-Earth asteroids (NEAs) belong to the S- or Q-complexes. (Hungaria, MCs, NEAs) These taxonomic types are spectrally analogous to ordinary • Previously classified in Ordinary Chondrite Analogs chondrites [10]. visible-light surveys as Figure 8. – Four asteroids located interior to the Here we present the visible and near-infrared spectrum an A-type [5], or a S- main-belt plotted as Fa mol% vs. ol/(ol+px) ratio, (VISNIR) of the Mars-crossing (MC) asteroid 1747 Wright (a = 1.709 or Sq-type [6] compositional fields from [14], error bars shown AU), heretofore only recorded in visible wavelengths (Figure 3). • We found 3352 Table 3. – Mineralogy and taxonomy for four The spectral type of this asteroid has been uncertain as taxonomic McAuliffe to be a asteroids located interior to the main-belt. surveys have identified 1747 Wright as an A-type [3,6], Sl-type [5], or Figure 4. – VISNIR spectra of NEA 3352 McAuliffe S-type (Bus-DeMeo an Ld-type [6]. We hypothesize that 1747 Wright is relatively olivine- obtained with the SpeX instrument on the NASA extended taxonomy)

rich. We test this hypothesis by performing detailed spectral band IRTF in low-resolution prism mode. parameter analyses (Tables 2 and 3). Spectral Band Parameter Analysis

Observations • Band Parameters measured after  Spectra recorded using SpeX spectrograph [11] at the NASA Infrared dividing by a straight Current and Future Work Telescope Facility (IRTF), remote observations from UTK line continuum  NIR spectral survey of poorly-observed  SpeX low-resolution prism mode to obtain 0.7-2.5 µm spectra (Figure 5) (heretofore only 14 objects) Hungaria  Reduction performed with IDL-based Spextool provided by the IRTF • Band I and II Centers asteroids  S/N ≥400 for 1747; S/N ≥100 for 1509 and 3352 and Depths  To date, acquisition of NIR spectra of 24 • Band Area Ratio (BAR) Hungarias (Table 4) Table 1. – Observational circumstances for three asteroids interior to • Uncertainty for 1747  Separate the mineralogical characteristics the main-belt. derived by measuring of Hungaria family and background band centers and populations depths 10x with  Proposals submitted to record NIR Figure 5. – VISNIR spectra of Hungaria background different order spectra of ≥40 more small (<~8 km) asteroids 1509 Esclangona and 4142 Dersu-Uzala, polynomial fits (2nd Hungarias, focus on background objects example continuum lines shown in red. Inset box through 5th order) and  Constrain the degree of igneous shows continuum removed Band I (lower ½ band) different band ranges differentiation experienced by these with polynomial fit an Band I center for Dersu-Uzala. (e.g. – full band, lower asteroids Asteroids Interior to the Main-belt - Hungarias Spectra offset for clarity. Dersu-Uzala data from Binzel et al. (2004). 1/2 band, lower 1/3 band) Table 2. – Measured spectral band parameters for four objects located interior Acknowledgements Spectral observation of 1747 Wright was performed under proposal 2012B073 at the NASA IRTF and the authors acknowledge the IRTF telescope operators for their to the main-belt (Δ = temperature corrected). assistance. M.P. Lucas would like to acknowledge the Lunar and Planetary Institute (LPI) for a 2013 LPI Career Development Award. Part of the data utilized in this publication were obtained and made available by the The MIT-UH-IRTF Joint Campaign for NEO Reconnaissance. The IRTF is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program. The MIT component of this work is supported by NASA grant 09-NEOO009-0001, and previously by the National Science Foundation under Grant No. 0506716. References Warner et al., 2012 [9] Binzel et al. (2004) Icarus 170, 259-294. [1] Bottke et al. (2006) Nature 439, 821-824. [10] Dunn, T. L. et al. (2013) Icarus 222, 273-282. [2] Bottke et al. (2012) Nature 485, 78-81. [11] Rayner, J. T. et al. (2003) PASP 115, 362-382. Bottke et al., 2012 Figure 2. – Hungaria population [3] Zellner, B. et al. (1985) Icarus 61, 355-416. [12] Sanchez, J. A. et al. (2012) Icarus 220, 36-50. asteroids (~5000) plotted in H vs. a [4] Xu et al. (1995) Icarus 115, 1-35. [13] Burbine, T. H. et al. (2009) Meteoritics & Pl. Sci. 44, 1331-1341. Figure 1. – Evolution of the now [5] Bus, S. J., and Binzel, R. P. (2002) Icarus 159, 146-177. [14] Dunn, T. L. et al. (2010) Icarus 208, 789-797. [6] Lazzaro, D. et al. (2004) Icarus 172, 179-220. [15] Adams, J. B. (1974) J. Geophys. Res. 79, 4829-4836. space. Hungaria family parent 434 [7] DeMeo, F. E. et al. (2009) Icarus 202, 160-180. [16] Gaffey, M. J. et al. (1993) Icarus 106, 573-602. extinct E-belt of asteroids, survivors  Typical errors for Band I center (BI ± 0.01), Band I depth (BIdep ± 0.3), Band II center & ΔBII center (BII ± 0.03), Band II depth & ΔBII depth (BIIdep ± 0.5), Band Area Ratio (BAR) & ΔBAR (BAR ± 0.04) [8] Lucas, M. P. et al. (2012) BAAS 44, No. 5. [17] Thomas, C. A. and Binzel, R. P. (2010) Icarus 205, 419-429. Hungaria (triangle) and family zone [18] Warner, B. D. et al. (2009) Icarus 204, 172-182 are the Hungaria asteroids, from [2].  Asteroid temperatures calculated as in Burbine et al. (2009) (gray curves) indicated, from [18].