Kelsey D. Hargrove^a, Josh Emery^b, Humberto Campins^a, Michael S.P. Kelley^c
a Physics Department, University of Central Florida, Orlando, FL 32816
^b Earth and Planetary Science Dept. and Planetary Geosciences Institute, University of Tennessee, Knoxville, TN 37996
^c Department of Astronomy, University of Maryland, College Park, MD 20742-2421

Many members of the Themis family show evidence of hydration in the form of oxidized iron in phyllosilicates (Florczak et al. 1999), and OH-bearing minerals (Takir and Emery 2012). The largest member, (24) Themis, has H2O ice covering its surface (Campins et al., 2010 and Rivkin and Emery, 2010). We have investigated the second largest Themis-family asteroid, (90) Antiope, which Castillo-Rogez and Schmidt (2010) predict to have a composition that includes water ice and organics. We obtained 2-4-μm spectroscopy of (90) Antiope in 2006 and 2008, and we find an absorption in the 3-μm region clearly present in our 2008 spectrum and likely in our 2006 spectrum. Both spectra have rounded, bowl-shaped absorptions consistent with those due to water ice as in the spectrum of (24) Themis, but do not uniquely identify water ice. We also present and compare Spitzer 8-12-μm mid-infrared spectra of (24) Themis and (90) Antiope. We find that (90) Antiope is lacking a “fairy castle” dusty surface, which is in contrast to (24) Themis, other Themis family members (Licandro et al. 2012), and Jupiter Trojans (e.g. Emery et al. 2006). We conclude that the surface structure of (90) Antiope is most similar to Cybele asteroid (121) Hermione (Hargrove et al. 2012).

Reference
Hargrove KD, Emery J, Michael HC, Kelley SP (2015) Asteroid (90) Antiope: Another Icy Member of the Themis Family? Icarus (in Press)
Link to Article [doi:10.1016/j.gca.2015.03.007]

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