Asteroid (90) Antiope: Another icy member of the Themis family?

    Authors

    K. D. Hargrove; J. P. Emery; H. Campins;M. S. P. Kelley

    Comments

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    Abbreviated Journal Title

    Icarus

    Keywords

    Asteroids; Asteroids, surfaces; Asteroids, composition; Infrared; observations; Ices, IR spectroscopy; SPITZER-SPACE-TELESCOPE; MAIN BELT ASTEROIDS; SPECTROSCOPIC SURVEY; VISIBLE SPECTROSCOPY; WATER-ICE; 65 CYBELE; SPECTROGRAPH; ORGANICS; SPECTRA; SURFACE; Astronomy & Astrophysics

    Abstract

    Many members of the Themis family show evidence of hydration in the form of oxidized iron in phyllosilicates (Florczak, M. et al. [1999]. Astron. Astrophys. Suppl. Ser. 134, 463-471), and OH-bearing minerals (Takir, D., Emery, J.P. [2012]. Icarus 219, 641-654). The largest member, (24) Themis, has H2O ice covering its surface (Campins, H. et al. [2010]. Nature 464, 1320-1321; Rivkin, A.S., Emery, J.P. [2010]. Nature 464, 1322-1323). We have investigated the second largest Themis-family asteroid, (90) Antiope, which Castillo-Rogez and Schmidt (Castillo-Rogez, J.C., Schmidt, B.E. [2010]. Geophys. Res. Lett. 37, L10202) predict to have a composition that includes water ice and organics. We obtained 2-4-mu m spectroscopy of (90) Antiope in 2006 and 2008, and we find an absorption in the 3-mu m region clearly present in our 2008 spectrum and likely in our 2006 spectrum. Both spectra have rounded, bowl-shaped absorptions consistent with those ascribed to water ice as in the spectrum of Asteroid (24) Themis. We also present and compare Spitzer 8-12-mu m 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, J. et al. [2012]. Astron. Astrophys. 537, A73), and Jupiter Trojans (e.g. Emery, J.P., Cruikshank, D.P., Van Cleve, J. [2006]. Icarus 182, 496-512). We conclude that the surface structure of (90) Antiope is most similar to Cybele Asteroid (121) Hermione (Hargrove, K.D. et al. [2012]. Icarus 221, 453-455). (C) 2015 Elsevier Inc. All rights reserved.

    Journal Title

    Icarus

    Volume

    254

    Publication Date

    1-1-2015

    Document Type

    Article

    Language

    English

    First Page

    150

    Last Page

    156

    WOS Identifier

    WOS:000355022000013

    ISSN

    0019-1035

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