¹Z.A. Landsman, ¹H. Campins, ²N. Pinilla-Alonso, ³J. Hanuš, ⁴V. Lorenzi
¹Department of Physics, University of Central Florida, 4111 Libra Drive, PS 430, Orlando, FL 32826
²Department of Earth and Planetary Sciences, University of Tennessee, 1412 Circle Drive, Knoxville, TN 37996
³UNS-CNRS-Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France
⁴Fundación Galileo Galilei-INAF, Rambla José Ana Fernández Pérez 7, 38712, Breña Baja, TF, Spain

We obtained 2-4 μμm spectra of six M-type asteroids using the SpeX spectrograph at NASA’s Infrared Telescope Facility. We find evidence for hydrated minerals on all six asteroids, including two that were previously thought to be dry. One of our targets, (216) Kleopatra, shows rotational variability in the depth of its 3-μμm feature. We also studied three of these asteroids in the 0.8 – 2.4 μμm range using the NICS instrument at the Telescopio Nazionale Galileo (TNG) in La Palma, Spain. The discovery of spectral signatures of hydrated minerals on so many M-types is difficult to reconcile with a highly thermally evolved composition. It has been suggested that the hydrated minerals could have been delivered to M-types via impacts with primitive objects, or that the M-types may actually have primitive compositions that are not represented in meteorite collections. Understanding the origin and type of hydration on these asteroids will help determine which of these interpretations is correct.

Reference
Landsman ZA, Campins H, Pinilla-Alonso N, Hanuš J, Lorenzi V (2015) A new investigation of hydration in the M-type asteroids. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2015.01.021]
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