E-type asteroid 2867 Steins: flyby target for RosettaReport as inadecuate

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1 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides 2 Astronomical Institute of the Romanian Academy 3 LESIA - Laboratoire d-études spatiales et d-instrumentation en astrophysique 4 EAPS - Department of Earth, Atmospheric and Planetary Sciences MIT, Cambridge

Abstract : Aims. The mineralogy of the asteroid 2867 Steins was investigated in the framework of a ground-based science campaign dedicated to the future encounter with Rosetta spacecraft. Methods. Near-infrared NIR spectra of the asteroid in the 0.8−2.5 μm spectral range have been obtained with SpeX-IRTF in remoteobserving mode from Meudon, France, and Cambridge, MA, in December 2006 and in January and March 2007. A spectrum with a combined wavelength coverage from 0.4 to 2.5 μm was constructed using previously obtained visible data. To constrain the possible composition of the surface, we constructed a simple mixing model using a linear areal mix of three components obtained from the RELAB database. A space-weathering model was applied to the aubrite ALH-78113 spectrum. Results. The four new NIR spectra reveal no major absorption features. The best-fit model for the constructed visible-plus-NIR spectrum is represented by a mixture of 57% enstatite, 42% oldhamite, and 1% orthopyroxene. These results place Steins in a subdivision of the E-type class with objects like Angelina, Eger, and Nereus. This group is not sampled by the current collection of aubrite meteorites. Interestingly, the reddened aubrite spectrum also provides a good match to the Steins VNIR spectrum.

Keywords : minor planets asteroids techniques: spectroscopic methods: observational

Author: Dan Alin Nedelcu - Mirel Birlan - Pierre Vernazza - Richard P. Binzel - Marcello Fulchignoni - Maria Antonietta Barucci -

Source: https://hal.archives-ouvertes.fr/


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