Spectral characterization of V-type asteroids - I. Space weathering effects and implications for V-type NEAs
Date Issued
2016
Author(s)
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Brunetto, Rosario
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Kanuchova, Zuzana
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Blanco, Carlo
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Description
Observations have been carried out with the Italian TNG operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF at the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofisica de Canarias (programmes AOT19/DDT4 and AOT20/TAC4). We thank Alvaro Alvarez-Candal, who kindly made the data published in his paper available to us. The research of ZK has been supported by VEGA – The Slovak Agency for Science, Grant No. 2/0032/14. DP and SI acknowledge financial support from the NEOShield-2 project, funded by the European Commission’s Horizon 2020 programme (Contract No. PROTEC- 2-2014-640351).
Abstract
Among main belt asteroids, V-types belonging to Vesta's dynamical family are known as `Vestoids' while those lying outside Vesta's family as `non-Vestoids'. V-types have also been found within the population of Near Earth Asteroids (NEAs). Several questions on Vesta, the V-types, and the Howardite-Eucrite-Diogenite meteorites are still unsolved, such as the genesis of each class/subclass, their evolution and mutual relationship, and the existence of other basaltic parent bodies. We present new NIR (0.8-2.4 μm) spectroscopic observations of seven non-Vestoids, carried out at the Telescopio Nazionale Galileo (TNG - INAF). We derived a number of spectral parameters (BI and BII centres, band separations, and BI slopes) and compared them with available spectra of V-types belonging to different subclasses (102 V-types in total), to highlight possible spectral differences useful to shed light on the questions mentioned above. We also considered the data from ion irradiation experiments performed on different samples of eucrites, simulating space weathering effects. Net discrepancies are seen for the BI slope distributions: NEAs show a distribution strongly different from all other V-type subclasses. Ion irradiation experiments induce strong effects on BI slope values and, as irradiation proceeds, the BI slope of eucrites quickly increases, changing the overall aspect of their VIS-NIR spectra (0.4-2.5 μm). Space weathering may explain the whole range of spectral slopes observed for all V-type subclasses. An exception is represented by NEAs, where moderate space weathering effects are evidenced. We propose that this is due to tidal perturbations exposing `fresh' unweathered surface grains during close encounters with the Earth, as previously found for Q-type NEAs.
Volume
455
Issue
1
Start page
584
Issn Identifier
0035-8711
Ads BibCode
2016MNRAS.455..584F
Rights
open.access
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