Publication Year 2016
Acceptance in OA@INAF 2020-12-21T11:43:55Z
Title Spectral characterization of V-type asteroids - I. Space weathering effects and implications for V-type NEAs
Authors Fulvio, Daniele; PERNA, Davide; IEVA, Simone; Brunetto, Rosario; Kanuchova, Zuzana; et al.
DOI 10.1093/mnras/stv2300
Handle http://hdl.handle.net/20.500.12386/29048
Journal MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Number 455 MNRAS 455, 584–595 (2016) doi:10.1093/mnras/stv2300
Spectral characterization of V-type asteroids – I. Space weathering effects and implications for V-type NEAs
Daniele Fulvio,1‹ Davide Perna,2 Simone Ieva,3 Rosario Brunetto,4 Zuzana Kanuchova,5 Carlo Blanco,6,7 Giovanni Strazzulla6 and Elisabetta Dotto3 1Departamento de F´ısica, Pontif´ıcia Universidade Catolica´ do Rio de Janeiro, Rua Marquesˆ de Sao˜ Vicente 225, 22451-900 Rio de Janeiro, RJ, Brazil 2LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universites,´ UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cite,´ 5 place Jules Janssen, F-92195 Meudon, France 3INAF – Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone, Roma, Italy 4Institut d’Astrophysique Spatiale, CNRS, UMR-8617, Universite´ Paris-Sud, batimentˆ 121, F-91405 Orsay Cedex, France Downloaded from https://academic.oup.com/mnras/article/455/1/584/984768 by guest on 06 November 2020 5Astronomical Institute of the Slovak Academy of Sciences, 059 60 Tatranska´ Lomnica, Slovakia 6INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania, Italy 7Dipartimento di Fisica e Astronomia, Universita` di Catania, Via S. Sofia 78, I-95123 Catania, Italy
Accepted 2015 October 1. Received 2015 October 1; in original form 2015 August 19
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. Key words: methods: laboratory: atomic – techniques: spectroscopic – meteorites, meteors, meteoroids – minor planets, asteroids: individual: Vesta– infrared: general.
Sanctis et al. 2012). The Dawn spacecraft data show that the 1 and 1 INTRODUCTION 2 µm pyroxene signatures (hereafter BI and BII, respectively) are Asteroid (4) Vesta is the largest differentiated main belt object present ubiquitously across Vesta surface and confirm that Vesta showing a basaltic crust. The basaltic composition of its surface surface composition is similar to that of the Howardite–Eucrite– has been discovered by McCord, Adams & Johnson (1970), later Diogenite meteorites (HEDs). Nevertheless, HEDs lithologies are on confirmed by many observations (e.g. McFadden, McCord & present on Vesta with spectral variations at both large and small Pieters 1977; Binzel et al. 1997; Gaffey 1997; Vernazza et al. scale across its surface and, overall, Vesta mineralogy indicates a 2005) and strengthen by the extensive and detailed data provided by complex geological and collisional history (De Sanctis et al. 2012; the Dawn spacecraft’s visible and infrared spectrometer VIR (De Jaumann et al. 2012; Russell et al. 2012). In recent years, several tens of asteroids have been found to show a surface composition similar to that of Vesta and have been clas- E-mail: [email protected]; [email protected] sified as ‘V-types’. Many of these objects belong to the Vesta’s