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Dynamics and origin of asteroid families


Among the largest objects in the main belt, asteroid 4 Vesta is unique in showing a basaltic crust. It is also the biggest member of the Vesta family, which is supposed to originate from a large cratering event about I Gyr ago (Marzari et al. 1996). Most of the members of the Vesta family for which a spectral classification is available show a V-type spectra. Due to their characteristic infrared spectrum, V-type asteroids are easily distinguished. Before the discovery of 1459 Magnya (Lazzaro et al. 2000) and of several V-type NEA (Xu 1995), all the known V-type asteroids were members of the Vesta family. Recently two V-type asteroids, 809 Lundia and 956 Elisa, (Florczak et al. 2002) have been discovered well outside the limits of the family, near the Flora family. We currently know 22 V-type asteroids outside the family, in the inner asteroid belt (see Table 2 in Carruba et al. 2005). In Carruba et al. 2005 we investigated the possibility that these objects are former family members that migrated to their current positions via the interplay of Yarkovsky effect and nonlinear secular resonances. In a second article we investigated the role that other mechanisms of dynamical mobility, such as close encounters with massive asteroids, may have played in causing the current orbital distribution of some of the remaining 20 other V-type asteroids. In that work we developed a) a new integrator that account for both the Yarkovsky effect and close encounters with 4 Vesta; b) a new method, based on the Probability Diffusion Function (pdf) of Bachelier 1900 to extrapolate the results of our numerical simulations, and c) study the role that nonlinear secular resonances involving martian frequencies may have played in diffusing former members of the Vesta family. Our results suggests that at least six of the V-type asteroids outside the Vesta family (2442 Corbett, 2640 Hallstrom, 2795 Lepage, 4188 Kitezh, 4434 Nikulin, and 4977 Lewis) can be explained in the framework of close encounters with the family parent body. Our work on close encounters of family members with 4 Vesta has answered some questions, but left several others unanswered. Among them, the most important is to understand how the pdf varies as a function of the location in proper element space of the scattered asteroids, and how this new method may be applied to other asteroid families perturbed by massive asteroids. Another interesting question our work left unanswered is the relevance of the YORP effect when asteroid diffusion is considered. Our second article has shown what interesting dynamics can be produced when the Yarkovsky effect is considered in combination with non-linear secular resonances, even weak ones such as the s - s4 + g6 - g5 and s - s4 + g6 - g7 martian secular resonances. A problem left for investigation is to understand what happens when the YORP effect (the torque that modify the rotation rate and the orientation of the asteroids' spin axis, due to the irregularly shaped objects thermal re-emission) is considered, in particular for the 'surfing' orbits we studied in the second article. Finally, as a complementary part of the project, we would like to investigate some details of the dynamics of a few irregular satellites of Jovian planets, with an emphasis on the chaotic orbits of two jovian satellites, Pasiphae and Sinope. (AU)

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Scientific publications (9)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
CARRUBA, V.. The stable archipelago in the region of the Pallas and Hansa dynamical families. Monthly Notices of the Royal Astronomical Society, v. 408, n. 1, p. 580-600, . (06/50005-5)
CARRUBA, V.; MORBIDELLI, A.. On the first nu(6) anti-aligned librating asteroid family of Tina. Monthly Notices of the Royal Astronomical Society, v. 412, n. 3, p. 2040-2051, . (06/50005-5)
CARRUBA, V.; MACHUCA, J. F.; GASPARINO, H. P.. Dynamical erosion of asteroid groups in the region of the Pallas family. Monthly Notices of the Royal Astronomical Society, v. 412, n. 3, p. 2052-2062, . (06/50005-5)
CARRUBA, V.. The (not so) peculiar case of the Padua family. Monthly Notices of the Royal Astronomical Society, v. 395, n. 1, p. 358-377, . (06/50005-5)
CARRUBA, V.. An analysis of the region of the Phocaea dynamical family. Monthly Notices of the Royal Astronomical Society, v. 398, n. 3, p. 1512-1526, . (06/50005-5)
CARRUBA‚ V.; ROIG‚ F.; MICHTCHENKO‚ TA; FERRAZ-MELLO‚ S.; NESVORNỲ‚ D.. Modeling close encounters with massive asteroids: a Markovian approach. Astronomy & Astrophysics, v. 465, n. 1, p. 315-330, . (06/50005-5)
MACHUCA, J. F.; CARRUBA, V.. Secular dynamics and family identification among highly inclined asteroids in the Euphrosyne region. Monthly Notices of the Royal Astronomical Society, v. 420, n. 2, p. 1779-1798, . (06/50005-5)
CARRUBA, V.; MACHUCA, J. F.. On the Emmenthal distribution of highly inclined asteroids. Monthly Notices of the Royal Astronomical Society, v. 418, n. 2, p. 1102-1114, . (06/50005-5)

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