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D. Lazzaro (MCT/ON), T. Michtchenko (IAG/USP), T.A. Gumarães (MCT/ON), C.A. Angeli (MCT/ON)
Asteroid 4 Vesta has been known as the unique object of the main belt showing a basaltic crust. Its composition is also similar to that of basaltic achondrite meteorites (HED). However, while the global surface composition of 4 Vesta is very similar to that of HED, the estimated times needed to transport fragments from 4 Vesta to Earth seem to be too rapid to be compatible with the cosmic ray exposure time observed in HED. The recent discovery [Lazzaro et al., Science 288, 2000] of a small basaltic asteroid, 1459 Magnya in the outer asteroid belt opens an alternative possibility for the source of the V-type NEAs and the HED.
To test this hypothesis, the region around 1459 Magnya has been mineralogically examined searching for other possible "remnants". We analyzed all the asteroids from this region with known composition (or taxonomy) and observed several others. The observations were made with the 1.52m telescope at the ESO (La Silla, Chile) giving a useful spectrum range of 4990-9200A. Up to now, no other basaltic or olivine-rich asteroid has been found. This result may be attributed to our observational limitation to big asteroids. On the other hand, there are, at least, three asteroids with an inferred composition similar to M-type which could be from the nucleus of Magnya's parent body.
Assuming that the majority of fragments of the break-up event were spread from this region, we investigated possible dynamical mechanisms and routes which could transport fragments to NEAs orbits. The region around 1459 Magnya is found to be densely filled by mean-motion resonances that induce slow
diffusion of asteroids from this region. In particular, the orbital eccentricity of an asteroid can pumped-up to until it becomes Mars-crosser. The diffusion times needed are also discussed.