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Astron. Astrophys. 335, 351-362 (1998)

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Orbital evolution of asteroidal fragments into the [FORMULA]6 resonance via Yarkovsky effects

D. Vokrouhlický 1 and P. Farinella 2

1 Institute of Astronomy, Charles University, V Holeovikách 2, CZ-180 00 Prague 8, Czech Republic (e-mail: vokrouhl@mbox.cesnet.cz)
2 Gruppo di Meccanica Spaziale, Dipartimento di Matematica, Università di Pisa, Via Buonarroti 2, I-56127 Pisa, Italy (e-mail: paolof@dm.unipi.it)

Received 28 September 1997 / Accepted 24 February 1998


We analyze the dynamical evolution of asteroidal fragments released in the Flora region, near the inner edge of the main asteroid belt, and drifting into the [FORMULA] secular resonance due to Yarkovsky non-gravitational effects. We find that fragments 5 to 20 m in size evolve under the "seasonal" Yarkovsky effect which causes a secular semimajor axis decay; they reach [FORMULA] after a time shorter than their collisional lifetime when they start within about 0.05 to 0.2 AU out of the resonance. Metal-rich fragments drift slower but have have much longer lifetimes than stony ones, so they drift farther from their formation site and sample a wider portion of the inner belt. Fragments around 100 m in size are mainly influenced by the "diurnal" Yarkovsky effect if their surface is covered by a (thin) regolith layer; this causes a random walk in semimajor axis controlled by impacts which reorient the spin axis. Within their lifetime of [FORMULA] Myr these fragments can move throughout the inner part of the asteroid belt, episodically crossing [FORMULA]. Meter-sized stony fragments, which probably deliver most meteorite falls, may also drift into the resonance under the "diurnal" effect, provided their surfaces have low thermal conductivities and/or their rotation is unusually slow. According to our dynamical model, which is truncated to 15 degree in the fragment's orbital eccentricity, [FORMULA] resonance effects typically result into large eccentricity increases, such that main-belt orbits rapidly become Earth-crossing when the resonance is reached and/or crossed. This confirms the idea that the interplay of resonant dynamics and Yarkovsky-related semimajor axis mobility is crucial in the transport of meteorites and small near-Earth asteroids from the main asteroid belt to the near-Earth space.

Key words: celestial mechanics, stellar dynamics – minor planets, asteroids – meteors, meteoroids

Send offprint requests to: D. Vokrouhlický

© European Southern Observatory (ESO) 1998

Online publication: June 12, 1998