Trojan asteroids and the co-orbital dust ring of Venus

Context. Co-orbital asteroids have been thought to be the possible source of the zodiacal dust ring around the orbit of Venus, but the conclusions about the orbital stability and thus about the existence of Venus Trojans are inconsistent in the literature. Aims. We present a systematic survey of the orbital stability of Venus Trojans that takes the dynamical influences from General Relativity and the Yarkovsky effect into account. Methods. The orbits of thousands of fictitious Venus Trojans were simulated numerically. Using a frequency analysis, we describe their orbital stabilities and the dynamical mechanisms behind them. The influences of General Relativity and of the Yarkovsky effect, which were previously either neglected or oversimplified, were investigated in long-term numerical simulations. Results. The stability maps on the ( a 0 , i 0 ) plane and ( a 0 , e 0 ) plane are depicted, and the most stable Venus Trojans are found to occupy low-inclination horseshoe orbits with low eccentricities. The resonances that carve the fine structures in the stability map are determined. General Relativity decreases the stability of orbits only little, but the Yarkovsky effect may drive nearly all Venus Trojans out of the Trojan region in a relatively short time. Conclusions. The Venus Trojans have a poor orbital stability and cannot survive to the age of the Solar System. The zodiacal dust ring found around the orbit of Venus is more likely a sporadic phenomenon, as the result of a temporary capture into the 1:1 mean motion resonance of dust particles that were probably produced by passing comets or asteroids, but not by Venus Trojans.