A PRELIMINARY-ANALYSIS OF THE ORBIT OF THE MARS TROJAN ASTEROID (5261) EUREKA

Observations and results of orbit determination of the first Known Mar s Trojan asteroid (5261) Eureka are presented. We have numerically cal culated the evolution of the orbital elements, and have analyzed the b ehavior of the motion during the next 2 Myr. Strong perturbations by p lanets other than Mars seem to stabilize the eccentricity of the aster oid by stirring the high order resonances present in the elliptic rest ricted problem. As a result, the orbit appears stable at least on mega year timescales. The difference of the mean longitudes of Mars and Eur eka and the semimajor axis of the asteroid form a pair of variables th at essentially behave in an adiabatic manner, while the evolution of t he other orbital elements is largely determined by the perturbations d ue to other planets.