Mars has four known co-orbital asteroids ( 5261 Eureka , , all at the Lagrangian point s ) , and Jupiter has many ( an estimated one million greater than 1 km in diameter , the Jovian trojans ) ; there are also other small co-orbital moons in the Saturnian system : Telesto and Calypso with Tethys , and Helene and Polydeuces with Dione .