Production and escape of Trojan asteroids by non-gravitational forces at 1.5 au from the Sun

Abstract

We provide a quantitative explanation for the peculiar orbital distribution of Mars Trojans, with three similar-sized asteroids and a family of smaller Trojans associated with only one of those, (5261) Eureka, as the balance between different rates of production and loss of new asteroids by solar-radiation-driven forces. In one case, a slow rotation has effectively shut off new asteroid production by YORP-induced rotational fission. In another, new asteroids are driven by the Yarkovsky effect to quickly escape from the Trojan clouds. Out of the three objects, Eureka is the only case where new asteroids may be efficiently produced and retained for a good fraction of the solar system's age, explaining the Eureka family. Our model will be tested by ongoing (PanSTARRS, GAIA) and future (LSST) asteroid surveys that will allow us to search for much smaller Trojans and to identify new clusters, if they exist. This work highlights the Martian Trojans as a natural laboratory to study the action of non-gravitational forces at 1.5 au from the Sun.