 Since olivine-rich objects are rare in the asteroid belt it has been suggested that some of the Mars trojans are captured debris from a large orbit-altering impact on Mars when it encountered a planetary embryo.Presently, this group contains seven asteroids confirmed to be stable Mars trojans by long-term numerical simulations but only four of them are accepted by the Minor Planet Center (†) and there is one candidate.Due to close orbital similarities, most of the smaller members of the L5 group are hypothesized to be fragments of Eureka that were detached after it was spun up by the YORP effect (Eureka's rotational period is 2.69 h).