Destination: Earth. Martian meteorite delivery

The delivery dynamics of martian meteorites are examined by means of a direct numerical simulation of their orbital evolution. The dynamics in the martian region are dominated by secular resonant effects, not by close encounters with Mars, These secular effects rapidly (similar to 1 Myr) transport martian ejecta to Earth-crossing orbits. The measured cosmic-ray exposure ages of the martian meteorites are consistent with their being directly launched as small bodies from the martian surface by impacts over the last similar or equal to 15 Myr, Collisional effects and being driven into the Sun efficiently destroy martian meteoroids in space on time scales of order 10 Myr, The implications of these results for the launch mechanism and microorganism transport are discussed. (C) 1997 Academic Press.