The Martian meteorite paradox: Climatic influence on impact ejection from Mars?

The large number of Martian meteorites with “young” crystallization ages (especially shergottites formed ∼ 170 Myr ago on Mars) represents a paradox, because it suggests that either the mean surface age of Mars is rather young or that specific source regions are preferentially amenable for impact sampling. We present a climate controlled scenario, in which surface regions of limited extent have been especially favored for impact ejection of Martian meteorites during the past ∼ 5 Myr. This conclusion implies that the ejection ages of the shergottites may be used to constrain the end of the last major glaciations on Mars.