Martian Meteorite Launch: High-Speed Ejecta from Small Craters

Abstract

We performed high-resolution computer simulations of impacts into homogeneous and layered martian terrain analogs to try to account for the ages and characteristics of the martian meteorite collection found on Earth. We found that craters as small as approximately 3 kilometers can eject approximately 10(7) decimeter-sized fragments from Mars, which is enough to expect those fragments to appear in the terrestrial collection. This minimum crater diameter is at least four times smaller than previous estimates and depends on the physical composition of the target material. Terrain covered by a weak layer such as an impact-generated regolith requires larger, therefore rarer, impacts to eject meteorites. Because older terrain is more likely to be mantled with such material, we estimate that the martian meteorites will be biased toward younger ages, which is consistent with the meteorite collection.

The Tissint Martian meteorite as evidence for the largest impact excavation

“…Therefore, this cratersize estimate, conservatively, might be in error by as much as a factor of 2. Shergottites of similar cosmic-ray exposure (CRE) ages have been regarded to be derived from the same source crater 4 4 . For those with similar CRE ages, it appears to be contradictory to the previous suggestion.…”

“…These high-P phases are typically small (o10 mm) and were only observed in isolated occurrences in or near shock-induced melts within the meteorites (Table 1). Tissint was named for a 2011 meteorite fall in Morocco, near the village of Tissint, and was identified to be a Martian meteorite 4 . Being the freshest Martian sample, this meteorite has generated great interest in the community for the possibility of detecting signs of prior Martian life.…”

Concordant Rb–Sr, Sm–Nd, and Ar–Ar ages for Northwest Africa 1460: A 346Ma old basaltic shergottite related to “lherzolitic” shergottites

“…For comparison, their favored scenario for Martian meteorites is launch from craters >3-7 km in diameter (Head et al, 2002) ''somewhat favoring the larger sizes". This size limit thus approaches the lower limit they consider for large cluster production by ejected blocks >5 m in size.…”

Searching for the source regions of martian meteorites using MGS TES: Integrating martian meteorites into the global distribution of igneous materials on Mars

“…Many studies of cratering dynamics have attempted to describe the dimensions of a crater resulting from an impact capable of ejecting martian materials into an Earth-crossing orbit (Nyquist 1983(Nyquist , 1984Melosh 1985;O'Keefe and Ahrens 1986;Vickery and Melosh 1987;Warren 1994;Gladman 1997;Head 1999;Head and Melosh 2000;Mileikowsky et al 2000;Head et al 2002). Early work indicated that favored candidate craters would be ~100-200 km in diameter and/or that oblique impacts might be required to eject materials from Mars' gravity field, but the most recent estimates have revised the minimum size of circular craters tõ 3 km.…”