Searching for the Source Crater of Nakhlite Meteorites.

We surveyed the Martian surface in order to identify possible source craters of the nakhlite Martian meteorites. We investigated rayed craters that are assumed to be younger than 11 Ma, on lava surfaces with a solidification age around 1.2 Ga. An area of 17.3 million km2 Amazonian lava plains was surveyed and 53 rayed craters were identified. Although most of them are smaller than the threshold limit that is estimated as minimum of launching fragments to possible Earth crossing trajectories, their observed size frequency distribution agrees with the expected areal density from cratering models characteristic for craters that are less than few tens of Ma old. We identified 6 craters larger than 3 km diameter constituting the potentially best source craters for nakhlites. These larger candidates are located mostly on a smooth lava surface, and in some cases, on the earlier fluvial-like channels. In three cases they are associated with fluidized ejecta lobes and rays - although the rays are faint in these craters, thus might be older than the other craters with more obvious rays. More work is therefore required to accurately estimate ages based on ray system for this purpose. A more detailed search should further link remote sensing Martian data with the in-situ laboratory analyses of Martian meteorites, especially in case of high altitude, steep terrains, where the crater rays seems to rarely survive several Ma.