Investigations into an unknown organism on the martian meteorite Allan Hills 84001

Examination of fracture surfaces near the fusion crust of the martian meteo rite Allan Hills (ALH) 84001 have been conducted using scanning electron mi croscopy (SEM) and atomic force microscopy (AFM) and has revealed structure s strongly resembling mycelium. These structures were compared with similar structures found in Antarctic cryptoendolithic communities. On morphology alone, we conclude that these features are not only terrestrial in origin b ut probably belong to a member of the Actinomycetales, which we consider wa s introduced during the Antarctic residency of this meteorite. If true, thi s is the first documented account of terrestrial microbial activity within a meteorite from the Antarctic blue ice fields. These structures, however, do not bear any resemblance to those postulated to be martian biota, althou gh they are a probable source of the organic contaminants previously report ed in this meteorite.