Constraining the formation conditions of the ancient martian ALH 84001 carbonates

The martian meteorite ALH 84001 contains carbonates that provide information about the past aqueous conditions on Mars 3.9 Ga, and have been suggested to display signatures of martian organics. Determining the conditions under which the carbonates formed is crucial for addressing whether there was once life on Mars and the history of martian hydrosphere and atmosphere. This study has combined new sample preparation techniques with fresh isotopic analyses of ALH 84001 carbonates and analogue materials, geochemicai modelling and the testing of future equipment (WatSen) suitable for carbonate detection on Mars. The results from these lnvestigations have provided quantitative constraints on the formation environment for the ALH 84001 carbonates and an instrument capable of detecting carbonates on Mars. The microscale carbon and oxygen analyses of ALH 84001 carbonates provide the first combined transient study across the carbonates with δ13C and δ l80 values correlated ,with chemical compositions. The δ 13C values range from -18.6%0 to +23.2%0 extending and ,.lowering the previous ion microprobe δ 13C range found and suggests that reduced carbon is present in the carbonates. This component exists as either macromolecular carbon introduced through sub sequent alteration, terrestrial contamination or martian organics. The δ l80 range - ~;•l +27. 1%0 is consistent with previous authors and displays a clear correlation with δ l80 enrichment with distance from the carbonates core to edge. An 18.6%0 range in δ l80 values was measured across analogue carbonates similar in size, shape and chemical variation which formed in a hydrothermal environment.EThOS - Electronic Theses Online ServiceGBUnited Kingdo