Atmosphere - crust coupling and carbon sequestration on early Mars

[摘要] Evidence exists for great volumes of water on early Mars. Liquid surface water requires a much denser atmosphere than modern Mars possesses, probably predominantly composed of CO2. Such significant volumes of CO2 and water in the presence of basalt should have produced vast concentrations of carbonate minerals, yet little carbonate has been discovered thus far. These ‘missing carbonates’ comprise the Mars carbonate conundrum. This thesis provides insight to the conundrum via three distinct lines of investigation. Firstly, using engineering to expand our ability to locate carbonates on the Martian surface. A Micro-Optic UltraSonic Exfoliator (MOUSE) was designed and built that was tested on a range of rock types and wavelengths. Using ultrasonics demonstrates many advantages over the rock abrasion tool currently used on Mars rovers, including a smoother grind finish and a lower rate of tool tip wear when using tungsten carbide. Secondly, carbonates present in our only samples of the Martian regolith on Earth, meteorites, were studied. Carbonates found in Martian meteorites can provide a record of aqueous and atmospheric conditions extending back over 4.5 billion years. This thesis observes carbonates in two meteorites, ALH 84001 and Lafayette, representing early Mars and more recent Mars respectively, and finds evidence for two types of carbonate replacing glass in ALH 84001. The aqueously altered minerals of these two meteorites were compared with those found in the terrestrial ophiolites of Leka (Norway), and Semail (United Arab Emirates), and these ophiolites were assessed for suitability as Mars analogues. Chemically zoned carbonate rosettes similar to those in ALH 84001 are found in the Semail ophiolite samples. No carbonates were identified in Leka samples, but extensive serpentinisation was present. Finally, this thesis sought to replicate alteration processes and products that are recorded by Martian meteorites within a Mars analogue laboratory environment. The effects of differing initial atmospheric and mineral compositions were explored, specifically the comparison of CO2 and SO2 with basalt versus CO2 with olivine.These three interdisciplinary strands of investigation provide some novel tools, ideas and evidence to help solve the Mars carbonate conundrum.

[发布机构] University:University of Glasgow;Department:School of Geographical and Earth Sciences

[关键词] Mars, carbon, CCS, atmosphere, sequestration, carbonate, climate, crust, rover.