Spectroscopic Study of Habitable Environments on Mars

In the recent decades, surface and orbital missions to Mars have developed our understanding of the planet’s geological and environmental history. We now have strong evidence that Mars supported habitable environments in the Noachian and early Hesperian Periods. Much of this information has been developed using spectroscopic techniques; modern surface missions to Mars commonly feature a range of passive and active spectrometers among their instrument suites, and orbital satellites also use reflectance spectroscopy to determine compositions of observed terrain.

This thesis covers analysis of spectroscopic data from the Mars Science Laboratory mission, in particular the ChemCam laser induced breakdown spectrometer on board the Curiosity rover. In addition, data is presented from a terrestrial Mars analogue study using Raman spectroscopy; Raman spectroscopy has newly been deployed on Mars by the Mars 2020 mission and will be used by the upcoming ExoMars Rosalind Franklin rover to continue the search for signs of life on Mars.

Data from the Curiosity rover is used to analyse the Askival float sample. This sample has characteristic textures of a feldspar cumulate rock but has been significantly altered to the point where the feldspar phase has been heavily replaced by opaline silica. This alteration was likely the result of exposure to low-temperature fluids of changing pH. Askival’s origin as a feldspathic cumulate may be representative of buried felsic material in the surrounding crater rim.

I also examine ChemCam data from the Glen Torridon region of Gale crater. This region is notable for the confirmation of carbonate minerals by the CheMin mineralogy instrument. ChemCam data indicates that the CheMin drilled samples are geochemically representative of the broader bedrock and therefore the carbonate is likely to be widespread throughout the region and not associated with isolated diagenetic alteration. The Glen Torridon sediments record a sabkha environment with periodic flooding and evaporation. Later acidic alteration may be responsible for removing carbonate, leading to the observed “patchy” distribution.

Raman spectroscopy results are presented on basaltic sediments from Þórisjökull, Iceland, mixed with carbonate and phyllosilicate minerals. Both carbonate and phyllosilicate are resolvable in the Raman spectra below 5% bulk weight. Possible mineralogical misidentifications that present risks to analysis of mixed samples of the type that may be found at the planned Oxia Planum ExoMars landing site are examined in the context of these results.

In combination, this analysis further expand the record of fluid events in Gale crater, whilst demonstrating the ability of Raman spectroscopy to assist in the detection of mineral evidence for fluid alteration and diagenesis.