In Situ Analysis of Opal in Gale Crater, Mars

Silica enrichments resulting in up to ~90 wt% SiO2 have been observed by the Curiosity rover's instruments in Gale crater, Mars, within the Murray and Stimson formations. Samples acquired by the rover drill revealed a significant abundance of an X‐ray amorphous silica phase. Laser‐induced breakdown spectroscopy (LIBS) highlights an overall correlation of the hydrogen signal with silica content for these Si‐enriched targets. The increased hydration of the high‐silica rocks compared to the surrounding bedrock is also confirmed by active neutron spectroscopy. Laboratory LIBS experiments have been performed to calibrate the hydrogen signal and show that the correlation observed on Mars is consistent with a silica phase containing on average 6.3 ± 1.4 wt% water. X‐ray diffraction and LIBS measurements indicate that opal‐A, amorphous hydrated silica, is the most likely phase containing this water in the rocks. Pyrolysis experiments were also performed on drilled samples by the Sample Analysis at Mars (SAM) instrument to measure volatile content, but the data suggests that most of the water was released during handling prior to pyrolysis. The inferred low‐temperature release of water helps constrain the nature of the opal. Given the geological context and the spatial association with other phases such as calcium sulfates, the opal was likely formed from multiple diagenetic fluid events and possibly represents the latest significant water‐rock interaction in these sedimentary rocks

Firing the climate canon: a literary critique of the genre of climate change

This article makes the case for more climate change, where climate change refers to the prevailing ideologies and frameworks that inform our understanding of environmental change in the first place. It reviews the mainstream literature in popular science writing, fiction and poetry from the point of view of a political frame analysis of climate change, to demonstrate how a certain understanding of climate change maps onto conventions of literary genre. This understanding, and associated literature, are critiqued on the basis of their continued attachment to dualistic and teleological narratives of human mastery and progress, such as to make the case for a literature which offers something radically other. The current political context, not least Donald Trump’s victory and Brexit, are cited as evidence of the contemporary importance of alternatives to the establishment approach to climate mitigation than either denial or scepticism – in both literature, and more broadly

Peisleyite an Unusual Mixed Anion Mineral - A Vibrational Spectroscopic Study

The mineral peisleyite has been studied using a combination of electron microscopy and vibrational spectroscopy. SEM photomicrographs reveal that the peisleyite morphology consists of an array of small needle like crystals of around 1 μm in length with a thickness of less than 0.1 μm. Raman spectroscopy in the hydroxyl stretching region shows an intense band at 3506 cm-1 assigned to the symmetric stretching mode of the OH units. Four bands are observed at 3564, 3404, 3250 and 3135 cm-1 in the infrared spectrum. These wavenumbers enable an estimation of the hydrogen bond distances 3.052(5), 2.801(0), 2.705(6) and 2.683(6) Å. Two intense Raman bands are observed at 1023 and 989 cm-1 and are assigned to the SO4 and PO4 symmetric stretching modes. Other bands are observed at 1356, 1252, 1235, 1152, 1128, 1098 and 1067 cm-1. The bands at 1067 is attributed to AlOH deformation vibrations. Bands in the low wavenumber region are assigned to the ν4 and ν2 out of plane bending modes of the SO4 and PO4 units. Raman spectroscopy is a useful tool in determining the vibrational spectroscopy of mixed hydrated multianion minerals such as peisleyite. Information on such a mineral would be difficult to obtain by other means

Raman Spectroscopy of Phosphates of the Variscite Mineral Group

Raman spectra of phosphates of the variscite mineral group, namely strengite, variscite, metavariscite and phosphosiderite, were obtained at 298 and 77 K using a thermal stage and complemented with selected infrared data using a diamond attenuated total reflection cell. Multiple phosphate stretching bands are observed. Bands for strengite at 1006, 1012 and 1026 cm-1 at 298 K and at 997, 1006, 1014 and 1027 cm-1 at 77 K are observed. Variscite is characterized by PO stretching vibrations at 1023, 1005 and 938 cm-1 and phosphosiderite by bands at 1009 and 993 cm-1. These minerals are readily identified by their Raman spectrum both in the PO stretching region and in the low-wavenumber region. Multiple bands attributed to the bending modes of PO4 are identified for each of the minerals. A model is proposed involving non-hydrogen-bonded PO4 and strongly hydrogen-bonded PO4 units together with [Al or Fe(OH)2]+ ·(H2PO4)2--type species. Raman spectroscopy shows that at the molecular level multiple species of phosphate anions exist for the variscite phosphate minerals

Contributions to pure and applied mineralogy / E.R. Segnit

1 v.Title page, contents and abstract only. The complete thesis in print form is available from the University Library.Thesis -- University of Adelaide, 198