An Investigation into Shock Events on Martian Analogue Minerals using Raman Spectroscopy

In early 2021 both NASA's Mars 2020 and ESA's Rosalind Franklin rovers will land on Mars carrying Raman spectrometers. This will be the first time that a Raman spectrometer has been deployed on another planetary body and both rovers will conduct their mission in regions that contain impact craters and, therefore, it is likely that both missions will encounter samples that have been subjected to shock. This thesis examines how the Martian environment can potentially influence the Raman spectrum of minerals, which was achieved by examining the effects of temperature and shock. The first series of experiments investigated the influence of temperature on the Raman spectrum of the three minerals: olivine, quartz, and labradorite. These experiments showed that the Raman peak positions vary based on the temperature of the sample. As the sample temperature was increased, the Raman peak position decreased (at varying rates) for all three minerals, which could lead to the misinterpretation of the exact composition of the minerals samples if not properly corrected for. Further temperature investigations were also conducted into the degree of 'laser heating' generated in samples by the Raman spectrometer during acquisition. Mineral samples with a range of grain sizes were tested to determine if there is a relationship between the size of the sample and the amount of 'laser heating'. This experiment was not able to detect the presence of any 'laser heating' in any of the samples, however, an experimental procedure has now been developed and can be repeated with smaller, more appropriately sized grains in the future. The second series of experiments explored the effects of shock on the Raman spectrum of the same three minerals. For this experiment, each of the minerals was impacted using the light gas gun at the University of Kent at a range of velocities (and therefore shock pressures) before being examined using a Raman spectrometer. An attempt was made to determine if the induced changes in the Raman spectrum of the samples could be used as a shock barometer to infer the magnitude of shock experienced by the sample. Results showed that this was generally not possible as much of the shocked material had been excavated during the crater formation process. It was found that lower speed shots, which merely produced an indentation on the surface of the samples without the loss of material, were better suited to such an investigation. As such, methods of firing the light gas gun at a lower velocity were used. This was done to preserve the experimental procedure across all velocities in order to reduce the chance of introducing systematic errors to the dataset. This required the development of an entirely new firing system known as the electronic burst disk which is presented here in full for the first time

Observations of impacted, frozen Lunar and Martian regolith simulants

An examination of impact flashes from frozen Lunar and Martian simulant (JSC-1A and JSC-1 respectively) was carried out in order to better understand the physical and chemical behaviour of the highly energetic, short-lived, ejecta cloud. The relative emission intensity and decay from the impact ejecta were examined across 10 spectral regions and a semi-quantitative analysis of the peak flash intensity and relative densities of the frozen targets carried out. Additional experiments recorded the emission spectra of the frozen target ejecta during the first 15 microseconds after impact to more clearly understand the origin of any atomic/molecular emission

Variability in IC5070: two young stars with deep recurring eclipses

Investigating the structure and properties of the innermost parts of protoplanetary accretion disks on sub-AU scales is currently only possible via indirect methods. One option to map the planet-forming zone is to search for occultations of the central young stellar object (YSO) by circumstellar material, e.g., warps or clumps in the inner disks. Such disk eclipses typically last hours to days (Cody et al. 2014) and have been identified in massive HAeBe stars such as UX Ori (Herbst & Shevchenko 1999) and lower mass objects such as AA Tau (Bouvier et al. 1999). Of particular interest are quasi-periodic dimming events. They allow distance determinations of the occulting material from the central star. In such cases the actual azimuthal physical extent of the material can be determined from the duration of the dimming event relative to the period. Observations over several periods enable investigations into temporal changes in the line of sight column density distribution, and multi-wavelength data allows us to probe the dust scattering properties. Our citizen science project HOYS-CAPS (Froebrich et al. 2018) aims to identify such periodic dimming events around YSOs. We used this data-set to search for periodic signatures in light-curves from YSOs in the Pelican nebula (IC 5070). For this field we have ~200 individual observations in the V, R, and I-band filters, distributed over ~800 days. Hence, the average cadence is 4 days, but the most frequent gap (30%) between subsequent observations is 2 days. Observations are usually taken as 8 × 2 minutes integrations in all filters to achieve a consistent S/N