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Title: Seismic exploration of Mars and the NASA InSight Mission
Author: Taylor , Jennifer
ISNI:       0000 0000 6470 1704
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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Comparative planetology is a growing discipline, and one which seeks to fundamentally address and improve our understanding of the Earth in the context of wider solar system processes. Missions to the other terrestrial planets vastly increase the data available for observation of contrasting planetary processes, and the upcoming 2016 NASA InSight mission to Mars is of particular importance. In recent years, exploration missions have focused primarily on surface imaging or geochemistry; InSight aims to penetrate deeper into Mars to observe what is happening at depth. To do this, it will use seismic energy to image and map the interior. Amongst other geophysical payload instruments, it will deploy two three-component seismometers (one short period and one broadband sensor) on to the Martian surface atop a tripod. In this thesis, I address the primary InSight team science goals by characterising and quantifying potential sources of seismic and acoustic energy that may provide signal to map the interior of Mars. In the first science chapter, I explore the potential of tectonic sources for InSight by analysing a series of faults known as the Cerberus Fossae on the Elysium Planitia of Mars. I found that these graben have the best evidence on Mars for current and on-going tectonic activity. Combining topographic data with crater count statistics to date the faults allowed me to calculate a size frequency distribution of events. By then taking into account the InSight instrument capabilities and the environmental noise estimates for Mars, I calculate there to be between 1.5 x 100 and 1.9 x 105 detectable tectonic events per year from the Cerberus Fossae. The implication of this number of events for InSight is important, since it compares to previous estimates of global tectonic activity. Events at the source-receiver distance of the Cerberus Fossae to the InSight landing site may also penetrate deep into Mars, sampling the structure of the mantle and potentially the core-mantle boundary. The second science chapter focuses on meteor airbursts as a potential seismo-acoustic source for InSight. By combining terrestrial analogue data with modelling of bolide properties, I was able to define a catalogue of diagnostic properties to identify an airburst, determine novel ways to utilise frequency content of the signal to determine parameters such as source-receiver distance and explosion yield, as well as estimate a number of detectable events per year for InSight. Here I predict between zero and 8.13 ± 1.68 x 106 , depending on the bolide material and strength parameters. This number is also significant for InSight, since it will allow NASA to address its science goal to observe and characterise the Martian impactor population. Smaller meteors are more likely to impact the top of the Martian atmosphere because of the size-frequency distribution of the source population. However these smaller bodies are also more likely to fragment. The ability to recognise airbursts will vastly improve the statistics of the observation of the Mars impactor population. The final science chapter concerns the deployment of the InSight seismometers and explores how the deployment configuration may affect the recording of signal from external seismic sources. I carry out a series of experiments in an analogue field environment designed to test how the seismometer mounting tripod mass and leg con'figuration affect the coupling of the signal from the regolith to the sensor. I find that the tripod transfer function does influence the signal recorded by the sensors. The resonance of the tripod platform imparts energy at spurious frequencies within the frequency range of interest for InSight. This effect will need to be taken into consideration and removed before the real InSight data is analysed. InSight will greatly increase our understanding of how Mars and the solar system evolved. By predicting and characterising signal inputs and highlighting potential problems, I hope to contribute to the analysis and understanding of the real InSight data when it is returned form Mars in 2016.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available