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- All Subjects: Mars
- Creators: Sharp, Thomas
Description
Early spacecraft missions to Mars, including the Marnier and Viking orbiters and landers revealed a morphologically and compositionally diverse landscape that reshaped widely held views of Mars. More recent spacecraft including Mars Global Surveyor, Mars Odyssey, Mars Express, Mars Reconnaissance Orbiter, and the Mars Exploration Rovers have further refined, enhanced, and diversified our understanding of Mars. In this dissertation, I take a multiple-path approach to planetary and Mars science including data analysis and instrument development. First, I present several tools necessary to effectively use new, complex datasets by highlighting unique and innovative data processing techniques that allow for the regional to global scale comparison of multiple datasets. Second, I present three studies that characterize several processes on early Mars, where I identify a regional, compositionally distinct, in situ, stratigraphically significant layer in Ganges and Eos Chasmata that formed early in martian history. This layer represents a unique period in martian history where primitive mantle materials were emplaced over large sections of the martian surface. While I originally characterized this layer as an effusive lava flow, based on the newly identified regional or global extent of this layer, I find the only likely scenario for its emplacement is the ejecta deposit of the Borealis Basin forming impact event. I also re-examine high thermal inertia, flat-floored craters identified in Viking data and conclude they are typically more mafic than the surrounding plains and were likely infilled by primitive volcanic materials during, or shortly after the Late Heavy Bombardment. Furthermore, the only plausible source for these magmas is directly related to the impact process, where mantle decompression melting occurs as result of the removal of overlying material by the impactor. Finally, I developed a new laboratory microscopic emission and reflectance spectrometer designed to help improve the interpretation of current remote sensing or in situ data from planetary bodies. I present the design, implementation, calibration, system performance, and preliminary results of this instrument. This instrument is a strong candidate for the next generation in situ rover instruments designed to definitively assess sample mineralogy and petrology while preserving geologic context.
ContributorsEdwards, Christopher (Author) / Christensen, Philip R. (Thesis advisor) / Bell, James (Committee member) / Sharp, Thomas (Committee member) / Clarke, Amanda B (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2012
Description
Amorphous phases are detected over large regions of the Martian surface from orbit and in more localized deposits by rovers on the surface. Amorphous silicates can be primary or secondary in origin, both having formed through very different processes, so the unambiguous identification of these phases is important for understanding the geologic history of Mars. Secondary amorphous silicates are poorly understood and underrepresented in spectral libraries because they lack the long-range structural order that makes their crystalline counterparts identifiable in most analytical techniques. Fortunately, even amorphous materials have some degree of short-range order so that distinctions can be made with careful characterization.
Two sets of laboratory experiments were used to produce and characterize amorphous weathering products under probable conditions for the Martian surface, and one global spectral analysis using thermal-infrared (TIR) data from the Thermal Emission Spectrometer (TES) instrument was used to constrain variations in amorphous silicates across the Martian surface. The first set of experiments altered crystalline and glassy basalt samples in an open system under strong (pH 1) and moderate (pH 3) acidic conditions. The second set of experiments simulated a current-day Martian weathering scenario involving transient liquid water where basalt glass weathering solutions, formed in circumneutral (pH ~5.5 and 7) conditions, were rapidly evaporated, precipitating amorphous silicates. The samples were characterized using visible and near-infrared (VNIR) spectroscopy, TIR spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD).
All experiments formed amorphous silicate phases that are new to spectral libraries. Moderately acidic alteration experiments produced no visible or spectral evidence of alteration products, whereas exposure of basalt glass to strongly acidic fluids produced silica-rich alteration layers that are spectrally consistent with VNIR and TIR spectra from the circum-polar region of Mars, indicating this region has undergone acidic weathering. Circum-netural pH basalt weathering solution precipitates are consistent with amorphous materials measured by rovers in soil and rock surface samples in Gale and Gusev Craters, suggesting transient water interactions over the last 3 billion years. Global spectral analyses determine that alteration conditions have varied across the Martian surface, and that alteration has been long lasting.
Two sets of laboratory experiments were used to produce and characterize amorphous weathering products under probable conditions for the Martian surface, and one global spectral analysis using thermal-infrared (TIR) data from the Thermal Emission Spectrometer (TES) instrument was used to constrain variations in amorphous silicates across the Martian surface. The first set of experiments altered crystalline and glassy basalt samples in an open system under strong (pH 1) and moderate (pH 3) acidic conditions. The second set of experiments simulated a current-day Martian weathering scenario involving transient liquid water where basalt glass weathering solutions, formed in circumneutral (pH ~5.5 and 7) conditions, were rapidly evaporated, precipitating amorphous silicates. The samples were characterized using visible and near-infrared (VNIR) spectroscopy, TIR spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD).
All experiments formed amorphous silicate phases that are new to spectral libraries. Moderately acidic alteration experiments produced no visible or spectral evidence of alteration products, whereas exposure of basalt glass to strongly acidic fluids produced silica-rich alteration layers that are spectrally consistent with VNIR and TIR spectra from the circum-polar region of Mars, indicating this region has undergone acidic weathering. Circum-netural pH basalt weathering solution precipitates are consistent with amorphous materials measured by rovers in soil and rock surface samples in Gale and Gusev Craters, suggesting transient water interactions over the last 3 billion years. Global spectral analyses determine that alteration conditions have varied across the Martian surface, and that alteration has been long lasting.
ContributorsSmith, Rebecca (Author) / Christensen, Philip R. (Philip Russel) (Thesis advisor) / Shock, Everett (Committee member) / Hartnett, Hilairy (Committee member) / Shim, Sang-Heon (Committee member) / Sharp, Thomas (Committee member) / Arizona State University (Publisher)
Created2016
Description
Identifying space resources is essential to establish an off-Earth human presence on the Moon, Mars, and beyond. One method for determining the composition and mineralogy of planetary surfaces is thermal infrared emission spectroscopy. I investigated this technique as a potential tool to explore for magmatic Ni-Cu±PGE sulfide deposits by producing and measuring a 100% sulfide (pyrrhotite) sample derived from the Stillwater Complex. Pyrrhotite violates key assumptions used to calibrate thermal infrared emission data, making extraterrestrial sulfides “appear colder” than their actual physical temperature, and their spectra will contain a negative slope. To derive the absolute emissivity of graybody minerals more accurately, I developed a new measurement technique, which demonstrates that pyrrhotite is spectrally featureless in the mid-infrared and has a maximum emissivity of ~0.7. Magmatic sulfide deposits are commonly associated with silicates. Thus, emissivity spectra of sulfide/silicate mixtures were acquired to further understand how sulfide prospecting would be conducted on rocky bodies such as Mars. I demonstrate that as sulfide increases, the apparent brightness temperature decreases linearly and, if left unaccounted for, will contribute a negative spectral slope in their emissivity spectra. The presence of sulfide also reduces the magnitude of all the silicate’s diagnostic spectral features, which is linear as sulfide increases. A linear retrieval algorithm was also applied to the mixture spectra, demonstrating that sulfide could be detected at abundances of ≥10 modal %.
The main resource being targeted for mining on the Moon is water ice. Thus, a mining map tool of the Lunar South Pole that incorporates temperature, illumination, Earth visibility, and slope data was developed to identify the most suitable locations for water ice mining and establishing bases for operations. The map is also used to assess the mining potential of the Artemis III candidate landing regions. Finally, space mining must be governed, but no framework has yet to be established. I propose a governance structure, notification system, contract system, best mining practices, and area-based environmental regulations to manage water ice mining activities. The Lunar Mining Map Tool’s block system is used as a spatial planning tool to administer the governance framework and facilitate management.
ContributorsHubbard, Kevin M (Author) / Elkins-Tanton, Linda T (Thesis advisor) / Christensen, Philip R (Committee member) / Semken, Steven (Committee member) / Sharp, Thomas (Committee member) / O'Rourke, Joseph G (Committee member) / De Zwart, Melissa (Committee member) / Arizona State University (Publisher)
Created2023
Description
Part I – I analyze a database of Smoothed Particle Hydrodynamics (SPH) simulations of collisions between planetary bodies and use the data to define semi-empirical models that reproduce remant masses. These models may be leveraged when detailed, time-dependent aspects of the collision are not paramount, but analytical intuition or a rapid solution is required, e.g. in ‘N-body simulations’. I find that the stratification of the planet is a non-negligible control on accretion efficiency. I also show that the absolute scale (total mass) of the collision may affect the accretion efficiency, with larger bodies more efficiently disrupting, as a function of gravitational binding energy. This is potentially due to impact velocities above the sound speed. The interplay of these dependencies implies that planet formation, depending on the dynamical environment, may be separated into stages marked by differentiation and the growth of planets more massive than the Moon.
Part II – I examine time-resolved neutron data from the Dynamic Albedo of Neutrons (DAN) instrument on the Mars Science Laboratory (MSL) Curiosity rover. I personally and independently developed a data analysis routine (described in the supplementary material in Chapter 2) that utilizes spectra from Monte Carlo N-Particle Transport models of the experiment and the Markov-chain Monte Carlo method to estimate bulk soil/rock properties. The method also identifies cross-correlation and degeneracies. I use data from two measurement campaigns that I targeted during remote operations at ASU. I find that alteration zones of a sandstone unit in Gale crater are markedly elevated in H content from the parent rock, consistent with the presence of amorphous silica. I posit that these deposits were formed by the most recent aqueous alteration events in the crater, since subsequent events would have produced matured forms of silica that were not observed. I also find that active dunes in Gale crater contain minimal water and I developed a Monte Carlo phase analysis routine to understand the amorphous materials in the dunes.
Part II – I examine time-resolved neutron data from the Dynamic Albedo of Neutrons (DAN) instrument on the Mars Science Laboratory (MSL) Curiosity rover. I personally and independently developed a data analysis routine (described in the supplementary material in Chapter 2) that utilizes spectra from Monte Carlo N-Particle Transport models of the experiment and the Markov-chain Monte Carlo method to estimate bulk soil/rock properties. The method also identifies cross-correlation and degeneracies. I use data from two measurement campaigns that I targeted during remote operations at ASU. I find that alteration zones of a sandstone unit in Gale crater are markedly elevated in H content from the parent rock, consistent with the presence of amorphous silica. I posit that these deposits were formed by the most recent aqueous alteration events in the crater, since subsequent events would have produced matured forms of silica that were not observed. I also find that active dunes in Gale crater contain minimal water and I developed a Monte Carlo phase analysis routine to understand the amorphous materials in the dunes.
ContributorsGabriel, Travis Saint James (Author) / Asphaug, Erik I (Thesis advisor) / Hardgrove, Craig (Thesis advisor) / Sharp, Thomas (Committee member) / Zolotov, Mikhail (Committee member) / Young, Patrick (Committee member) / Arizona State University (Publisher)
Created2019
Description
Lava flow emplacement in the laboratory and on the surface of Mars was investigated. In the laboratory, the effects of unsteady effusion rates at the vent on four modes of emplacement common to lava flow propagation: resurfacing, marginal breakouts, inflation, and lava tubes was addressed. A total of 222 experiments were conducted using a programmable pump to inject dyed PEG wax into a chilled bath (~ 0° C) in tanks with a roughened base at slopes of 0, 7, 16, and 29°. The experiments were divided into four conditions, which featured increasing or decreasing eruption rates for either 10 or 50 s. The primary controls on modes of emplacement were crust formation, variability in the eruption rate, and duration of the pulsatory flow rate. Resurfacing – although a relatively minor process – is inhibited by an extensive, coherent crust. Inflation requires a competent, flexible crust. Tube formation requires a crust and intermediate to low effusion rates. On Mars, laboratory analogue experiments combined with models that use flow dimensions to estimate emplacement conditions and using high resolution image data and digital terrain models (e.g. THEMIS IR, CTX, HRSC), the eruption rates, viscosities, and yield strengths of 40 lava flows in the Tharsis Volcanic Province have been quantified. These lava flows have lengths, mean widths, and mean thicknesses of 15 – 314 km, 0.5 – 29 km, and 11 – 91 m, respectively. Flow volumes range from ~1 – 430 km3. Based on laboratory experiments, the 40 observed lava flows were erupted at 0.2 – 6.5x103 m3/s, while the Graetz number and Jeffrey’s equation when applied to 34 of 40 lava flows indicates eruption rates and viscosities of 300 – ~3.5 x 104 m3/s and ~105 – 108 Pa s, respectively. Another model which accounts for mass loss to levee formation was applied to a subset of flows, n = 13, and suggests eruption rates and viscosities of ~30 – ~1.2 x 103 m3/s and 4.5 x 106 – ~3 x 107 Pa s, respectively. Emplacement times range from days to centuries indicating the necessity for long-term subsurface conduits capable of delivering enormous volumes of lava to the surface.
ContributorsPeters, Sean (Author) / Christensen, Philip R. (Thesis advisor) / Clarke, Amanda B (Committee member) / Fink, Jonathan H. (Committee member) / Whipple, Kelin X (Committee member) / Sharp, Thomas (Committee member) / Arizona State University (Publisher)
Created2020