Martian magmas are thought to be rich in chlorine compared with their terrestrial counterparts. Consistent with other Martian meteorites, apatite grains in Martian meteorite NWA 6234 are dominantly Cl-apatite suggesting that the parental magma to NWA 6234 may have been rich in Cl. Here we experimentally investigate the effect of chlorine on liquidus depression and near liquidus crystallization of a synthetic composition of NWA 6234 and compare these results with previous experimental results on the effect of chlorine on near-liquidus crystallization of surface basalts Humphrey and Fastball. Previous experimental results using two different starting synthetic Martian basalt compositions showed that the change of liquidus temperature is dependent on the bulk composition of the basalt. The effect of Cl on liquidus depression is greater for lower SiO2, higher Al2O3 magmas than higher SiO2, lower Al2O3 magmas. The bulk composition for this study has lower Al2O3 and high FeO contents than previous work; therefore, we can further constrain the effect of the bulk composition on the influence of chlorine on near-liquidus crystallization. High pressure and temperature crystallization experiments were performed at 1 GPa (10 Kbar) on a synthetic basalt, of the bulk composition of NWA 6234, with 0 - 4 wt% Cl added to the sample as AgCl. The results are consistent with previous notions that with increasing wt. % Cl in the melt, the crystallization temperature decreases. Importantly, our results have a liquidus depression ∆T (oC) from added chlorine that is intermediate between the two previous results, consistent with the difference in bulk composition. This suggests that the addition of Cl to the Martian mantle may lower the magma genesis temperature and potentially aid in the petrogenesis of Martian magmas.

abstract: Tempe Terra, Mars, has a complex history marked by volcanism and tectonism. Investigation results presented here build on previous work to better determine the volcanic history of the Tempe volcanic province by identifying and mapping previously undetected vents, characterizing all vents, identifying spatial and temporal trends in eruptive styles, comparing vent density to similar provinces such as the Snake River Plains of Idaho and Syria Planum and determining absolute age relationships among the volcanic features. Crater size-frequency distribution model ages of 120 Ma to 2.4 Ga indicate the province has been active for over half of the planet's history. During that time, age decreases from southwest to northeast, a trend that parallels the dominant orientation of faulting in the region, providing further evidence that volcanic activity in the region is tectonically controlled (or the tectonics is magmatically controlled). Morphological variation with age hints at an evolving magma source (increasing viscosity) or changing eruption conditions (decreasing eruption rate or eruption through thicker lithosphere). / Dissertation/Thesis / M.S. Geological Sciences 2012

Using the Mars Atmosphere and Volatile Evolution Neutral Gas and Ion Mass Spectrometer data, we investigate the possible impact of crustal magnetic fields on the thermal structure of the Martian upper atmosphere. Our analysis reveals a clear enhancement in temperature over regions with strong crustal magnetic fields during two deep dip campaigns covering the periods of April 17-22 and September 2-8, both in 2015. Several controlling factors, such as solar EUV irradiance, relative atomic O abundance, and non-migrating tides, do not help to explain the observed temperature enhancement, and a magnetically driven scenario is favored. We evaluate the roles of several heating mechanisms that are likely modulated by the presence of crustal magnetic fields, including Joule heating, ion chemical heating, as well as electron impact heating via either precipitating solar wind electrons or locally produced photoelectrons. The respective heating rates of these mechanisms are substantially lower than the solar EUV heating rate, implying that none of them is able to interpret the observations.

The Mars Science Laboratory rover, Curiosity, is using a comprehensive scientific payload to explore rocks and soils in Gale crater, Mars. Recent investigations of the Bagnold Dune Field provided the first in situ assessment of an active dune on Mars. The Chemistry and Mineralogy (CheMin) X-ray diffraction instrument on Curiosity performed quantitative mineralogical analyses of the <150m size fraction of the Namib dune at a location called Gobabeb. Gobabeb is dominated by basaltic minerals. Plagioclase, Fo56 olivine, and two Ca-Mg-Fe pyroxenes account for the majority of crystalline phases along with minor magnetite, quartz, hematite, and anhydrite. In addition to the crystalline phases, a minimum similar to 42wt % of the Gobabeb sample is X-ray amorphous. Mineralogical analysis of the Gobabeb data set provides insights into the origin(s) and geologic history of the dune material and offers an important opportunity for ground truth of orbital observations. CheMin's analysis of the mineralogy and phase chemistry of modern and ancient Gale crater dune fields, together with other measurements by Curiosity's science payload, provides new insights into present and past eolian processes on Mars.

Magmatism is a critical process throughout the geological history of Earth and Mars, and one of the few processes capable of producing significant changes in the Martian surface and subsurface past the Noachian. The interaction between mafic magmatism and host rock has the potential to contribute to the surface volatile species, chief among which is sulfur. On Earth, mafic magmas intruding sulfur-rich sediments are rare; however, sulfur–rich soils exist with a near global extent on Mars, and evidence exists for both recent and ancient mafic magmatism. The intrusion of mafic magmas into sulfur-rich sediments is therefore expected on Mars, and is especially pertinent concerning proposed landing site for the ESA ExoMars mission, and the landing site of the NASA Mars 2020 mission, both of which are in proximity to a potential volcanic capping unit in direct contact with sulfate bearing sediments. Here we investigate a terrestrial analog in the San Rafael Swell on the Colorado Plateau in which numerous mafic dikes intrude, alter, and bake sulfur-rich sediments. Mafic dikes intruding the Curtis, Entrada Sandstone, and Carmel Formations act as analogs for volcanic/sediment interaction on Mars, specifically for Jezero Crater, Mawrth Vallis, and N-E Syrtis Major. Using Mars relevant instruments, mineralogical changes with respect to distance from the magmatic intrusion, as well as the spatial resolution necessary to detect these changes, are constrained. The investigated analogs are discovered to be dynamic, and similar systems on Mars will likely require both orbital and in-situ measurements to be detected due to resolution constraints.

Historically, studying the Martian ionosphere has been difficult due to the lack of dedicated instruments for electron density measurements in the orbit of Mars. However, since 2005, radio occultation measurements have been supplemented by Mars Express MARSIS remote sounder data and, more recently, by data from the MAVEN LPW Langmuir probe since 2014. The ionosphere of Mars is an interesting system, because Mars as one of the two solar system planetary bodies without an intrinsic magnetic field has highly localised crustal magnetic fields. The Chapman model describes the main layer of the ionosphere surprisingly well. Nevertheless, the crustal magnetic fields and other parameters potentially influence the ionosphere formation and topology. Combining the recent vast electron density data set, the Mars Global Surveyor crustal magnetic field map, and F10.7 solar radio flux measurements carried out at the Earth, a detailed study of the influence of these parameters can be conducted. To study the influence of these parameters as well as solar zenith angle on electron densities in the Martian ionosphere, we study magnitude of deviations from the established Chapman model. Furthermore, we use the Kolmogorov's 5/3 power law to investigate a possible dependence of its parameters characterising power and dissipation...

Escherichia coli and Serratia liquefaciens, two common microbial spacecraft contaminants known to replicate under low atmospheric pressures of 25 mb, were tested for growth and survival in simulated martian conditions. Stressors of high salinity, low temperature, and low pressure were screened alone and in combination to determine how they might affect microbial activity. Growth and survival of E. coli and S. liquefaciens under low temperatures (30, 20, 10, or 5 °C) with increasing concentrations (0, 5, 10, or 20 %) of three salts believed to be present on the surface of Mars (MgCl2, MgSO4, NaCl) were monitored over 7 d. Results indicated higher growth rates for E. coli and S. liquefaciens at 30 and 20 °C and in solutions without salt or in 5 % concentrations. No increase in cell density occurred under the highest salt concentrations at any temperatures tested; however, survival rates were high, especially at 10 and 5 °C. Growth rates of E. coli and S. liquefaciens with and without salts at 1013, 100, or 25 mb of total atmospheric pressure were robust under all pressures. In a final experiment, E. coli was maintained in Mars-simulant soils in a Mars Simulation Chamber. Temperatures within the chamber were changed diurnally from -50 °C to 20 °C; UV light was present during daytime operation (8 hrs), and pressure was held at a constant 7.1 mb in a Mars atmosphere for 7 d. Results from the full-scale Mars simulation indicated that E. coli failed to increase its populations under simulated Mars conditions, but was not killed off by the low pressure, low temperature, or high salinity conditions. Escherichia coli, and potentially other bacteria from Earth, may be able to survive on Mars. Surviving bacteria may interfere with scientific studies or, if future conditions become more favorable for microbial growth, modify the martian atmosphere and biogeochemistry.

Atmospheric tides significantly influence the dynamics of Mars' upper atmosphere. The impact of tides on the mean state of the present-day Martian atmosphere is especially large at high altitudes. Certain tides can propagate away from the region of generation in the lower atmosphere and reach the upper atmosphere, where they can achieve significant amplitudes. Such vertically propagating tides constitute one of the primary mechanisms by which energy and momentum are transferred between atmospheric layers. Much of the initial evidence of tides reaching the upper atmosphere came from the Mars Global Surveyor mission (MGS). The MGS aerobraking densities revealed large-amplitude large-scale wavenumber-2 signature attributed to a class of tides known as nonmigrating tides. Recent observations from the Mars Atmosphere and Volatile Evolution mission (MAVEN) suggest that tides producing wavenumber-2 and wavenumber-3 structures are strongest in the upper atmosphere in a fixed local time reference frame. However, the energy carried by these tides and the region of deposition has not been well characterized. Moreover, it has been challenging to obtain a global understanding of the behavior of tides due to observations being limited in altitude combined with sparse geographical coverage. Over the recent years, multiple missions have been active simultaneously, presenting an excellent opportunity to understand the nature and behavior of vertically propagating tides from an observational lens. This dissertation aims to infer the vertical propagation characteristics of tides by combining the relative strengths of in situ and remotely sensed data from multiple instruments on different spacecrafts over a broad range of altitudes. Estimates of tidal amplitudes for five cases around the equator are presented. Hemispherical differences in the dominant wavenumber are reported in the middle atmosphere. It is seen that the wavenumber structure in the upper atmosphere reflects that seen in the lower atmosphere about half the time. Of note is that most of the energy carried by the wave is dissipated by ~90 km. This analysis is also extended to high latitudes, where wave signatures are identified in the upper atmosphere using solar occultation observations for the first time. The eastward propagating non-migrating tides are shown to dominate the tidal spectrum. A key finding is that the relative importance of the tides with different periods is more significant at high latitudes, leading to a change in the observed wavenumber structure with local time. Comparison to physics-based models reveal that the model performs generally better at low latitudes than high latitudes. / Doctor of Philosophy / Various waves exist in nature, some visible like ocean tides, others unseen like sound waves, but their effects are undoubtedly perceptible. Often when we think of waves, we envision those that ripple across the ocean, but the atmosphere also hosts a multitude of waves, driving a large part of our weather systems. If you consider the atmosphere a fluid, it carries waves of different sizes. One such category of waves, on a scale comparable to the planet's size, is called atmospheric tides. These atmospheric tides are classified into 'migrating tides' and 'non-migrating tides'. 'Nonmigrating tides' are generated near the surface. Some of these tides can propagate upward, reaching what is referred to as the 'upper atmosphere'. As they ascend, these tides grow in size, similar to how an ocean wave lifts a boat higher as the wave itself grows larger. The tides that reach the upper atmosphere can cause considerable displacement of atoms and molecules. These tides are particularly large on Mars, presenting a challenge for spacecraft that rely on precise knowledge of the total amount of molecules in the upper atmosphere for slowing down the spacecraft. This study aims to understand the nature of these tides as they propagate into the upper atmosphere and how they evolve as they pass through different regions of the Martian atmosphere. To do this, combining observations from multiple spacecraft is necessary, as a single spacecraft's observations are insufficient for probing these tides. One notable finding is that the tides lose most of their energy by the time they reach an altitude of 90 km, but they are still noticeable in the upper atmosphere. Previous work has relied on 'snapshots' in time to identify the strongest wave. This approach may work well near the equator, but this study reveals that closer to the poles, the strongest wave can change due to the presence of tides with different periods (24 hr, 12 hr, and so on).

<p dir="ltr">Martian ice, especially its large polar ice caps, holds an important key to interpreting Mars’ past climate. Mars’ polar ice deposits are comprised of layers of ice and dust, and are thought to preserve a record of climate throughout their evolution. Smaller deposits also exist nearby, located in craters that may help prolong their preservation. Ground penetrating radar is an effective tool for understanding Martian ice, as it can probe the subsurface and place constraints on the properties of buried materials. Through a combination of radar remote sensing observations, modeling, and lab experiments, we analyze the dusty ice stratigraphies in Mars polar regions as well as the layer properties that make up the signals in the radar observations of these stratigraphies. We find that the northern ice deposits seem to have more consistency across the north polar region, and have identified at least 2 sub-populations of ice deposits in the south polar regions. This shows that the northern deposits hold one more consistent depositional history, and that there may be multiple depositional histories recorded in the southern deposits. The properties of the layers that make up these deposits are a product of their depositional environment, so studying the physical properties can help us better decode these depositional histories. Through experiments and modeling we find that brighter reflectors are caused by thin, dusty layers. The results in this dissertation have direct implications for interpretation of radar sounding data on Mars for climate studies, especially observations of the Polar Layered Deposits.</p>

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