Exoplanets are now known to be ubiquitous throughout the Galaxy. From the Kepler survey, we expect nearly every main-sequence star to form planetary systems during its formation phase. However, the detection limits of Kepler are confined to planets with short orbital periods, comparable to those in the inner solar system. Thanks to the long observational time baseline of the McDonald Observatory Radial Velocity (RV) Survey, we can identify gas giant planets in the outer regions of extrasolar planetary systems. The statistics of such planets are not well known, and are important for understanding the physics behind planet formation and migration. In this dissertation, I detail the discovery of five giant exoplanets on long-period orbits–so-called “Jupiter analogs.” For two systems of giant planets discovered through our survey, pairs of planets follow closely-packed orbits, creating the possibility for dynamical instability. I therefore examine the orbital resonances that allow these planets to avoid gravitational disruption. Because we see an abundance of small, potentially habitable exoplanets in the Kepler data set, current and upcoming exoplanet surveys concentrate on finding Earth-mass planets orbiting stars near enough to facilitate detailed follow-up observations. Particularly attractive targets are cool, low-mass “M dwarf” stars. Their low masses (and thus higher RV amplitudes from exoplanets) and close-in habitable zones allow for relatively quick detection of low-mass planets in the habitable zone. However, the RV signals of such planets will be obscured by stellar magnetic activity, which is poorly understood for M stars. In an effort to improve the planet detection capabilities of our M dwarf planet survey, I have conducted a detailed investigation of the magnetic behavior of our target stars. I show that, while stellar activity does not appear to systematically influence RV measurements above a precision level of ∼ 5 m/s, activity cycles can occasionally produce RV signals in excess of 10 m/s. Additionally, I show that long-term, solar-type stellar activity cycles are common amongst our M dwarf targets, although they are significantly less frequent than for FGK stars. In the case of GJ 328, I have discovered a magnetic activity cycle that appears in the RV data, causing the giant planet around the star to appear to be on a more circular orbit than indicated by the activity-corrected data. Such corrections are essential for the discovery of Earthlike exoplanets. / text

The Proterozoic period saw some of the most fundamental revolutions in the biological and geological world. During this period, life diversified and set the stage for the radiation of multicellular life, altering the face of the planet in the process. The fossil record of this time is not yet fully understood, and a revisitation of a historically reported fossil deposit in the 1 Ga Torridon rocks of northwest Scotland shows that they host the fossils of the earliest non-marine eukaryotes, as well as a full and diverse fossil assemblage preserved in sedimentary phosphates and shales. Fine scale sedimentology of the fluvio-lacustrine rocks of the Torridon Group reveals them to be laid down in a laterally variable basin with distinctly different palaeoenvironments. The resident biota is seen to be similarly variable between lithofacies. New criteria for classifying taphonomic effects are presented, and used to characterise assemblages from different palaeoenvironments, with broader applications beyond this study. The Torridon rocks are also host to macrostructures on the surfaces and soles of beds, and these are interpreted as of likely biological origin, with their variability mapped between different lithofacies. High-resolution studies of both the preserved biota and the mineralogy of the preserving medium reveal in detail not only the fine scale structure of the fossil organisms, but also the reasons for their exceptional preservation. Phosphate is analysed in detail to explain its enigmatic occurrence in Proterozoic lakes. To place the Torridon deposits in context, both older and younger rocks were examined in comparison, from the 2 Ga Gunflint Formation of Ontario, Canada, and the Precambrian-Cambrian successions of eastern Newfoundland respectively. New finds of phosphate in these rocks help to reveal biochemical interactions and evolution on the early Earth, with implications for further understanding life on our own planet and elsewhere.

In a multi-planet system, gravitational interactions cause orbital eccentricity variations. For non-resonant systems, classical secular theory reveals that the eccentricities are vector sums of contributions from several eigenmodes. Examination of the eigenvectors often reveals subsets of planets that interact especially strongly as dynamical groups. Perturbations from other sources, such as tides, are shared among the planets through the secular interactions. If one planet's eccentricity is tidally damped, all the eigenmodes damp so as to leave a signature on their amplitudes. Therefore, if one desires to include some a priori tidal damping in an orbital fit, solutions should not assume the current eccentricity of that planet to be low, but rather for the eigenmodes that damp quickly to have low amplitude. The tidally perturbed planet may retain a substantial eccentricity, because some eigenmodes will be longer-lived. The secular eigenmodes, including relative damping rates, have been calculated for all 72 non-resonant extra-solar systems with adequate data. Tides also affect evolution of planets' semi-major axes, which is coupled with eccentricity evolution. A planet that, alone, would be quickly circularized so as to not experience much semi-major axis migration, could rapidly be forced into the star in the presence of an outer planet. Also, though such an inner planet may now be gone, the eccentricity of the outer planet could have been damped due to tides that acted on the inner planet. Any inferences about the primordial orbits of observed planets must consider these effects. For systems where the inner planet has not yet reached the star, the planets' eccentricities can be constrained for any particular assumed tidal dissipation factor Q', e.g. for the KOI-543 system, if the inner planet is rocky, the eccentricities must be<0.001. The habitable zone around low-mass stars is close to the star, precisely where tides are important. Low-mass stars are very long lived, and can be very old currently. A habitable planet likely needs tectonics for cycles that regulate the atmosphere, but a planet's internal heat will decay over long timescales. However, an outer planet could maintain the inner planet's eccentricity, allowing tidal heating to maintain long-term habitability. Secular interactions, coupled with tidal effects, may be critical for planetary habitability.

While several lines of evidence strongly hint at the biological importance of impact-induced hydrothermal systems during the impact cataclysm at ~3.9 Ga, these systems are not well understood. There is unambiguous evidence of hydrothermal activity at many terrestrial craters, but the available samples represent a very limited number of crater diameters and locations within the crater. Therefore, computer models are crucial for learning how impact-induced hydrothermal systems work, how long they last, and whether they provide suitable environments for thermophilic microorganisms. This dissertation presents detailed simulations of hydrothermal activity at the terrestrial craters Chicxulub and Sudbury, as well as at range of crater sizes on early Mars. A well-established computer code HYDROTHERM was used. The models for terrestrial craters were constrained by seismic, magnetic, and gravity surveys, as well as petrological, mineralogical, and chemical analyses of samples (by others).Sudbury crater is ~180 km in diameter, and 1.85 Ga. Simulation results indicate that a hydrothermal system at Sudbury crater remained active for several hundred thousand to several million years, depending on assumed permeability, and produced habitable volumes of up to ~20,000 km^3.Chicxulub crater is also ~180-km in diameter, but only 65 Ma. The lifetime of the hydrothermal system ranges from 1.5 Ma to 2.3 Ma depending on assumed permeability. The temperatures and fluxes observed in the model are consistent with alteration patterns observed by others in borehole samples.Another set of simulations modeled post-impact cooling of hypothetical craters with diameters of 30, 100, and 180 km in an early Martian environment. System lifetimes, averaged for all permeability cases examined, were 67,000 years for the 30-km crater, 290,000 years for the 100-km crater, and 380,000 for the 180-km crater. Also, an ap-proximation of the thermal evolution of a Hellas-sized basin (~2000 km) suggests poten-tial for hydrothermal activity for ~10 Myr after the impact. The habitable volume reached a maximum of ~6,000 km^3 in the 180-km crater model.Possible morphological and mineralogical signs of hydrothermal activity in Martian craters were observed, both in this work and by others. These observations, while by no means definitive, are generally consistent with model predictions.

Studies of carbon's evolutionary path have been conducted via millimeter and submillimeter observations of circumstellar envelopes (CSEs), planetary nebulae (PNe), molecular clouds and comets. The 12C/13C isotope ratio was measured in Galactic molecular clouds using the CN isotopologs. A gradient of 12CN/13CN was determined to be 12C/13C = 6.01 DGC +12.28, where DGC is distance from the Galactic center. The results of CN are in agreement with those of CO and H2CO indicating a true ratio not influenced by fractionation effects or isotope-selective photodissociation. The 12C/13C isotope ratios in the envelopes of various types of stars were also measured from both CO and CN isotopologs. Such objects as carbon and oxygen-rich asymptotic giant branch (AGB) stars, supergiants, planetary nebulae, and S-type stars were observed. Results from this study indicate 12C/13C values for supergiants ~ 10 and AGB stars 12C/13C ~ 20- 76. Theory would suggest a lower ratio for objects undergoing third dredge-up, though this is seemingly not the case. Multiple carbon-bearing species including CO, HCN, HNC, CN, CS, and HCO+ have also been observed towards the oxygen-rich supergiant, VY CMa. This object has recently revealed a unique chemistry where carbon is not solely contained in CO, and may play a more important role in the chemical network of oxygen-rich circumstellar envelopes. Additionally, observations of species with carbon- carbon bonds, such as CCH and c-C3H2, have been conducted towards evolved planetary nebulae, such as the Helix and Ring nebulae. There is a close agreement in the inventories of species found in PNe and diffuse clouds, suggesting a potential molecular precursor to the interstellar medium. Observations of carbon-bearing species (H2CO and CO) in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT), and C/2002 T7 (LINEAR) have been conducted. Formaldehyde is known to have an extended distribution in these objects, likely arising from silicate-organic grains. Evidence of cometary fragmentation was also obtained for H2CO in comet T7 LINEAR as well as for HNC and HCO+ in Hale-Bopp. Such events could contribute to planetary distribution of organics.

Neste trabalho, criticamos a forma como alguns temas básicos da Física são expostos e são estudados ao longo do Ensino Médio. O assunto escolhido por nós foi a “Aplicação da Astronomia ao Ensino de Física com ênfase em Astrobiologia”. Este projeto tem como objetivo introduzir e estimular os alunos do 2º ano do Ensino Médio ao campo da Astronomia, utilizando-se de conhecimentos pré-adquiridos de Física da primeira série do Ensino Médio, e com ênfase em um tema bastante atual e em forte desenvolvimento, a Astrobiologia. O desenvolvimento do projeto proporcionou então o aprendizado de novos conceitos e áreas de Física, ainda não formalmente estudados. O projeto aborda desde um histórico da Astronomia, passando por um panorama geral da Astronomia contemporânea, até a sua relação com outras disciplinas, como Física, Química e Biologia, usando como eixo a Astrobiologia. Nestes contextos foram introduzidos conceitos básicos de diferentes áreas da Física, incluindo aquelas que são abordadas no decorrer dos dois últimos anos do Ensino Médio. Este projeto resultou na produção de um CD, onde está contido todo o material aplicado nas aulas com o formato “PowerPoint”. O CD inclui também explicações detalhadas para o professor sobre cada aula, sendo que estas notas de aula estão no formato de texto mais usual, “Microsoft Word”. Dessa forma, professores terão em mãos um roteiro de fácil acesso para que possam se orientar em suas aulas. Obtivemos resultados bastante significativos após a aplicação deste projeto. Tais resultados são demonstrados nas tabelas e gráficos apresentados no decorrer desta dissertação, e foram considerados satisfatórios por nós, demonstrando com clareza que a necessidade de atualizarmos e inovarmos o conhecimento em Física torna-se um fato notório. Com este trabalho, esperamos poder contribuir estimulando a criatividade e a curiosidade dos alunos para um tema merecedor de toda a nossa atenção. / In this work, we criticize the way some basic themes of Physics are presented and studied during High School. The subject chosen was “Use of Astronomy in the Physics Teaching with emphasis in Astrobiology”. This project´s goal is to introduce and stimulate junior High School students to the Astronomy field, making use pre-acquired knowledge from the previous series, and with emphasis in a current theme undergoing rapid growth: Astrobiology. The project development was meant to lead to learning of new concepts and areas of Physics, not studied previously. The project has started with the History of Astronomy, passed through a broad view of contemporary Astronomy, stressing its relation with other disciplines, such as Physical and Chemical sciences and Biology and always using Astrobiology as a defining axis. In these contexts basic concepts of different areas of Physics are introduced, including those that are taught during the two last years of High School. This project has led to the production of a CD, which contains the multimedia material applied in the classroom, in “PowerPoint” format. The CD includes full explanations about each class to interested teachers; these lecture notes are in the more usual “Microsoft Word” format. Thus, teachers will have in hands an easy access script to guide themselves through their lectures. The results we obtained with the application of this project are significant. They are shown as tables and graphs throughout the text. The very satisfactory outcome of the project clearly shows the need for an updated and innovative way of learning and teaching Physics. We hope this work may have stimulated the curiosity and creativity of students towards learning such an important theme.

Neste trabalho, criticamos a forma como alguns temas básicos da Física são expostos e são estudados ao longo do Ensino Médio. O assunto escolhido por nós foi a “Aplicação da Astronomia ao Ensino de Física com ênfase em Astrobiologia”. Este projeto tem como objetivo introduzir e estimular os alunos do 2º ano do Ensino Médio ao campo da Astronomia, utilizando-se de conhecimentos pré-adquiridos de Física da primeira série do Ensino Médio, e com ênfase em um tema bastante atual e em forte desenvolvimento, a Astrobiologia. O desenvolvimento do projeto proporcionou então o aprendizado de novos conceitos e áreas de Física, ainda não formalmente estudados. O projeto aborda desde um histórico da Astronomia, passando por um panorama geral da Astronomia contemporânea, até a sua relação com outras disciplinas, como Física, Química e Biologia, usando como eixo a Astrobiologia. Nestes contextos foram introduzidos conceitos básicos de diferentes áreas da Física, incluindo aquelas que são abordadas no decorrer dos dois últimos anos do Ensino Médio. Este projeto resultou na produção de um CD, onde está contido todo o material aplicado nas aulas com o formato “PowerPoint”. O CD inclui também explicações detalhadas para o professor sobre cada aula, sendo que estas notas de aula estão no formato de texto mais usual, “Microsoft Word”. Dessa forma, professores terão em mãos um roteiro de fácil acesso para que possam se orientar em suas aulas. Obtivemos resultados bastante significativos após a aplicação deste projeto. Tais resultados são demonstrados nas tabelas e gráficos apresentados no decorrer desta dissertação, e foram considerados satisfatórios por nós, demonstrando com clareza que a necessidade de atualizarmos e inovarmos o conhecimento em Física torna-se um fato notório. Com este trabalho, esperamos poder contribuir estimulando a criatividade e a curiosidade dos alunos para um tema merecedor de toda a nossa atenção. / In this work, we criticize the way some basic themes of Physics are presented and studied during High School. The subject chosen was “Use of Astronomy in the Physics Teaching with emphasis in Astrobiology”. This project´s goal is to introduce and stimulate junior High School students to the Astronomy field, making use pre-acquired knowledge from the previous series, and with emphasis in a current theme undergoing rapid growth: Astrobiology. The project development was meant to lead to learning of new concepts and areas of Physics, not studied previously. The project has started with the History of Astronomy, passed through a broad view of contemporary Astronomy, stressing its relation with other disciplines, such as Physical and Chemical sciences and Biology and always using Astrobiology as a defining axis. In these contexts basic concepts of different areas of Physics are introduced, including those that are taught during the two last years of High School. This project has led to the production of a CD, which contains the multimedia material applied in the classroom, in “PowerPoint” format. The CD includes full explanations about each class to interested teachers; these lecture notes are in the more usual “Microsoft Word” format. Thus, teachers will have in hands an easy access script to guide themselves through their lectures. The results we obtained with the application of this project are significant. They are shown as tables and graphs throughout the text. The very satisfactory outcome of the project clearly shows the need for an updated and innovative way of learning and teaching Physics. We hope this work may have stimulated the curiosity and creativity of students towards learning such an important theme.

Neste trabalho, criticamos a forma como alguns temas básicos da Física são expostos e são estudados ao longo do Ensino Médio. O assunto escolhido por nós foi a “Aplicação da Astronomia ao Ensino de Física com ênfase em Astrobiologia”. Este projeto tem como objetivo introduzir e estimular os alunos do 2º ano do Ensino Médio ao campo da Astronomia, utilizando-se de conhecimentos pré-adquiridos de Física da primeira série do Ensino Médio, e com ênfase em um tema bastante atual e em forte desenvolvimento, a Astrobiologia. O desenvolvimento do projeto proporcionou então o aprendizado de novos conceitos e áreas de Física, ainda não formalmente estudados. O projeto aborda desde um histórico da Astronomia, passando por um panorama geral da Astronomia contemporânea, até a sua relação com outras disciplinas, como Física, Química e Biologia, usando como eixo a Astrobiologia. Nestes contextos foram introduzidos conceitos básicos de diferentes áreas da Física, incluindo aquelas que são abordadas no decorrer dos dois últimos anos do Ensino Médio. Este projeto resultou na produção de um CD, onde está contido todo o material aplicado nas aulas com o formato “PowerPoint”. O CD inclui também explicações detalhadas para o professor sobre cada aula, sendo que estas notas de aula estão no formato de texto mais usual, “Microsoft Word”. Dessa forma, professores terão em mãos um roteiro de fácil acesso para que possam se orientar em suas aulas. Obtivemos resultados bastante significativos após a aplicação deste projeto. Tais resultados são demonstrados nas tabelas e gráficos apresentados no decorrer desta dissertação, e foram considerados satisfatórios por nós, demonstrando com clareza que a necessidade de atualizarmos e inovarmos o conhecimento em Física torna-se um fato notório. Com este trabalho, esperamos poder contribuir estimulando a criatividade e a curiosidade dos alunos para um tema merecedor de toda a nossa atenção. / In this work, we criticize the way some basic themes of Physics are presented and studied during High School. The subject chosen was “Use of Astronomy in the Physics Teaching with emphasis in Astrobiology”. This project´s goal is to introduce and stimulate junior High School students to the Astronomy field, making use pre-acquired knowledge from the previous series, and with emphasis in a current theme undergoing rapid growth: Astrobiology. The project development was meant to lead to learning of new concepts and areas of Physics, not studied previously. The project has started with the History of Astronomy, passed through a broad view of contemporary Astronomy, stressing its relation with other disciplines, such as Physical and Chemical sciences and Biology and always using Astrobiology as a defining axis. In these contexts basic concepts of different areas of Physics are introduced, including those that are taught during the two last years of High School. This project has led to the production of a CD, which contains the multimedia material applied in the classroom, in “PowerPoint” format. The CD includes full explanations about each class to interested teachers; these lecture notes are in the more usual “Microsoft Word” format. Thus, teachers will have in hands an easy access script to guide themselves through their lectures. The results we obtained with the application of this project are significant. They are shown as tables and graphs throughout the text. The very satisfactory outcome of the project clearly shows the need for an updated and innovative way of learning and teaching Physics. We hope this work may have stimulated the curiosity and creativity of students towards learning such an important theme.

Raman spectroscopy is a powerful tool for identification both inorganic and organic compounds including microbial biomolecules. Together with the fact, that it is considered to be the important nondestructive instrument for use on Mars within future robotic missions, it is necessary to assess its capabilities in scenarios relevant for both Martian and terrestrial conditions. In this work, the potential of Raman spectrometry was tested - including both bench-top laboratory systems as well as portable counterparts - to detect traces of life within evaporitic matrices through biomolecular identification. Due to their chemical and physical nature resulting in optical properties, pigments are important organic compounds in Raman spectroscopic analysis using visible excitation. Hence in this work we have focused on the Raman spectroscopic identification of pigments as biomarkers with relevance for investigation of life in both extreme terrestrial and potentially extraterrestrial environments. Results of methodical work are presented in Appendices I to III, dealing particularly with β-carotene as a model carotenoid pigment. The concentration limits of this biomarker in three different evaporitic matrices (halite, gypsum and epsomite) have been determined for artificially prepared powdered mixtures alone...

abstract: Jupiter’s moon Europa is an active target of research because of its unique geology and its potential for habitability. Europa’s icy chaos disrupts and transforms the previous terrain, suggesting melting is involved. Chaos occurs alongside several types of endogenic surface features. These microfeatures are under <100 km2 in area and include uplifts and domes, pits, spots, and hybrid features. The distribution of microfeatures is known in the ~10% of the Europa’s surface that are covered by the regional mosaics (“RegMaps”). The efforts to connect microfeature formation to any kind of heat transport in Europa are confounded because microfeatures are difficult to identify outside of RegMaps because of low image resolutions. Finding microfeatures outside of RegMaps would provide new observational constraints for microfeature formation models. First, I mapped microfeatures across four of Europa’s RegMaps and validated them against other mapping datasets. Microchaos features are the most numerous, followed by pits, domes, then hybrids. Spots are the least common features, and the smallest. Next, I mapped features in low-resolution images that covered the E15RegMap01 area to determine error rates and sources of omission or misclassification for features mapped in low-resolution images. Of all features originally mapped in the RegMap, pits and domes were the least likely to be re-mapped or positively identified (24.2% and 5%, respectively). Chaos, spots, and hybrids were accurately classified over 70% of the time. Quantitatively classifying these features using discriminant function analysis yielded comparable values of accuracy when compared to a human mapper. Finally, nearest-neighbor clustering analyses were used to show that pits are clustered in all regions, while chaos, domes, and hybrids vary in terms of their spatial clustering. This work suggests that the most likely processes for microfeature formations is either the evolution of liquid water sills within Europa’s ice shell or cryovolcanism. Future work extending to more areas outside of the RegMaps can further refine microfeature formation models. The detection of liquid water at or near the surface is a major goal of multiple upcoming Europa missions; this work provides predictions that can be directly tested by these missions to maximize their scientific return. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2019