Until the 1990s, the only known planets were those in our Solar System. Three decades later, several thousand exoplanets have been discovered orbiting stars other than the Sun, and substantial... Show moreUntil the 1990s, the only known planets were those in our Solar System. Three decades later, several thousand exoplanets have been discovered orbiting stars other than the Sun, and substantial efforts have been made to explore these strange new worlds through spectroscopic analyses of their atmospheres. In particular, high-dispersion spectroscopy has provided robust measurements of these objects, enabling investigations of the significant, outstanding questions of exoplanetary science: What kinds of planets exist beyond our Solar System? Of what are they made? How did they form? Is there life beyond Earth? This dissertation touches upon all of these topics. Chapter 2 details a study to understand the chemical composition of one of the most extreme exoplanets. Chapter 3 investigates the feasibility of studying the different isotopes of titanium in large gaseous exoplanets, which may provide insight into their formation. Chapter 4 presents an attempt to detect young, still-forming planets in an effort to better understand how this process works. Chapter 5 concludes this dissertation with an evaluation of the ability of large future telescopes to detect molecular oxygen in Earth-like exoplanets, which may trace the presence of life. Show less
This thesis is largely an experimental study on the formation of solid-state simple and complex organic molecules in the H2O-rich and CO-rich ice phases of dense interstellar clouds and dark cores.... Show moreThis thesis is largely an experimental study on the formation of solid-state simple and complex organic molecules in the H2O-rich and CO-rich ice phases of dense interstellar clouds and dark cores. Astronomical ice observations are also presented and are strongly linked to the experimental work. For decades, it has been realized that particularly complex organic molecules can be formed at extremely low temperatures with the aid of 'energetic' particles, such as UV photons. In this thesis, it is clearly shown that complex organic molecules can also be formed without 'energetic' particles. The experimental laboratory work is supported by computational calculations to constrain which molecules are more or less likely to form under the extreme conditions of interstellar clouds. Show less
During solar-type star formation, the chemistry evolves towards the formation of complex organic molecules, eventually setting the stage for the origin of life. This astrochemical evolution depends... Show moreDuring solar-type star formation, the chemistry evolves towards the formation of complex organic molecules, eventually setting the stage for the origin of life. This astrochemical evolution depends on the interaction between gas and microscopic interstellar grains, producing icy grain mantles. This thesis combines ice and gas-phase observations with astrophysically relevant laboratory simulations to constrain some of the key gas-grain processes. From Spitzer observations, the first simple ices, e.g. water and methane, form sequentially through condensation followed by an active surface chemistry, with more source-to-source variation the later in the sequence an ice forms. Close to the protostar the ices are heated. Experiments and their modeling have provided a generalized, quantitative understanding of the induced ice mixture evaporation and segregation, based on relative diffusion barriers alone. When no heat is available UV-induced evaporation still connects the ice and gas; UV photodesorption is found experimentally to be efficient with a similar yield for most ices. UV irradiation also converts simple ices into more complex species and this formation process has been quantified in situ for the first time. Based on these experiments, observations of complex organic molecules around protostars and in comets are readily explained by ice photochemistry. Show less
The search for organic molecules and traces of life on Mars has been a major topic in planetary science for several decades, and is the future perspective of several missions to Mars. In order to... Show moreThe search for organic molecules and traces of life on Mars has been a major topic in planetary science for several decades, and is the future perspective of several missions to Mars. In order to determine where and what those missions should be looking for, laboratory experiments under simulated Mars conditions have been performed. This thesis describes the effects of simulated martian surface conditions on organic material (amino acids) and living organisms (halophilic archaea). Experiments have been performed to study the stability of thin films of glycine and alanine against UV irradiation under different conditions. Thin films of glycine and alanine have a half-life of 22 ± 5 hours and 3 ± 1 hours, respectively, when extrapolated to Mars-like UV flux levels in vacuum. The presence of a 7 mbar CO2 atmosphere does not affect these destruction rates. Cooling the thin films to 210 K (average Mars temperature) lowers the destruction rate by a factor of 7. The intrinsic amino acid composition of two martian soil analogues, JSC Mars-1 and Salten Skov, has been investigated. The results demonstrated that these analogues are inappropriate for a life-science study in their raw state. Besides amino acids, the response of the halophilic archaea Natronorubrum sp. strain HG-1 to Mars-like conditions, such as low pressure, UV radiation and low temperatures, has been studied. From the results we concluded that this strain would not be a good model organism to survive on the surface of Mars. Show less
