Patrick Barth

I completed my PhD at the University of St Andrews in the Schools of Physics and Astronomy and Earth and Environmental Sciences and visiting researcher at the Space Research Institute at the Austrian Academy of Sciences in Graz. My research was focusing on the effect of lighting on the atmospheric chemistry of Earth and other planets and investigating its impact on the origin of life. This included Miller-Urey like sparking experiments and simulations of chemical processes in planetary atmospheres.

Lightning might have played an important role in the origin of life, and we know that it can produce nutrients for life in the atmosphere of the early Earth. But so far it was not possible to say if lightning was an important source of nutrients for the earliest life on Earth. We conducted spark experiments in our lab with different gas mixtures: N2 and O2 for the modern Earth and N2 and CO2 for early Earth. We then measured the concentration of the nitrogen products such as nitrite and nitrate and their isotopic composition. We found lightning can efficiently produce nitrogen oxides in both O2- and CO2-rich atmospheres, which beyond Earth, provides a potential source of nutrients for life on exoplanets. Our nitrogen signature for lightning cannot explain nitrogen samples in the Archean sedimentary rock record, suggesting that lightning was not a major source of nutrients for life on early Earth and that biological nitrogen fixation developed very early. However, there is one set of samples from the Isua Greenstone Belt in Greenland from nearly 3.8 billion years ago, that shows an isotope signature that can be explained by a lightning contribution. And our isotopic signature can help to investigate the source of nitrate samples on Mars and potentially other bodies in the Solar System. For more information please check out our paper (DOI, Full text, Arxiv) and for a more detailed summary our Research Briefing (Full text).

We investigate the effect of stellar X-ray and UV (XUV) radiation, cosmic rays (CR), and stellar energetic particles (SEP, mainly protons) on the atmospheric chemistry of the hot Jupiter HD 189733b and identify key signatures of these interactions. We choose this planet because it is one of the best studied and observed exoplanets today, allowing us to optimize the model before later applications to habitable worlds. We use 3D simulations of HD 189733b’s atmosphere for the pressure-temperature profiles and XUV spectra of the host star from the MOVES collaboration. To model the chemical reactions, we use the STAND2019 network, which includes ion-neutral C/H/N/O chemistry. We study in detail the formation of the amino acid glycine and its precursors. Our results suggest that the CR and SEP influx enhances the formation of glycine, while XUV radiation leads to a depletion of glycine in the upper atmosphere. We identify ammonium (NH4+) as an important signature of CR and SEP influx, even though the degree of ionization of the atmosphere remains low. XUV radiation strongly ionizes the upper atmosphere, mainly producing H+ and He+. Ultimately, we show that high energy processes increase glycine and precursor production and thus may potentially play an important role in prebiotic chemistry. For more information please check out our paper (DOI, Arxiv).

Recent observations of the potentially habitable planets TRAPPIST-1 e, f, and g suggest that they possess large water mass fractions of possibly several tens of weight percent of water, even though the host star's activity should drive rapid atmospheric escape. These processes can photolyze water, generating free oxygen and possibly desiccating the planet. After the planets formed, their mantles were likely completely molten with volatiles dissolving and exsolving from the melt. To understand these planets and prepare for future observations, the magma ocean phase of these worlds must be understood. To simulate these planets, we have combined existing models of stellar evolution, atmospheric escape, tidal heating, radiogenic heating, magma-ocean cooling, planetary radiation, and water-oxygen-iron geochemistry. We present MagmOc, a versatile magma-ocean evolution model, validated against the rocky super-Earth GJ 1132b and early Earth. This model is part of the VPLanet code. We simulate the coupled magma-ocean atmospheric evolution of TRAPPIST-1 e, f, and g for a range of tidal and radiogenic heating rates, as well as initial water contents between 1 and 100 Earth oceans. We also reanalyze the structures of these planets and find they have water mass fractions of 0–0.23, 0.01–0.21, and 0.11–0.24 for planets e, f, and g, respectively. Our model does not make a strong prediction about the water and oxygen content of the atmosphere of TRAPPIST-1 e at the time of mantle solidification. In contrast, the model predicts that TRAPPIST-1 f and g would have a thick steam atmosphere with a small amount of oxygen at that stage. For all planets that we investigated, we find that only 3–5% of the initial water will be locked in the mantle after the magma ocean solidified. For more information please check out our paper (DOI, Arxiv) and our GitHub repository.

The Steiermark Schau is an exhibition presenting the diversity of the Austrian state of Styria. In 2023, the focus of this exhibition is "Diversity of life", and a central element will be an 800 squaremetre mobile pavilion. In cooperation with the IWF in Graz and following the theme "Atmospheres - Climate, Art, and Cosmos", a combination of art works and scientific reflections will be presented on a large projection space, encouraging the audience to think about the fragility of our own atmosphere in the context of the large diversity of extrasolar planets and their atmospheres. In preparation of this exhibition, it is my role to coordinate the cooperation between exoplanet scientists at the IWF and the organisers of the project as well as the participating artists.

"Around Distant Suns" is an anthology of nine science fiction stories, edited by Emma Puranen. Each story is written by a pair of one creative writer and one researcher of the St Andrews Centre for Exoplanet Science. I worked with Emma Puranen on the short-story "A Spark in a Flask" which follows a roboter who oversees giant spark experiments on a base on the moon, long after the last humans left. These experiments are designed to find under which conditions life might emerge in the presence of lightning and are similar to the famous Miller-Urey experiment and the experiments that I am conducting in my lab. "Around Distant Suns" is available at Guardbridge Books. "A Spark in a Flask" was selected for the Best of British Science Fiction 2021 award anthology.