August 29, 2025

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Speaker: Georgina Aitolo, PhD Candidate, The University of Texas at Austin

Title: Early impact crater hydrothermal systems are sites of high microbial diversity and biogeochemical cycling

Abstract: Impact crater hydrothermal systems, formed in the aftermath of asteroid and comet impacts, have been proposed as promising habitats for life, for example on early Earth. They are also regarded as potential locations to test the hypothesis of life on planetary bodies such as Mars, since they provide liquid water and active geochemical turnover. In the absence of newly formed impact craters on Earth, investigations on the primary colonists in impact hydrothermal systems have been confined to the search for fossil life or its isotopic signatures. To overcome this limitation, we created simulated microcosm hydrothermal systems in the laboratory using impact suevite from the Ries impact structure, Germany. We examined the formation of habitat space and microbial communities in the first weeks after the formation of the systems. The simulated hydrothermal systems varied by temperatures and hosted taxonomically different microbial communities which partitioned into distinct habitats, including oxidised rock surfaces and a sedimentary habitat. Progressively higher temperature favoured the growth of some bacteria phyla, including Bacillota, Bacillota_B, Bacillota_E. We observed the establishment of sulfate-reducing microorganisms and methanogenic archaea. Our data show that immediately after impact, hydrothermal systems can host diverse thermophilic ecosystems with potentially important influences on biogeochemical cycles, suggesting that impact hydrothermal systems can act as refugia for life.

Biography: Georgina Aitolo is a 3rd year PhD candidate in the Department of Microbiology (ILS), advised by Brett Baker in the Department of Integrative Biology. Her research spans microbial evolution, diversity and metabolism in coastal and extreme environment. She is currently investigating the establishment of microbial communities in simulated impact-craters hydrothermal systems by using computational approaches. Outside the lab, she loves reading, listening to music and spending some quality time with her family.

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Speaker: Nathanael Burns-Watson, Graduate Student, The University of Texas at Austin

Title: Determining The Host Stars of Exoplanets in Binary Star Systems

Abstract: A defining characteristic of exoplanet populations is the lack of planets between 1.8-2.0 Earth radii, known as the radius gap. The radius gap is thought to distinguish between terrestrial planets with little to no atmosphere and gaseous planets with substantial atmospheres. The radius gap is now thought to be absent among planets hosted in binary star systems. However, this assumes that all of the planets were orbiting the brighter primary star. In many cases, the radius of the planet would be significantly larger if it were orbiting the companion star. We are determining which star these planets are orbiting and revising their radius values in turn. We used data from the Kepler mission and transit refitting to compare transit and spectroscopic densities to determine the host stars and new planetary radii. We selected a sample of planets that would fall in the radius gap if they were orbiting the primary star, but would fall above the radius gap as sub-Neptunes if they were orbiting the secondary star. Our results will be discussed in this talk.

Biography:  I am a second-year graduate student in the Department of Astronomy working with Adam Kraus. I previously received my Bachelor’s in Astronomy from Case Western Reserve University. My research interests are in exoplanets and the formation of stars and planets.