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Abstract: Earth’s core-mantle boundary features a complex landscape of multi-scale structures whose heterogeneous compositions and physical properties likely influence key phenomena in Earth’s interior. Interdisciplinary advances in the past decade have shown that mountain-scale structures discovered at roots of mantle plumes may be strongly enriched in solid FeO, a material exhibiting various unique but poorly constrained properties at deep Earth conditions.

Here, Dr. Dobrosavljevic will share his recent experimental results on the melting of FeO, as well as theoretical work on the material’s insulator-metal transition at these extreme conditions. These findings suggest the presence of solid FeO-rich regions at Earth’s mantle base can explain independent observations from multiple geophysical probes.

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Abstract: I will be discussing my previous search for nearby companion planets to hot Jupiters, the calculation of their occurrence rates, and the implications of the formation pathways of these systems. I will also bookend the life of hot Jupiters with a discussion on the orbital decay of hot Jupiters into their host stars and the new possibilities emerging to detect this phenomenon. Time permitting, I will also present my efforts to identify and statistically validate the best-in-class targets for atmospheric characterization with JWST and future missions.

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Abstract: Presolar stardust grains are tiny and rare components of meteorites. They were produced in the winds and explosions of ancient dying stars and were part of the molecular cloud from which the Solar System formed. By analyzing their compositions, we can learn how stars synthetized elements and their isotopes. Studying presolar grains is also the only known way of directly examining some of the building blocks of the Solar System in the laboratory. They can tell us what type of material and which processes ultimately formed the Sun and planets. In this talk, we will explore a new dataset of presolar grain abundances and multi-element isotopic compositions collected with the Carnegie NanoSIMS. The samples include previously unstudied meteorites and material recently returned from asteroid Ryugu by the Hayabusa2 spacecraft. We will examine what these presolar grains can tell us about their origin and the early evolution of the solar system.

Speaker bio >>

Abstract: I will be discussing my previous search for nearby companion planets to hot Jupiters, the calculation of their occurrence rates, and the implications of the formation pathways of these systems. I will also bookend the life of hot Jupiters with a discussion on the orbital decay of hot Jupiters into their host stars and the new possibilities emerging to detect this phenomenon. Time permitting, I will also present my efforts to identify and statistically validate the best-in-class targets for atmospheric characterization with JWST and future missions.

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Abstract: On January 15, 2022, the largest explosive eruption instrumentally recorded occurred at Hunga Tonga-Hunga Ha’apai volcano in the Tonga-Kermadec island arc. In this talk, I will first summarize the 2022 eruptive sequence and the multidisciplinary observations that made this eruption exceptional. I will then show how we can use gravity data derived from satellite altimetry to determine the architecture of the magmatic system. Multibeam bathymetry data acquired post-eruption reveal the seafloor changes associated with the eruption including the dramatic ~850m caldera collapse. We will see how the eruption and associated caldera collapse reorganized magma storage under Hunga Tonga volcano.

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Abstract: Properties of carbon at extreme pressures and temperatures are of critical importance for constructing interior models of carbon-rich exoplanets. Among the questions that have long perplexed the scientific community are the existence and potential synthesis of high-pressure post-diamond carbon phases, and the inelastic response of diamond to strong shock compression. In particular, very recent ramp compression and X-Ray diffraction experiments at the National Ignition Facility (NIF) challenged theoretical prediction of the existence of a high-pressure BC8 post-diamond phase by compressing diamond to extreme pressures up to 20 Mbar. In this talk, Dr. Oleynik will describe recent advances in simulating atomic-scale dynamics of material’s response at experimental time and length scales using quantum-accurate, billion-atom molecular dynamics simulations with machine-learning models of interatomic interactions and employing the most powerful computers in the world. Specifically, Oleynik will focus on atomic-scale mechanisms of solid-solid and solid-liquid phase transitions of carbon and nature of inelastic deformations in diamond. These transformative simulations guide our experimental campaigns at NIF, Omega, Z, and EuXFEL facilities towards observing predicted phenomena.

SPECIAL SEMINAR

Wednesday, July 26, 2023

Time: 11:00 a.m.

Speaker: Professor Nathan Mayne, University of Exeter, UK

Topic: Exoplanet Climates in 3D Challenges & Opportunities

Host: Anjali Piette

Abstract: Planetary climates are tricky requiring a range of model complexities to understand, interpret and predict observations. Simple models aid our understanding of the key mechanisms but can provide seemingly robust inferences which are actually dependent on the physical ingredients or assumptions (e.g., 1D versus 3D), whereas higher complexity models are more resource intensive and dependent on a larger number of input parameters. Our progress in understanding the Earth's climate, and that of its neighbouring solar system planets, a relatively small number of well observed cases, is helping us accelerate our understanding of the vast (overwhelming?) diversity of exoplanets. In turn, studies of exoplanets are benefitting the understanding of our own changing climate. One lesson from Earth climate research is clear, a range of approaches and perspectives is vital to make progress.                                                                                

In this talk I will detail the research undertaken by our team at the University of Exeter employing, predominantly, 3D climate models across a range of complexities to try to unravel the interactions between chemistry, radiative transfer, dynamics and biology in planetary climates. I will focus on simulations of gas giant exoplanets, including clouds and chemical kinetics, compared to observations from JWST, and simulations of terrestrial planets, connecting the Early Earth with potentially habitable candidates. Additionally, I will briefly describe the knowledge transfer with Earth climate research through a co-development framework with the UK Met Office. Finally, I will mention the context of our work within the recent exoplanet Model Intercomparison Projects of the CUISINES framework.  

Join Tim Rehm, Physics PhD Student at Brown University, for this week's astronomy seminar. 
 

Dr. Bean will present the comparative planetology results that have emerged from JWST's first year of exoplanet atmosphere observations. The beautiful spectra that have been obtained for hot Jupiters demonstrate that these objects have diverse metallicities and C/O ratios to go along with their diverse masses and radii. On the other hand, detection of the atmospheres of terrestrial planets have so far remained elusive. In some cases strict upper limits on atmospheric thickness constrain how atmospheric loss and retention depends on key planetary and stellar properties. Dr. Bean will conclude with a look ahead at what these JWST results mean for exoplanet atmosphere characterization in the GMT era.

Abstract: Titan stands out amongst satellites in our solar system as a strangely Earth-like world, including an active precipitation cycle with liquid present at the surface. It is also noteworthy for the abundant organics coating the surface, including the equatorial dunes. Titan’s thick, nitrogen-dominated atmosphere is a critical driver of the present-day state of this planetary system, stabilizing liquid hydrocarbons, and producing organics via photochemistry. In this presentation, I will discuss the origin of Titan’s atmospheric volatiles, including nitrogen, methane, and argon. I will review evidence that supports an atmospheric contribution of as much as 50% from complex organic material similar to insoluble organic matter found in chondrites, present experimental work to test this hypothesis, and discuss broader implications for Titan’s interior and habitability.