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EPSS Colloquium - spring-2023

From hot gas giants to temperate exo-Earths: a new era of exoplanet characterization with JWST and next-generation high-resolution spectrographs

April 11, 2023
3:30 p.m. - 4:30 p.m.
Slichter 3853

Presented By:

  • Björn Benneke - University of Montreal
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We are at the dawn of a new era for planetary astronomy. With our first big JWST results coming out and a new generation of high-resolution spectrographs going into service, our initial results leave little doubt that the upcoming decade presents a truly unique opportunity to understand planets and their atmospheres and climates in the most general way. The opportunity is no less than assessing the full diversity of planets in the universe and finally answering humanity’s millennia-old questions of “Are we alone?” and “How did we get here?”. In this colloquium, I will provide you with a first look into this new era by presenting an overview of our latest results. My discussion will include the first JWST transmission spectrum of a habitable-zone rocky world outside the solar system, our recent discovery of a tidally heated, likely volcanically active Earth-sized exoplanet, a discussion of the intriguing nature of the long-hypothesized “water-world” exoplanets, as well as the incredible complementary detail JWST and high-resolution spectrographs can provide to probe the formation, evolution, and atmospheric processes of giant planets.

Uncovering the Compositions of Sub-Neptune Exoplanets with JWST

April 18, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Anjali Piette - Carnegie Instituton for Science, EPL
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With no Solar System analogue, exoplanets larger than Earth but smaller than Neptune remain mysterious. The masses and radii of these 'sub-Neptunes' can be explained by a range of structures, from rocky interiors with hydrogen-rich atmospheres to water-rich planets. Atmospheric observations with JWST have the power to break this degeneracy by providing complementary compositional constraints. The archetypal sub-Neptune GJ1214b has recently been observed with JWST MIRI. I will present an analysis of its dayside and nightside MIRI LRS thermal emission spectra, using atmospheric retrievals to place unprecedented constraints on its atmospheric composition and aerosol properties. I will discuss these results in the context of sub-Neptune interior compositions, and will motivate future JWST observations which will allow multi-faceted constraints on this enigmatic population. In particular, sub-Neptunes which are smaller and much hotter (>2000K) than GJ1214b act as unique observational windows into the interiors of this population. With dayside temperatures above ~2000 K, these ‘lava worlds’ are expected to have atmospheres consisting of evaporated surface material. I will present new atmospheric models of these exciting targets, and discuss their observability with JWST. Current and future observations of exoplanets across the sub-Neptune regime have the potential to uncover the true natures of these exotic planets.

How similar is Venus to Earth?

April 25, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Prof. Francis Nimmo - UC Santa Cruz
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Venus and the Earth are almost identical in size and bulk composition, but appear to have followed very different evolutionary paths. Why? And how different are they really? In this talk I will focus on two aspects. One is the recent claim that Venus possesses features similar to continents on Earth, perhaps even suggesting an ancient Venusian ocean that has now vanished. The second is the viscosity structure of Venus’s mantle, and how it compares with that of the Earth. I will suggest some predictions that can be tested with observations from forthcoming Venus spacecraft missions.

Seismological Constraints on the Martian Crust from the InSight Mission

May 2, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Caroline Beghein - UCLA
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Seminar Description coming soon.

The role of water in planetary habitability

May 9, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Robin Wordsworth - Harvard University
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Because liquid water is essential to all known life, it plays a central role in modern definitions of habitability. However, the relationship between water and planetary habitability is far more subtle than is often assumed.  In the solar system, Mars provides important insights into this problem. Early in its history, Mars had abundant surface liquid water, and intermittently reducing atmospheric conditions that may have both warmed the climate and allowed prebiotic chemistry to occur the surface. However, H2O photolysis followed by net hydrogen loss to space has slowly oxidized and desiccated the planet, leaving it mostly inhospitable to life today. Terrestrial-type exoplanets around red dwarf stars likely also suffer extensive atmospheric erosion, water loss and oxidation, although many may still retain some water. Probing the surface conditions of these planets will be challenging, but the sulfur cycle should provide a powerful way to place constraints indirectly. Huge opportunities exist over the next few years to probe the links between water, redox and planetary habitability further, via a combination of in situ rover investigations at Mars and characterization of rocky exoplanets by JWST and the next generation of ground-based telescopes.

Old problems, new approach: Applications of Ensemble-Tree Machine Learning to Hydrogeology

May 16, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Dr. Kenneth Belitz - USGS
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Insights into the interaction of the deep Earth with the surface Earth system on geologic timescales

May 23, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Prof. Brenhin Keller - Dartmouth University
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Exoplanetary Atmospheres and the JWST Revolution

May 30, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Jonathan Fortney - UCSC
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In this talk I will showcase new observations of transiting planets, directly imagined planets, and brown dwarfs from the James Webb Space Telescope (JWST), along with new modeling work to understand these observations. For the first time, JWST has allowed high signal-to-noise spectra for these objects over a broad infrared wavelength range. Giant planet atmospheres appear typically metal-enriched compared to their parent stars, which provides new insight on the planet formation process. The roles of atmospheric mixing and photochemistry, which drive atmospheres away from chemical equilibrium molecular abundances, are ubiquitous in these atmospheres, as had been suggested from previous generations of atmosphere models. Lastly, I will discuss early observations of the hottest planet in the TRAPPIST-1 system of 7 Earth sized planets, a system which is targeted by many early JWST programs. All of these observations expand our phase phase of planetary atmospheric physics and chemistry, and help us place our solar system in context.

An Overview of HelioSwarm: Revealing the Nature of Turbulence in Solar Wind and Magnetotail Plasmas

June 6, 2023
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall

Presented By:

  • Harlan Spence - University of New Hampshire
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We present an overview of HelioSwarm, a NASA Medium Explorer mission concept designed to reveal the 3D, dynamic mechanisms controlling the physics of space plasma turbulence. HelioSwarm measures plasmas and magnetic fields with a novel configuration of spacecraft. Simultaneous multi-point, multi-scale measurements allow us to address two overarching science goals: 1) Reveal the 3D spatial structure and dynamics of turbulence in a weakly collisional plasma and 2) Ascertain the mutual impact of turbulence near boundaries and large-scale structures. HelioSwarm uses a "swarm" of nine spacecraft, consisting of a "hub" spacecraft and eight "node" spacecraft. The spacecraft co-orbit in a 2-week lunar resonant Earth orbit, with an apogee/perigee of ~60/11 Earth radii. Flight dynamics design and on-board propulsion produce inter-spacecraft separations ranging from 10's to 1000's km in geometries needed to distinguish between proposed models of turbulence. Each node possesses an instrument suite consisting of a Faraday cup, a fluxgate magnetometer, and a search coil magnetometer; the hub has the same instruments plus an ion electrostatic analyzer. We discuss HelioSwarm mission science, implementation, and how it will provide unprecedented views into the multiscale nature of space plasma turbulence in the solar wind and Earth’s magnetosphere.