Events

April 11, 2023 11:00 - 12:00 EDT

Ice Giant Systems Seminar Series: Dr. Chloe Beddingfield

Webinar Zoom Link

Presenter: Dr. Chloe Beddingfield (SETI Institute)
Topic: Miranda's Thick Regolith Indicates a Major Mantling Event from an Unknown Source
Abstract: We investigated "muted" craters and scarps across Miranda's cratered terrain. The morphologies of the muted craters are most consistent with modification by regolith deposition instead of erosion or viscous relaxation. We used three techniques to estimate regolith thickness. The results of our analyses indicate that Miranda has one of the thickest regolith layers in the solar system, which could have important implications for its interior thermal properties. Regolith appears to mantle some scarps within Arden, but not Elsinore or Inverness, indicating that Arden may be the oldest corona, contrary to previous relative age estimates. We propose three possible sources for Miranda's thick regolith: (1) giant impact ejecta, (2) plume deposits, and (3) Uranian ring deposits. Follow-up studies that investigate these three scenarios are required.

Registration not yet open.

Questions? jodi.berdis@jhuapl.edu

Related Documents:

• Ice Giants Seminar Series Connection Information.pdf

May 9, 2023 11:00 - 12:00 EDT

Ice Giant Systems Seminar Series: Dr. Dan Shim

Webinar Zoom Link

Presenter: Dr. Dan Shim (Arizona State University)
Topic: Exploring High-Pressure Chemistry to Unravel the Internal Structures of Uranus, Neptune, and Sub-Neptune Exoplanets
Abstract: The internal structures of planets are shaped by chemical and dynamic processes. However, the behavior of volatiles such as water and hydrogen in the presence of heavier elements like silicates and metals under high-pressure and high-temperature conditions remains poorly understood for low-density giant planets, such as Uranus, Neptune, and sub-Neptune exoplanets. To address this, we conducted high-pressure experiments exploring the chemical interactions between H2/H2O and silicates/metals. Our findings indicate that under such conditions, dense hydrogen reacts with silicate magma to produce H2O, potentially leading to the transformation of a dry hydrogen-rich planet into a water-rich one. The degree of conversion can be regulated by the activities of H2 and H2O, leading to a range of internal structures. Our experimental results, together with theoretical studies, suggest that high-pressure and high-temperature conditions promote significant mixing between silicate and water, and between metal and hydrogen, contributing to the compositional gradients in these types of planets. Our research underscores the critical role of high-pressure chemistry in understanding the internal structures and atmosphere-interior interactions in low-density giant planets.

Registration not yet open.

Questions? Jodi.Berdis@jhuapl.edu

Related Documents:

• Ice Giants Seminar Series Connection Information.pdf

June 13, 2023 11:00 - 11:00 EDT

Ice Giant Systems Seminar Series: Dr. Matt Clement

Webinar Zoom Link

Presenter: Dr. Matt Clement (JHU/APL)
Topic: The early secular evolution of the outer solar system and the present state of the Nice Model
Abstract: In the current consensus dynamical evolutionary hypothesis for the solar system, after forming in a compact configuration of circular orbits, the giant planets acquire their modern dynamical configuration through an episode of orbital instability. Over the past two decades, numerical simulations of the so-called Nice Model have been successfully leveraged to explain numerous peculiar solar system qualities. In particular, the orbital distributions of small bodies (e.g.: asteroids, Kuiper belt objects, irregular satellites and outer solar system trojans) provide strong observational constraints that no other proposed model is capable of satisfying. I will review the current state of the Nice Model, and its important role in the early formation of Uranus and Neptune. A key constraint on instability simulations comes from Jupiter's fifth eccentric eigenmode, which is an important driver of the solar system's global evolution. Starting from commonly-assumed near-circular orbits, the present-day magnitude of this mode in Jupiter's eccentricity vector is significantly outside the range of numerically generated outcomes. I will present results motivated by modern hydrodynamical simulations of the giant planets' evolution within the primordial gaseous disk that demonstrate how the modern Jupiter-Saturn system represents a typical simulation outcome when the giant planets' orbits are initially rather eccentric, and Uranus and Neptune are not fully formed when the instability occurs. Additionally, I will highlight how Uranus' regular moons cannot survive the typical series of encounters with Pluto-mass bodies and other planets that occur during the instability. This might suggest that the Nice Model instability pre-dated the final series of impacts that generated Uranus and Neptune's obliquities. Finally, I will discuss how additional constraints from the upcoming flagship mission will be crucial for revealing the nature of the accretion of Uranus, Neptune and their moons.

Registration not yet open.

Questions? Jodi.Berdis@jhuapl.edu

Related Documents:

• Ice Giants Seminar Series Connection Information.pdf