DIX Planetary Science Seminar

Variable Outflows and Multi-planet Systems: A Survey of Atmospheric Escape

Photoevaporative mass loss is thought to play a central role in sculpting the population of close-in exoplanets, and is potentially responsible for the creation of both the ‘evaporation valley' (a period dependent separation between rocky super-Earths and sub-Neptunes) and the lower boundary of the ‘Neptune desert' (a deficit of Neptune-sized planets on close-in orbits). However, the majority of current mass loss measurements are for larger planets, whose planet-to-stellar radius ratios are more favorable for transit studies of their atmospheres. Yet smaller Neptune and sub-Neptune-sized planets should be particularly vulnerable to atmospheric loss due to their lower gravitational potentials in comparison to their Jovian counterparts. For the past few years, we have surveyed atmospheric escape rates for Neptune and sub-Neptune planets on close-in orbits using metastable helium with Keck/NIRSPEC. We include repeated measurements of two benchmark sub-Neptunes, TOI-1430 b and GJ 1214 b, which both have previously published outflow detections, allowing us to quantify the importance of variability for predicting the atmospheric evolution of sub-Neptunes. Finally, we place our results into context with previous mass loss measurements to provide new insights into the role of atmospheric escape in sculpting the close-in exoplanet population.

Spectroscopy of Outer Solar System Small Bodies with JWST

Spectroscopy of Kuiper Belt objects by JWST has shown that CO2, CO, H2O, and organic ices are found in varying amounts on their surfaces. Interestingly, these same features are also common on the closer-in Centaurs (objects with perihelion inside of 30 AU) that are sourced from the Kuiper belt. Many of these Centaurs show no activity, despite being well inside of the sublimation lines for the ices seen on their surfaces. The story of how these various icy surfaces evolve thus remains unclear even with the wealth of new spectroscopic data, especially as the short dynamical lifetimes of Centaurs obscure their long-term evolution. To probe what effect heating and irradiation have on KBO surfaces, we examine the Saturnian irregular satellites, which are a sample of captured Kuiper Belt objects that have been at 10 AU for over 4 billion years. Saturn irregulars are both representative of the compositions of parent KBOs sourced from the excited parts of the Kuiper belt and demonstrate the effects of thermal processing of Kuiper belt surfaces at Saturnian temperatures. We present JWST NIRSpec spectroscopy of three Saturnian irregulars obtained as part of JWST Program 3716: Phoebe, Sionarq, and Albiorix, showcasing their distinct surfaces and comparing them to existing public Jupiter Trojan and Centaur spectra from JWST NIRSpec. Additionally, we show spectrophotometry of the small Uranian and Neptunian satellites taken with JWST NIRCam as part of public outreach data, contextualizing these observed 3.0 micron feature on these objects within the broader array of Kuiper belt spectra. We show this spectrophotometry as a preview for upcoming JWST NIRSpec spectroscopy of the Uranian and Neptunian small moons and irregular satellites as part of GO Program 4645 (PI: Matthew Belyakov, Co-PI: Ryleigh Davis).