Charting the Cosmic Shoreline with JWST

One of JWST’s four pillars of science points to finding the building blocks of life elsewhere in the universe. Planets orbiting M-dwarf stars represent our best (and only) opportunity to measure the spectrum of a potentially-habitable planet in the next decade. The quest towards habitability begins with a simple question: Does this planet have an atmosphere? Whether or not terrestrial M-dwarf planets can retain their atmospheres is a hotly debated topic, one that we hope JWST will answer by yielding unequivocal evidence of atmospheres through transmission spectroscopy observations. Understanding which M-dwarf planets have atmospheres could provide the first evidence of a Cosmic Shoreline, a universal division between planets with and without substantial atmospheres. We will present the latest findings from our large JWST Cycle 1 program (GO-1981; PIs: Stevenson & Lustig-Yaeger) in which we seek to detect the atmospheres of rocky, M-dwarf exoplanets using transmission spectroscopy. Published results include a flat spectrum of a potentially airless world and enticing spectral features that could be planetary or stellar contamination in nature. We will also report on more recent, unpublished results and share important lessons learned from this program. Finally, we will discuss how our five targets fit into the broader context of observed Cycle 1 targets and how the available information compares to Cosmic Shoreline predictions.