We began this ambitious project in 2022 by focusing on modeling efforts to answer a simple question: What is the abiotic composition of atmospheres for the most common planet in the galaxy (sub-Neptunes), and the smaller rocky planets?

We argued that one cannot understand the evolution of the atmosphere without considering its interactions with the planet underneath, or the evolution of the planet without considering the exchange with the atmosphere. A strategic combination of telescope observations, experiments, and modeling efforts is the best approach to achieve this goal, but as a starting point, we focused most of our attention in the first few years of AEThER on modeling efforts. Through modeling and with a few key experiments, we studied how a hydrogen-rich atmosphere interacts with a magma ocean. We learned how a growing planet can dramatically change as it equilibrates with its surrounding atmosphere and forms copious amounts of water. We then compared these results to the atmospheric signals seen today by the James Webb Space Telescope (JWST) for low-mass planets (a few Earth masses) which show atmospheric features, with water being the most prevalent.

But many things remain unclear. Is the water outgassed from the solid planet? Is it evidence of water’s presence on the surface? Is it water that was accreted to the planet early on, or is it endogenous, retained within the planet? These questions must be evaluated in the context of an emerging realization that the physical chemistry of silicates, metals, and hydrogen at extreme conditions are largely unfamiliar. To understand the prevalence of life in the universe, it is essential to investigate these physical and chemical interactions which ultimately set the stage for life to develop.

In recent publications on this topic, there is a common theme: To understand the water’s significance there is, as concluded by Rigby et al. (2024): “a pressing need for further experimental data and/or ab initio simulations on the solubility of volatile species in silicate melt at the physical and chemical conditions that we have shown in this study to be relevant to the magma–atmosphere interface on sub-Neptunes.” This is exactly what we will do: Experimentally investigate the fate of volatile elements, the life-essential elements, through planetary evolution. We will track how carbon, nitrogen, hydrogen, and oxygen partition and evolve through the atmosphere and the solid/molten planet, answering the question: How does the proto-envelope of a growing planet equilibrate with the interior? By focusing on the link between atmospheric chemistry and the solid planets beneath, we will lay the groundwork which is essential to discover life on exoplanets, and the prevalence of habitable environments in the universe.

NEWS