Investigating Europa’s Habitability with the Europa Clipper

The habitability of Europa is a property within a system, which is driven by a multitude of physical and chemical processes and is defined by many interdependent parameters, so that its full characterization requires collaborative investigation. To explore Europa as an integrated system to yield a complete picture of its habitability, the Europa Clipper mission has three primary science objectives: (1) characterize the ice shell and ocean including their heterogeneity, properties, and the nature of surface–ice–ocean exchange; (2) characterize Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) characterize Europa’s geology including surface features and localities of high science interest. The mission will also address several cross-cutting science topics including the search for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. Synthesizing the mission’s science measurements, as well as incorporating remote observations by Earth-based observatories, the James Webb Space Telescope, and other space-based resources, to constrain Europa’s habitability, is a complex task and is guided by the mission’s Habitability Assessment Board (HAB)

Metal-free hydrogenation catalyzed by an air-stable borane: use of solvent as a frustrated Lewis base

In recent years ‘frustrated Lewis pairs’ (FLPs) have been shown to be effective metal‐free catalysts for the hydrogenation of many unsaturated substrates. Even so, limited functional‐group tolerance restricts the range of solvents in which FLP‐mediated reactions can be performed, with all FLP‐mediated hydrogenations reported to date carried out in non‐donor hydrocarbon or chlorinated solvents. Herein we report that the bulky Lewis acids B(C6Cl5)x(C6F5)3−x (x=0–3) are capable of heterolytic H2 activation in the strong‐donor solvent THF, in the absence of any additional Lewis base. This allows metal‐free catalytic hydrogenations to be performed in donor solvent media under mild conditions; these systems are particularly effective for the hydrogenation of weakly basic substrates, including the first examples of metal‐free catalytic hydrogenation of furan heterocycles. The air‐stability of the most effective borane, B(C6Cl5)(C6F5)2, makes this a practically simple reaction method

Investigating Europa’s habitability with the Europa Clipper

The habitability of Europa is a property within a system, which is driven by a multitude of physical and chemical processes and is defined by many interdependent parameters, so that its full characterization requires collaborative investigation. To explore Europa as an integrated system to yield a complete picture of its habitability, the Europa Clipper mission has three primary science objectives: (1) characterize the ice shell and ocean including their heterogeneity, properties, and the nature of surface–ice–ocean exchange; (2) characterize Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) characterize Europa’s geology including surface features and localities of high science interest. The mission will also address several cross-cutting science topics including the search for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. Synthesizing the mission’s science measurements, as well as incorporating remote observations by Earth-based observatories, the James Webb Space Telescope, and other space-based resources, to constrain Europa’s habitability, is a complex task and is guided by the mission’s Habitability Assessment Board (HAB)

Europa's Surface and Shallow Water: Ice Shell Activity and Implications for Habitability

Beneath the geologically complex ice shell of Europa, Jupiter’s innermost icy satellite, likely lies a vast, saline subsurface ocean that may hold conditions favorable for life. Key to that question is how processes in the ice shell, represented as a myriad of geologic features on the surface, facilitate material transport between the surface and subsurface ocean. The formation of the young, elliptically shaped surface disruptions, lenticulae and chaotic (chaos) terrain that range from 1000 km diameter, may represent one such process. Recent geologic analyses of the Galileo spacecraft observations suggests that both lenticulae and chaos terrain may form by reservoirs of saline liquid water emplaced as shallow as 1 km below the surface, or the so-called “shallow water” model. Lenticulae may form via the injection and freezing of liquid water sills 50 km in diameter. In this thesis, I aim to link observations and formation hypotheses to theoretical numerical models that define hypothesis tests to motivate future observations for upcoming flyby mission NASA’s Europa Clipper. To that end, I developed a multiphase, two-dimensional, finite difference model that describes the thermal and chemical evolution of saline, shallow water reservoirs after they are emplaced in Europa’s ice shell. Built on the foundations of terrestrial sea ice formation by applying the microphysical process of mushy layer development, I can track the distribution of salts within the ice shell during and after the solidification of these saline reservoirs to predict both their longevity within the ice shell and how they may be detected by future missions. I show that while the liquid water within injected sills beneath lenticulae are shorter lived than previous estimates < 140,000 years, the interpretation of their geomorphology suggests liquid water is present within the ice shell. Similarly, I show that melt lenses, owed to its origin as localized melt, are much longer-lasting, at least 175,000 years and potentially remain as a quasi-stable brine volume < 300 cubic km for 100,000s of years after. Observations have suggested the contemporary presence of liquid water in the ice shell but had not yet explicitly modeled or tested before. The solidification of injected sills and melt lenses predicts distinct chemical zoning patterns based on its chemistry and environmental factors. In particular, I show that the brines filling injected sills easily reach their eutectic concentration during solidification, regardless of chemistry, and can precipitate up to ~50% of the initial salt content, leaving behind layers of precipitated hydrated salts within the ice shell. Heterogeneous distributions of entrained salts through solidification and precipitated salt layers had also been proposed in the past, but no predictions on their extent or frequency had yet been made. Synthesizing my results, the current-best estimates of shallow water solidification and salt entrainment, I show that a number of investigations may be able to confirm the presence of liquid water in the ice shell through the lens of the Europa Clipper instrument suite. The heterogeneous distribution of salts and the presence of brines within the ice shell has significant implications for geophysical processes in the ice shell and its habitability.Ph.D