Icy Worlds Research

Current Projects

Planetary Solution Chemistry

Brown, M. J.; Abramson, E.; Toner, J. D.; Bollengier, O.; Journaux, B.

Abstract: Aqueous solutions are key to understanding the structures and chemical histories of ice-covered ocean worlds including Europa, Ganymede, Callisto, Enceladus, Titan, Dione, Triton and Pluto. However, the thermodynamic properties of solutions and solid phases at the high pressures occurring in ocean world interiors are a neglected area of study, making it impossible to understand their interior structure and evolution. To address this gap in data and investigate the structure and evolution of ocean worlds, we propose to (1) measure the thermodynamic properties of aqueous solutions in the Na-Mg-Cl-SO₄ system at temperatures and pressures relevant to ocean worlds, (2) build numerical, predictive models using these data, and (3) apply these models in order to better predict ocean chemistry, stratification, and dynamics in ocean worlds.

The composition and habitability of Enceladus' ocean

Toner, J. D. and Catling, D. C.

Abstract: Cassini has found evidence for a subsurface ocean erupting plumes of material from Enceladus' south pole. Analyses of the plumes suggest a moderately saline, high pH ocean environment containing organics, carbon dioxide, methane, ammonia, argon, and molecular hydrogen. This composition suggests a potentially habitable environment that may be favorable for origin-of-life scenarios. The ability to sample the subsurface ocean via the plumes makes Enceladus a strong candidate for proposed missions.

Inferring the deep ocean composition from plume analyses is vital for proposed missions, and represents a gap in knowledge between proposed instrument suites and science return. Measurements of Enceladus' plume may not directly reflect the ocean composition because equilibrium and non-equilibrium processes will fractionate oceanic waters during transport to the surface. Efforts to model equilibrium and non-equilibrium fractionation processes in the plume are hindered by a lack of experimental data at low-temperatures and high salt concentrations relevant to Enceladus. To address these issues, we propose three tasks to: (1) measure low-temperature properties of gases and aqueous solutions relevant to Enceladus, (2) incorporate experimental and literature data into predictive numerical models, and (3) apply a box model to understanding the subsurface ocean and plume composition.

The outcomes of this research will address fundamental questions about Enceladus' ocean, including: (1) What do plume measurements indicate about the ocean composition? (2) What are the habitability parameters of the ocean, such as pH, salinity, water activity, and freezing temperature? Are there chemical gradients in the ocean important for life? (3) What do solid phases in the plume imply about conditions in the parent fluid? Could aqueous glasses preserve organics in Enceladus' plume? This research is also relevant for understanding aqueous solutions on other icy worlds such as Ceres, Europa, and Titan, as well as low-temperature aqueous chemistries on Earth and Mars.

Using proteome dynamics of psychrophilic bacteria to decipher metabolic strategies and protein signatures indicative of sustained life in ice

Junge, K.; Nunn, B.; Light, B.; Toner, J. D.

Abstract: Proposal Summary Liquid water is essential to life on Earth; however, most planets and moons in our solar system have surface temperatures well below the freezing point of pure water. Europa, Enceladus, Ceres, Titan, and other icy bodies are targets for astrobiological investigation. Mars is presently cold and dry, but orbital observations have identified flowing liquid water and there is abundant evidence for past habitable environments. Earth may also have undergone a series of global glaciations (Snowball Earth events) in its early history. The abundance of icy conditions in our solar system suggests that life in frozen environments may provide answers to questions about the origin, evolution, and ultimate fate of microbial cells and their biosignatures.

This research has value to upcoming space-exploration life detection missions. Identification of proteins newly synthesized in low-temperature environments, or proteins indicative of long-term ice survival, will provide biosignatures to target when exploring life in low-temperature ecosystems relevant to future exploration. In addition, understanding key metabolic strategies for long-term survival in ice will provide clues on early evolution and survival of life as Earth underwent extensive glaciation during the Neoproterozoic Era. This proposal directly addresses the goals of ROSES 2017 and the NASA Exobiology Program solicitation to address "the potential for the origin and establishment of life under conditions prevailing on other planetary bodies and basic research on the formation and retention of biosignatures under non-Earth conditions."