Brines Across the Solar System is the Lunar and Planetary Institute’s (LPI’s) new multi-year conference series initiative intended to dive into brines as a planetary process, from modern to ancient brines and the technologies needed to explore them. Salty aqueous solutions (i.e., brines) are prominent across diverse planetary bodies. They are observed in the gas plumes presently erupting from Enceladus, reconstructed from precipitates on the surface of Ceres and Mars, and inferred from meteoritic samples. Understanding the mechanisms that led to the formation and preservation of these aqueous systems provides vital clues to their role in geological, geophysical, environmental, and biological processes.

The first conference in the series was Modern Brines, which was held as a virtual conference on October 25–28, 2021. The conference explored the environments where brines may presently exist, their biologic potential, and their role in ongoing and active planetary processes. Modern Brines was organized around three questions:

1. Where are brines presently available and what are their physical and chemical properties?
2. How do brines interact with and alter their environment in observable ways?
3. Can brines support life or foster prebiotic conditions?

To help facilitate these discussions, the conference included presentations from three keynote speakers. Dr. Jennifer Hanley of Lowell Observatory spoke about brine stability as it relates to environmental parameters and salt spectral features to identify these precipitates in extraterrestrial environments. Dr. Julie Castillo-Rogez of the Jet Propulsion Laboratory spoke about the role of brines in the geological evolution of icy bodies and how to identify these processes. Finally, Dr. Mary A. Voytek of NASA’s Science Mission Directorate spoke about the biologic potential of brines by exploring halophiles as a model for extraterrestrial life.

The conference also included talks from three invited speakers who exampled NASA missions and programs with important implications for brine studies. Dr. Germán Martínez of the LPI spoke about improving predictions of present-day brine formation on the surface of Mars with in situ environmental measurements. Dr. Cyril Grima of the University of Texas Institute for Geophysics presented on the upcoming Europa Clipper and its search for brine inclusions within the icy crust of Europa as constrained by Clipper’s radar instrument. Additionally, Dr. Alison Murray of the Desert Research Institute presented on the Network for Ocean Worlds, a NASA Astrobiology Research Coordination Network aimed at advancing comparative studies of Earth and other ocean worlds.

The first few days of the conference focused on presentations about brine stability and physiochemistry as constrained by laboratory experiments and terrestrial analogs. Although a lot has been learned about brines and their properties, an area identified for further research is extending our knowledge of brines, particularly multi-component solutions, and their properties to conditions directly relevant to present-day extraterrestrial environments through both laboratory and field work. The next topic discussed was in essence the geology of brines, or rather the observable interactions of these liquids with their environment. This included discussions of brine-mobilized flows on the main-belt asteroids Vesta and Ceres, as well as geochemical interactions between brines and their rocky environments, such as on Earth, Mars, and within the icy crusts of ocean worlds. Understanding the role of brines in cryovolcanic settings both on Ceres and the icy moons of the gas giants was identified as a key area for future research.

The conference wrapped up by contextualizing the discussion through an understanding of the role of brines in a biological system, as both preservers of biosignatures and supporters of extant life. Here, another area identified for further research was an improved understanding of the tolerances of life, both alone and in community, in polyextreme environments, such as the cold and salty liquids expected outside of Earth. For those who missed this inaugural meeting, presentations during the conference were recorded and are now available via the online program.

The next conference in the series, Ancient Brines, will focus on understanding the formation, location, and possible biosignatures associated with ancient brine systems and their impacts on the origin and evolution of life and climate. The conference will be held in Reno, Nevada, on September 12–15, 2022, and includes an optional one-day field trip to briny locations in the area. The abstract submission deadline is June 29, 2022. We hope to continue the conversation on the importance of brines across the solar system in Reno! Additionally, the entire conference series is being captured in a Focus Issue of the American Astronomical Society’s new Planetary Science Journal. The issue invites work resulting from the conference or manuscripts related to topics covered throughout the conference series.

— Text provided by Edgard G. Rivera-Valentín, USRA/Lunar and Planetary Institute