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Phoenix666 [soylentnews.org] writes:

How acidic is the ocean on Saturn's icy moon Enceladus [phys.org]? It's a fundamental question to understanding if this geyser-spouting moon could support life.

Enceladus is part of a family of icy worlds, including Europa (at Jupiter) and Titan (also at Saturn), populating our outer solar system. These bodies are some of the most promising places for life because they receive tidal energy from the gas giants they orbit and some contain liquid water.

The Cassini spacecraft has been taking regular measurements of Enceladus for more than a decade to evaluate its environment. One of the key factors influencing the habitability of an environment is its chemical composition, in particular its pH. On Earth, it's possible for life to exist near the extremes of the pH scale that ranges from 0 (battery acid) to 14 (drain cleaner). Knowing the pH can help us to identify geochemical reactions that affect the habitability of an environment, because many reactions cause predictable changes in pH.
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Recently, geochemist Christopher Glein led a team that developed a new approach to estimating the pH of Enceladus' ocean using observational data of the carbonate geochemistry of plume material. This is a classic problem in geochemical studies of Earth (such as rainwater), but scientists can now solve the carbonate problem on an extraterrestrial body thanks to measurements of dissolved inorganic carbon by the Cosmic Dust Analyzer (CDA), and carbon dioxide gas by the Ion and Neutral Mass Spectrometer (INMS) onboard Cassini.

Glein's team tried to create the most comprehensive chemical model to date of the ocean by accounting for compositional constraints from both INMS and CDA, such as the salinity of the plume. Their model suggests that Enceladus has a sodium, chloride and carbonate ocean with an alkaline pH of 11 or 12, close to the equivalent of ammonia or soapy water. The estimated pH is slightly higher by 1 to 2 units than an earlier estimate based on CDA data alone, but the different modeling approaches are consistent in terms of the overall chemistry of an alkaline ocean.

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