In a 2023 analysis, researchers identified sodium phosphates in some salt-rich ice grains emitted by Saturn’s moon Enceladus. Cassini’s Cosmic Dust Analyzer recorded their mass spectra in Saturn’s E ring, which receives particles from the moon’s plume. Laboratory analogue experiments reproduced the phosphate signatures. Combining those experiments with the grain measurements, researchers inferred abundant dissolved phosphate in the subsurface ocean water supplying the plume. This inference assumes that the ensemble of salt-rich grains represents average source-water composition near the ocean surface; ocean heterogeneity or salt separation during transport could affect it. Phosphorus is essential to life on Earth, making the finding relevant to potential habitability. These chemical findings do not establish that life exists on Enceladus.

Sources: Postberg et al. (2023); NASA (2023)