Geysers on Saturn's moon Enceladus may not come from its underground ocean

Plumes on Enceladus might be from surface ice, not its ocean.

: Researchers at Dartmouth College propose that geysers on Saturn's moon Enceladus may not come from a subsurface ocean, but rather from surface ice melting. This challenges the notion that Enceladus could support life, as deep fissures may not reach its ocean. They suggest shear heating along fissures, creating a 'mushy zone'. Hydrogen ratios in plumes might result from clathrates, not ocean sources.

Saturn's moon Enceladus has intrigued scientists since the Cassini spacecraft discovered water vapor plumes in 2005. Initially, these geysers were thought to originate from a subterranean ocean beneath the icy surface, suggesting a potential habitat for life. However, recent research conducted by a team at Dartmouth College, led by Victoria Corless, indicates that this popular hypothesis might not be accurate.

The team highlights two key issues with the underground ocean theory: the difficulty of deep fissures penetrating the thick ice shell and the ambiguous process of how water would travel through these cracks. Corless' team proposes an alternative, where melted surface ice along 'tiger fractures' or fissures generates the plumes. This finding not only questions the presence of an ocean but also challenges the moon's habitability.

Shear heating, friction-induced warmth from moving ice layers, is a potential factor in plume formation. The warmth generated by this process, coupled with the presence of salt, could form a slushy 'mushy zone' where ice partially melts. This zone, not a deep ocean, might be the source of Enceladus' water vapor eruptions.

Detailed analyses of the plume compositions show a high hydrogen-to-methane and carbon dioxide ratio, which can be attributed to clathrates, or trapped molecules within ice, rather than an oceanic source. The study suggests that hydrogen is more volatile, potentially escaping during partial melting.

The researchers stress the need for further investigations to explore the replenishment of salts, particles, and clathrates within the mushy zone. Continued studies could reshape our understanding of Enceladus and its potential for hosting life forms, shifting focus from deep oceans to surface-level phenomena.

Sources: Dartmouth College, Geophysical Research Letters, NASA Cassini data.

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