Enceladus
Enceladus is a small icy moon of Saturn whose south polar fractures vent water-rich plumes from a global subsurface ocean.
Enceladus plume: A jet of water vapor, ice grains, and gases escaping from fractures near Enceladus’s south pole. The plume carries material from the subsurface ocean into space.
Subsurface ocean: A body of liquid water beneath an icy crust, isolated from a world's surface. Enceladus’s global ocean supplies much of the plume’s water.
Astrobiology: The study of life's origin, evolution, distribution, and potential beyond Earth. Enceladus offers a nearby ocean world for investigating potential habitability.
Discovery of Enceladus's plumes: The 2005 Cassini discovery that water-rich jets emerge from fractures near Enceladus’s south pole. This discovery transformed Enceladus from an icy moon into an active ocean-world target.
Enceladus ocean chemistry: The composition and chemical reactions of the liquid water beneath Enceladus’s ice shell. Plume samples reveal some ocean compounds but leave its full chemistry unknown.
Tiger stripes: Four prominent, warm fractures near Enceladus’s south pole, marked by parallel ridges and plume activity. These fractures are the main vents through which the plume emerges.
Enceladus's internal structure: The layered interior of Enceladus, including an icy shell, a global ocean, and a rocky core. Its layers determine how ocean material reaches the surface fractures.
Habitability: The capacity of an environment to support life, given suitable energy, chemistry, and conditions. Ocean water, chemical energy, and organic compounds make Enceladus a habitability target.
Cassini Cosmic Dust Analyzer: An instrument aboard Cassini that measured the composition and properties of dust grains. It found salts and silica-rich particles among grains linked to Enceladus’s ocean.
Enceladus's hydrothermal activity: Chemical and thermal interactions between water and rock inside Enceladus. Silica particles suggest hot water-rock reactions, but their extent remains uncertain.