Despite its small size, Enceladus has a wide variety of surface features, ranging from old, heavily cratered regions to young, tectonically deformed terrain.

[20] Cryovolcanoes near the south pole shoot geyser-like jets of water vapor, molecular hydrogen, other volatiles, and solid material, including sodium chloride crystals and ice particles, into space, totaling about 200 kilograms (440 pounds) per second.

[25] In 2014, NASA reported that Cassini had found evidence for a large south polar subsurface ocean of liquid water with a thickness of around 10 km (6 mi).

[30] Cassini performed chemical analysis of Enceladus's plumes, finding evidence for hydrothermal activity,[31][32] possibly driving complex chemistry.

Geological features on Enceladus are named by the International Astronomical Union (IAU) after characters and places from Richard Francis Burton's 1885 translation of The Book of One Thousand and One Nights.

[54] Analysis of the CDA and INMS data suggest that the gas cloud Cassini flew through during the July encounter, and observed from a distance with its magnetometer and UVIS, was actually a water-rich cryovolcanic plume, originating from vents near the south pole.

[56] Visual confirmation of venting came in November 2005, when Cassini imaged geyser-like jets of icy particles rising from Enceladus's south polar region.

[69] They appear to be the youngest features in this region and are surrounded by mint-green-colored (in false color, UV–green–near IR images), coarse-grained water ice, seen elsewhere on the surface within outcrops and fracture walls.

[70] Results from the visual and infrared mapping spectrometer (VIMS) instrument suggest that the green-colored material surrounding the tiger stripes is chemically distinct from the rest of the surface of Enceladus.

[6] Following Voyager's encounters with Enceladus in the early 1980s, scientists postulated it to be geologically active based on its young, reflective surface and location near the core of the E ring.

[15] Cassini flew through this gas cloud on a few encounters, allowing instruments such as the ion and neutral mass spectrometer (INMS) and the cosmic dust analyzer (CDA) to directly sample the plume.

The combined analysis of imaging, mass spectrometry, and magnetospheric data suggests that the observed south polar plume emanates from pressurized subsurface chambers, similar to Earth's geysers or fumaroles.

[76][77][78] This is consistent with geophysical calculations which predict the south polar fissures are under compression near periapsis, pushing them shut, and under tension near apoapsis, pulling them open.

[79] Strike-slip tectonics may also drive localized extension along alternating (left- and right- lateral) transtensional zones (e.g., pull-apart basins) over the Tiger Stripes, thereby regulating jet activity within these regions.

Castillo, Matson et al. (2005) suggested that Iapetus and the other icy satellites of Saturn formed relatively quickly after the formation of the Saturnian subnebula, and thus were rich in short-lived radionuclides.

Porco, Helfenstein et al. (2006) used limb measurements to determine that its shape, assuming hydrostatic equilibrium, is consistent with an undifferentiated interior, in contradiction to the geological and geochemical evidence.

[6] However, the current shape also supports the possibility that Enceladus is not in hydrostatic equilibrium, and may have rotated faster at some point in the recent past (with a differentiated interior).

[26][98] Measurements of Enceladus's "wobble" as it orbits Saturn—called libration—suggests that the entire icy crust is detached from the rocky core and therefore that a global ocean is present beneath the surface.

[113][114] The high pH is interpreted to be a consequence of serpentinization of chondritic rock that leads to the generation of H2, a geochemical source of energy that could support both abiotic and biological synthesis of organic molecules such as those that have been detected in Enceladus's plumes.

[134] The "hot start" model of heating suggests Enceladus began as ice and rock that contained rapidly decaying short-lived radioactive isotopes of aluminium, iron and manganese.

Enormous amounts of heat were then produced as these isotopes decayed for about 7 million years, resulting in the consolidation of rocky material at the core surrounded by a shell of ice.

[137] The subsurface layer heating the surface water ice could be an ammonia–water slurry at temperatures as low as 170 K (−103 °C), and thus less energy is required to produce the plume activity.

[138] Additional historical information is needed to explain how Enceladus first entered the high-energy state (e.g. more radiogenic heating or a more eccentric orbit in the past).

[159] The presence of a wide range of organic compounds and ammonia indicates their source may be similar to the water/rock reactions known to occur on Earth and that are known to support life.

[159][161] On December 14, 2023, astronomers reported the first time discovery, in the plumes of Enceladus, of hydrogen cyanide, a possible chemical essential for life as we know it, as well as other organic molecules, some of which are yet to be better identified and understood.

According to the researchers, "these [newly discovered] compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life.

The flybys have yielded significant information concerning Enceladus's surface, as well as the discovery of water vapor with traces of simple hydrocarbons venting from the geologically active south polar region.

[172] These discoveries prompted the adjustment of Cassini's flight plan to allow closer flybys of Enceladus, including an encounter in March 2008 that took it to within 48 km of the surface.

[175][176][177] On December 14, 2023, astronomers reported the first time discovery, in the plumes of Enceladus, of hydrogen cyanide, a possible chemical essential for life as we know it, as well as other organic molecules, some of which are yet to be better identified and understood.

According to the researchers, "these [newly discovered] compounds could potentially support extant microbial communities or drive complex organic synthesis leading to the origin of life.