Moon
Enceladus
Enceladus is an icy moon of Saturn whose subsurface ocean feeds plumes of vapour and ice particles. Cassini revealed an active, potentially habitable world, not a detection of life.
Overview
Identity and scale
Enceladus is a natural satellite of Saturn, discovered by William Herschel in 1789. SPICE identifies it as NAIF 602; Saturn is 699. JPL gives a mean radius of 252.10 ± 0.20 km, equivalent to a calculated mean diameter of 504.20 km. The mean density is 1.6097 ± 0.0038 g/cm³ and the gravitational parameter GM is 7.21037 ± 0.00009 km³/s². GM is not a mass in kilograms, and a bulk density alone does not determine every interior layer.
Orbit, rotation and tides
JPL's SAT441 mean elements give a semimajor axis of 238,400 km from Saturn's centre and a period of 1.370218 days, about 32.9 hours. They refer to the Laplace plane and the epoch 1 January 2000, 12:00 TDB. This is a mean description, not an ephemeris for calculating precise positions.
The moon keeps the same face turned towards Saturn. NASA describes a resonance with Dione: Enceladus makes approximately two revolutions for each one by Dione. This interaction helps maintain a slightly elliptical orbit; the associated tidal deformation contributes to internal heating. The orbital semimajor axis is not an altitude above Saturn's clouds.
A bright, active surface
Voyager showed both smooth icy regions and cratered terrain. Cassini revealed that the south pole has few craters, ice boulders and relatively warm fractures known as tiger stripes. The contrasting terrains indicate resurfacing episodes: a white, cold appearance does not imply geological inactivity.
In 2005, Cassini discovered jets of gas and ice particles. Some material feeds Saturn's E ring, while much falls back onto Enceladus. This helps keep the surface highly reflective. The plumes provide access to material from the interior without having to drill directly through the crust.
Ocean and chemistry
Interpretations of gravity measurements and the moon's small wobble support a global ocean beneath the ice. Plume samples contain water, salts, organic compounds and silica. Silica nanograins, together with other evidence, point to interaction between hot water and rock and to possible hydrothermal activity. These are observationally supported inferences, not direct images of vents on the ocean floor.
Habitability is not detected life
Liquid water, chemistry and heat make Enceladus important for studying habitability. Organic compounds are not themselves organisms and do not prove a biological origin. Ice-thickness estimates and hydrothermal models retain uncertainties. The connection between the ocean and the plumes allows these questions to be investigated, but the results described do not establish that Enceladus is inhabited.
Essential data
- Key fact
- NAIF 602
- Key fact
- 252.10 ± 0.20 km
- Key fact
- 1.6097 ± 0.0038 g/cm³
- Key fact
- 1.370218 days
- Key fact
- 238,400 km; from Saturn's centre
Physical properties
- Diameter
- 504.2
- Measurement
- 1.6097
- Measurement
- 7.21037
Orbital data
Values include their timeframe and uncertainty when available. This view does not simulate real-time positions.
- Semi-major axis
- 238400
- Parameter
- 1.370218
Dates and timeline
- Historical year
- 1789
Sources and references
- Catálogo astronómico del visualizador Catálogo astronómico del visualizador
- Enceladus - NASA Science NASA
- The Moon with the Plume - NASA Science NASA
- In Depth | Enceladus – NASA Solar System Exploration NASA
- Enceladus | Science – NASA Solar System Exploration NASA
- Enceladus Top 10 Science Highlights - NASA Science NASA
- Enceladus - NASA Science NASA
- ESA - Unusual geology seen during Enceladus fly-by European Space Agency
- Enceladus, Moon of Saturn - Solar System Exploration NASA
- APOD: 1995 November 25 - Saturn's Cleanest Moon: Enceladus - NASA Science NASA
- Page 1 of 26 Enceladus and Titan: Emerging Worlds of the Solar System European Space Agency
- Planetary Satellite Mean Elements — JPL Catálogo astronómico del visualizador
- NAIF Integer ID codes — JPL Catálogo astronómico del visualizador