Moon
Pan
Pan is Saturn’s innermost known moon, located within the Encke Gap of the A ring. Its mean radius is 14.1 km, its orbital period is 13.8 hours, and NASA describes it as a shepherd moon; Cassini images revealed a flying-saucer-like form associated with a prominent equatorial ridge.
Overview
Identity and classification
Pan is a moon, or natural satellite, of Saturn. NASA identifies it as the innermost of Saturn’s known moons. The available evidence also places it among the small inner ring moons shown with Atlas and Daphnis in Cassini image montages. This description has a limited evidentiary scope: Pan is securely identified as a Saturnian moon closely associated with the ring system, but the supplied material does not provide a complete dynamical family classification or a formal geological classification.
Location, orbit, and ring role
Pan orbits Saturn within the Encke Gap, a gap in Saturn’s A ring. NASA gives its orbital distance as 83,000 miles, or 134,000 kilometers, from Saturn, and its orbital period as 13.8 hours. It is described as a shepherd moon, meaning that its orbital presence is connected with the structure of nearby ring material. The evidence specifically states that Pan has a shepherding role connected with the Encke Gap. It does not, however, provide the quantitative gravitational mechanism, gap width, resonances, orbital eccentricity, inclination, or orbital speed. Those details should not be inferred solely from the shepherd-moon label.
Pan’s relationship with the rings is also visually documented. A NASA Saturn reference notes that Pan casts a long shadow across the A ring as equinox approaches. This observation shows that changing illumination geometry can make Pan’s interaction with the ring plane visually conspicuous. It does not provide enough information to derive an independent measurement of Pan’s relief, exact altitude, or detailed position from shadow length.
Size, shape, and observable geology
NASA reports a mean radius of 8.8 miles, equal to 14.1 kilometers. A mean radius does not imply that Pan is spherical. In fact, the highest-resolution images of Pan and Atlas revealed distinctive “flying saucer” shapes produced by prominent equatorial ridges, features NASA says are not seen on the other small Saturnian moons referenced in that comparison. For Pan, the evidence therefore connects its unusual outline with an equatorial ridge. It does not establish the ridge’s height, volume, age, composition, or formation process.
The closest cited images of Pan were acquired by Cassini on March 7, 2017. NASA describes them as raw, unprocessed images and as the closest views then obtained of the moon. Their stated scientific value was to help characterize Pan’s shape and geology. Shape and ridge information are thus grounded in direct spacecraft imaging, whereas a detailed geological history remains beyond the supplied evidence.
Composition, interior, and atmosphere
The sources provide no mineralogical composition, ice-to-rock proportion, mass, density, gravity field, porosity, temperature, or internal structure for Pan. They also provide no detection or characterization of an atmosphere, exosphere, or particle emission. It would therefore be inappropriate to state as fact physical traits sometimes associated with small ring moons when those traits are absent from the evidence. What is directly supported is Pan’s mean size, its distinctive visible geometry, and its orbital setting in the A ring.
Rotation, origin, and evolution
The 13.8-hour value supplied by NASA is an orbital period. The evidence does not specify a rotation period, pole orientation, rotational locking, or the long-term stability of the equatorial ridge. It likewise gives no discovery date or discovery circumstances for Pan, no accretion-from-ring-material hypothesis, no capture scenario, and no evolutionary reconstruction. Its proximity to ring material and its shepherding role are important observations, but they do not by themselves resolve its origin.
Exploration, scientific value, and limits
Cassini is the mission explicitly associated with the comparative ring-moon imagery and the 2017 close approach. According to NASA, its observations enabled improved characterization of Pan’s shape and geology. Pan is scientifically notable because it combines a position inside a gap of the A ring, a shepherd-moon role, and a visually unusual equatorial ridge. Open questions remain about composition, interior, rotation, origin, three-dimensional dimensions, and evolution. The supplied sources contain no conflicting numerical values: they consistently give a 14.1-km mean radius, a distance of 134,000 km, and a 13.8-hour orbit. Their central limitation is the absence of further technical measurements.
Essential data
- Key fact
- interactive_moon
- Key fact
- saturn-pan
- Key fact
- 539
Physical properties
- Diameter
- 28
- Measurement
- 0.365
- Measurement
- 0.00028
Orbital data
Values include their timeframe and uncertainty when available. This view does not simulate real-time positions.
- Semi-major axis
- 133600
- Parameter
- 0.575051
Dates and timeline
- Historical year
- 1990
Sources and references
- Saturn Facts — NASA Science NASA Science
- Catálogo astronómico del visualizador Catálogo astronómico del visualizador
- Saturn NASA
- Moons of Our Solar System NASA
- Atlas - NASA Science NASA
- The NASA atlas of the solar system | U.S. Geological Survey Compositional maps of Saturn's moon Phoebe from imaging spectroscopy | U.S. Geological Survey
- APOD: 2017 July 6 - Atlas, Daphnis, and Pan - NASA Science NASA
- Pan - NASA Science NASA
- In Depth | Pan – NASA Solar System Exploration NASA
- Saturn's Saucer Moons - NASA Science NASA
- Cassini Reveals Strange Shape of Saturn's Moon Pan - NASA Science NASA