Links
- Wikipedia
- Prometheus on Wikipedia
Prometheus
Details
Prometheus is a porous, elongated inner moon of Saturn that shepherds the inner edge of the planet's narrow F ring. Cassini images show its gravity drawing streamers from the ring and leaving kinks and dark channels in the material behind it.
Prometheus travels beside Saturn's narrow F ring, close enough for the moon and ring to continually reshape one another. It orbits along the ring's inner edge and acts as its principal shepherd, using repeated gravitational encounters to help confine the ring's dense core.
Cassini made that interaction visible. As Prometheus passes the ring, its gravity draws out streamers of icy material and leaves kinks, knots, and dark channels behind. The patterns change from orbit to orbit, turning the F ring into a record of the moon's recent passages rather than a fixed, uniform band.
The moon itself is an elongated, heavily cratered body with ridges and valleys. Its low density and bright surface point to a porous, ice-rich interior, while its unusual shape may preserve the result of several similar-sized bodies merging at low speed. Prometheus matters because a world only 137 kilometers long can visibly organize one of the most intricate structures around Saturn.
59.9km
Key facts
- Category
- Moons
- Object class
- Shepherd moon
- Composition
- Porous water ice
- Temperature
- 74 K surface
Scale context
Where Prometheus sits on the full axis
By size on the journey, Prometheus sits between Epimetheus and Puck. The band below compares Prometheus with nearby Shepherd moon objects so the size jump stays easy to read.
Shared physical scale
105km
Together, these objects make the size change around Prometheus easy to compare at a glance.
Sources
References for Prometheus
Measurements and descriptive context are compiled by the Scale of Space team from the references below. If you find an error, please let us know.
- Prometheus — Wikipedia
- Visual reference: Wikimedia Commons (NASA / JPL / Space Science Institute, Public domain)
Between the smallest and the largest, perspective is everything.
About
Scale of Space is a scroll-based journey through the universe, placing objects on a single logarithmic scale so you can compare size across an unbroken range.
Guides turn parts of that scale into curated essays, while focused views let you explore the same range through specific groups of objects.