SATURN SYSTEM / SATELLITE DOSSIER

Prometheus

Prometheus is an elongated icy moon of Saturn whose gravity draws streamers and channels in the F ring.

Moon view ↗

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Artist’s impression of Prometheus

Prometheus is an elongated icy moon just inside Saturn’s F ring, where its gravity draws out changing streams and channels.

Environment ↗

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DIAMETER / EARTH0.0068×
EARTHPROMETHEUS
ATMOSPHERE
No substantial atmosphere detectedEffectively airless
SURFACE TEMPERATURE
Cold exposed surface
SURFACE PRESSURE
Effectively airless
HABITABILITYNo life detected
UNPROTECTED HUMANSNot survivable

Interior ↗

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Prometheus interiorPrometheus's internal structure is unresolved.Unresolved

Moon system ↗

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Saturn moon orbitsSelected moons, ordered outward. Orbit sizes and positions are schematic; relative periods are preserved.SATURNPANDAPHNISATLASPROMETHEUSPANDORAEPIMETHEUSJANUSMIMASENCELADUSTETHYSTELESTOCALYPSODIONEHELENERHEATITANHYPERIONIAPETUSPHOEBE

Landscape ↗

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An artist’s reconstruction of Prometheus’s irregular icy terrain. Local ridges, shallow craters and fragments are imagined from Cassini’s broad views.
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Rotation ↗

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Prometheus rotation compared with EarthThe markers follow equal elapsed time on both worlds. Equal elapsed time and sidereal rotation rates. Polar schematic: sizes, axial tilt and seasons are not shown. Illumination uses a circular mean orbit, not a live sky prediction.SAME ELAPSED TIME · POLAR SCHEMATICPROMETHEUS14.8 hoursSIDEREAL ROTATIONPrograde spinEARTH23.9 hoursSIDEREAL ROTATION≈ 24 h · solar day

Gravity ↗

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Prometheus gravityEqual launches at 2 m/s; shared metre scale; air resistance ignored.0 m200 m400 m600 mEARTH9.80 m/s²PROMETHEUS0.0058 m/s²

Orbit ↗

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Prometheus orbitElliptical orbit viewed along the orbital axis, relative to Saturn. Motion is accelerated, not a live position. Distances are center to center.SATURNPROMETHEUS≈ 139,400 km
Sources ↗
PROMETHEUS

Instrument detail

THE SKY FROM PROMETHEUS

Saturn, in perspective.

SHARED ANGULAR SCALE
Saturn compared with Luna in Earth's skyAt semimajor-axis distance, Saturn spans approximately 51.23 degrees, 98.92 times the apparent diameter of Luna at its mean distance from Earth. Both disks share one angular scale.SATURNOUR MOON≈ 0.52°
Idealized size study · full disks · decorative lighting · rings excluded
ANGULAR DIAMETER
51.23°
OUR MOON'S APPARENT DIAMETER
98.92 ×
CENTER-TO-CENTER DISTANCE
139,400 km

The viewpoint is on Prometheus’s nominal spherical surface, directly facing Saturn. The reference is Luna seen from Earth’s center at its mean distance. The reference distance is the orbit’s semimajor axis. Rounded body diameters and orbital elements set the disk sizes; terrain, phases, rings and the actual sky position are not modeled.

Explore Saturn ↗
Prometheus orbitElliptical orbit viewed along the orbital axis, relative to Saturn. Motion is accelerated, not a live position. Distances are center to center.SATURNPROMETHEUS≈ 139,400 km
ONE ORBIT0.615878 Earth days around Saturn
Closest to Saturn
139,121 km
Farthest from Saturn
139,679 km

Prometheus circles Saturn. Distances are measured between the centers of the two bodies.

This mean ellipse does not simulate the changing F-ring streamers or gravitational interactions with nearby moons.

Prometheus rotation compared with EarthThe markers follow equal elapsed time on both worlds. Equal elapsed time and sidereal rotation rates. Polar schematic: sizes, axial tilt and seasons are not shown. Illumination uses a circular mean orbit, not a live sky prediction.SAME ELAPSED TIME · POLAR SCHEMATICPROMETHEUS14.8 hoursSIDEREAL ROTATIONPrograde spinEARTH23.9 hoursSIDEREAL ROTATION≈ 24 h · solar day
Marked longitude · equal time on both worlds
ONE SIDEREAL ROTATION14.8 hours

Turning through space

Prometheus turns once in each orbit, so roughly the same hemisphere faces Saturn. The spin period is 0.615878 Earth days; this is not the interval between sunrises.

0 Earth hoursShared clock

Spin comparison only; no solar day is inferred. Sizes and starting longitudes are schematic, not live positions.

Satellite atlasMoons
Saturn moon orbitsSelected moons, ordered outward. Orbit sizes and positions are schematic; relative periods are preserved.SATURNPANDAPHNISATLASPROMETHEUSPANDORAEPIMETHEUSJANUSMIMASENCELADUSTETHYSTELESTOCALYPSODIONEHELENERHEATITANHYPERIONIAPETUSPHOEBE
FEATURED MOONS19
  1. 01Pan ↗0.575051 days
  2. 02Daphnis ↗0.59408 days
  3. 03Atlas ↗0.604602 days
  4. 04Prometheus0.615878 days
  5. 05Pandora ↗0.631369 days
  6. 06Epimetheus ↗0.697012 days
  7. 07Janus ↗0.697353 days
  8. 08Mimas ↗0.9424 days
  9. 09Enceladus ↗1.37 days
  10. 10Tethys ↗1.8878 days
  11. 11Telesto ↗1.887802 days
  12. 12Calypso ↗1.887803 days
  13. 13Dione ↗2.7369 days
  14. 14Helene ↗2.736916 days
  15. 15Rhea ↗4.5175 days
  16. 16Titan ↗15.95 days
  17. 17Hyperion ↗21.2767 days
  18. 18Iapetus ↗79.331 days
  19. 19Phoebe ↗550.3039 days

Saturn’s moon system includes hazy Titan and icy Enceladus. Methane lakes on Titan and water jets from Enceladus make these worlds compelling destinations in their own right. Saturn itself takes about 29.4 Earth years to complete an orbit.

Janus and Epimetheus share nearly the same orbital distance and exchange inner and outer positions. Their separated tracks here are schematic; this view does not simulate that exchange. Telesto and Calypso share Tethys’s orbit, roughly 60 degrees ahead and behind. Their tracks and positions are also separated schematically here; co-orbital libration is not simulated. Helene similarly shares Dione’s orbit in the leading region.

Prometheus gravityEqual launches at 2 m/s; shared metre scale; air resistance ignored.0 m200 m400 m600 mEARTH9.80 m/s²PROMETHEUS0.0058 m/s²
PROMETHEUS / EARTH GRAVITY0.00059 ×

Same push, different gravity

Both balls launch at 2 m/s, using the same height and time scales. Weaker gravity gives a higher jump and a longer time in the air. Air resistance is ignored. This idealized comparison uses constant spherical gravity GM/r²; local terrain, tides and rotation are excluded. Playback runs 58× faster for both balls.

Earth · height / airtime
0.20 m / 0.41 s
Prometheus · height / airtime
346.89 m / 693.79 s
Prometheus interiorPrometheus's internal structure is unresolved.Unresolved

Beyond the surface

Prometheus’s low density is consistent with a porous ice-rich body. The distribution of rock, ice and void space is not mapped; separate internal layers and a present-day ocean are not established.

    Artist’s impression of Prometheus

    A long, uneven body.

    Prometheus is strongly elongated, with low ridges and impact depressions across a pale icy exterior. It has fewer obvious craters than nearby Pandora, Janus and Epimetheus. The portrait follows its general shape; local landscape detail is reconstructed.

    A passing moon leaves a pattern.

    As Prometheus passes close to the F ring, its gravity draws particles into streamers and leaves channels. These structures evolve as the ring material moves onward. The orbital instrument shows the moon’s mean path, not a simulation of these particle interactions.

    An icy body with a low density.

    The adopted mass and size imply a density around 0.48 grams per cubic centimeter. Substantial internal porosity is consistent with such a low value. The distribution of ice, rock and empty space is unresolved; a layered core or ocean is not established.

    Inside the F ring.

    The mean orbital scale is about 139,400 kilometers from Saturn’s center, with a period of 0.615878 Earth days. The spin comparison uses approximate synchronous rotation, keeping broadly the same side toward Saturn. Real interactions with neighboring moons and ring particles are omitted.

    DIAMETER / EARTH0.0068×
    EARTHPROMETHEUS
    EARTH
    12,742 km
    PROMETHEUS
    86.2 km
    Mean diameters · circles share one scale

    86.2 km is the adopted volume-equivalent mean diameter. Prometheus is strongly elongated; this circle does not represent its longest dimension.

    ATMOSPHERE
    No substantial atmosphere detectedEffectively airless

    Prometheus is effectively airless. No substantial atmosphere is known to provide breathable air or surface pressure.

    SURFACE TEMPERATURE
    Cold exposed surface
    SURFACE PRESSURE
    Effectively airless
    HABITABILITYNo life detected

    No life has been detected, and a habitable environment has not been established.

    UNPROTECTED HUMANSNot survivable

    The exposed surface requires oxygen, pressure protection and thermal control.

    Planet and landscape images are artistic interpretations.

    • NASA ↗
      • Classification and orbital data
      • Rotation and internal structure constraints
      • Natural conditions and human survival
      • Landscape
    • NASA ↗
      • Parent-body diameter for the angular sky comparison
    • NASA / JPL ↗
      • GM and mean radius; spherical gravity estimate GM/r²
      • Size, physical data and atmospheric constraints
      • Interior
    • NASA / JPL ↗
      • Mean orbital dimensions; distances from parent center
      • Orbit
    • naif.jpl.nasa.gov ↗
      • Rotation model and synchronous or independent spin
    • svs.gsfc.nasa.gov ↗
      • Rings
    An artist’s reconstruction of Prometheus’s irregular icy terrain. Local ridges, shallow craters and fragments are imagined from Cassini’s broad views.

    Low ridges in icy dust

    An artist’s reconstruction of Prometheus’s irregular icy terrain. Local ridges, shallow craters and fragments are imagined from Cassini’s broad views.

    An imagined view from Prometheus. Saturn’s rings are nearly edge-on; ground detail, illumination and viewing geometry are artistic interpretations.

    Saturn above the inner ring moon

    An imagined view from Prometheus. Saturn’s rings are nearly edge-on; ground detail, illumination and viewing geometry are artistic interpretations.

    Scattered pale gray ice-rich fragments embedded in soft-looking fine debris. An artistic reconstruction of Prometheus; local detail, lighting and viewpoint are imagined.

    Dust around icy fragments

    Scattered pale gray ice-rich fragments embedded in soft-looking fine debris. An artistic reconstruction of Prometheus; local detail, lighting and viewpoint are imagined.