Pallene.space

Small inner moon of Saturn · Between Mimas and Enceladus

Pallene

Saturn XXXIII · S/2004 S 2

A smooth, five-kilometre moon that Voyager 2 may have glimpsed in 1981 — and that drags a full dust ring.

Key factsAstrophotography gear picker
Pallene at a glance
Object typeSmall inner moon of Saturn[1]
DiscoveredJune 1, 2004, Cassini Imaging Team[2]
First photographedPossibly by Voyager 2 on 23 Aug. 1981[2]
SizeMean radius ≈ 2.5 km[2]
RingPallene Ring, ≈ 2,500 km wide[1]
Cassini flybys16 Oct. 2010 (36,000 km); 14 Sept. 2011 (44,000 km)[1]
Mean distance≈ 212,300 km from Saturn[3]
Orbital period≈ 1.16 days[3]

A small inner moon

Pallene orbits between Mimas and Enceladus. Like Methone and Aegaeon, it is smooth and ellipsoidal, with a darker surface than expected.[1]

Seen in 1981?

After its 2004 discovery, Pallene was matched to a single Voyager 2 photo from 23 August 1981, once designated S/1981 S 14.[1]

A full dust ring

Cassini found a faint dust ring sharing Pallene’s orbit, about 2,500 km wide. Unlike Methone and Anthe, Pallene has a complete ring rather than an arc, because it is not in resonance.[1]

Near — but not in — resonance

Enceladus perturbs Pallene’s orbit. It was once thought to be in a 19:16 resonance with Enceladus, but is now known to be very close to, not in, resonance.[1]

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Orbit

Pallene circles Saturn every 1.16 days at about 212,300 km.[3]

Saturn Mimas (186 thousand km)Enceladus (238.4 thousand km) farthest ≈ 213.1 thousand km closest ≈ 211.5 thousand km
Top-down orbit of Pallene to scale, computed from JPL orbital elements (a ≈ 212.3 thousand km, e ≈ 0.004).[3] Mimas and Enceladus orbits shown for comparison.[3] Mean orbital elements; this moon’s orbit is almost perfectly circular and lies close to Saturn’s ring plane.

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Pallene’s 1981 cameo

How a single Voyager 2 frame was matched to a moon found 23 years later.

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Why Pallene has a ring, not an arc

Resonance makes the difference.

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Pallene and her sisters

The Alkyonides in myth and in orbit.

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Sources

  1. Pallene (moon) — Wikipedia
  2. Pallene — NASA Science
  3. Planetary Satellite Mean Elements — NASA JPL Solar System Dynamics
  4. Alcyonides — Wikipedia

Figures are rounded; where sources differ we note it. Spotted an error? Tell us.