Iapetus:
Saturn's Moon of two-faces
- Pronounced eye-AP-i-tus.
- Iapetus is an outer satellite of Saturn.
- Discovery in the 1600s.
- Diameter is 1,440 km (870 miles).
- Synchronous orbit - meaning it keeps one face to Saturn.
- One hemisphere is covered with frozen water.
- The other hemisphere is covered with blackish, rocky material.
- Dividing the hemispheres is a ragged, though sharply defined boundary.
- The orbit of Iapetus is tipped 15° from Saturn's equator.
- It passes well above and below the rings.
- A view of the rings from Iapetus would show a wide band.
- Phoebe is the only other satellite with such a view.
- Dust blown from distant, gray Phoebe may explain Iapetus' dark side.
- Phoebe follows a retrograde orbit.
- Debris dislodged by meteorites falls toward Saturn in a clockwise direction.
- This debris eventually encounters Iapetus.
- Iapetus then receives the high-speed dust on its leading side.
- The hemisphere would then be coated with dark dust.
- Any ice in the original soil may also be vaporized by the impact of the debris.
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