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What are Saturn's Rings Made up of


Saturn's rings are made of billions of pieces of ice, dust and rocks. Some of these particles are as small as a grain of salt, while others are as big as houses. These chucks of rock and ice are thought to be pieces of comets, asteroids or even moons which were torn apart by the strong gravity of Saturn before they could reach the planet.

As others have already said, they are mostly water ice, with a little other stuff mixed in. We know this because of spectroscopy of the rings. They can even see that different parts of the rings show more non-water ice contamination than others. My own simulations show this can be misleading in that more dense material will tend to graviationally attract layers of less dense water ice particles that will reduce the visibility of the non-ice materials

The next question is where this material came from. Odds are that it is a combination of stuff that had been in a moon that was disrupted and comets. The exact origin scenario isn't well pinned down. We don't even know when they formed. A lot depends on the mass of Saturn's rings, which we currently don't know all that well. Gravity waves give us a very good estimate of the surface density, and hence the mass, in the places those waves form. Mostly that is the A ring. Mass estimates based on linearly scaling up mass with optical depth would indicate that the rings have a mass roughly equal to that of Mimas. However, numerical simulations show that the correlation between mass and optical depth isn't that simple. So it is possible that the rings are as much as 3x more massive than Mimas with lots of mass basically hidden in the B ring. If the rings are only the mass of Mimas, they could very well be "recent", in that they formed in the last 100 million years or so and they would almost certainly be less than a billion years old. However, if they are 3x the mass of Mimas, they have to be primordial.

It is worth noting that we should have an answer to the question of the mass of the rings before 2018. Part of the end of life mission for Cassini has it go on a highly elliptical polar orbit that will dip through the inner D ring, very near the surface of Saturn. The telemetry for the Cassini probe should be accurate enough to measure the gravitational pull of the rings during this maneuver, hence measuring the mass of the rings before Cassini plunges into the atmosphere and burns up.

The rings are named in alphabetical order according to when they were discovered. That makes it a little confusing when listing them in order from the planet. Below is a list of the main rings and gaps between them along with distances from the center of the planet and their widths.
  • The D ring is closest to the planet. It is at a distance of 66,970 – 74,490 km and has a width of 7,500 km.
  • C ring is at a distance of 74,490 – 91,980 km and has a width of 17,500 km.
  • Columbo Gap is at a distance of 77,800 km and has a width of 100 km.
  • Maxwell Gap is at a distance of 87,500 km and has a width of 270 km.
  • Bond Gap is at a distance of 88,690 – 88,720 km and has a width of 30 km.
  • Dawes Gap is at a distance of 90,200 – 90,220 km and has a width 20 km.
  • B ring is at a distance of 91,980 – 117,580 km with a width: 25,500 km.
  • The Cassini Division sits at a distance of 117,500 – 122,050 km and has a width of 4,700 km.
  • Huygens gap starts at 117,680 km and has a width of 285 km – 440 km.
  • The Herschel Gap is at a distance of 118,183 – 118,285 km with a width of 102 km.
  • Russell Gap is at a distance of 118,597 – 118,630 km and has a width of 33 km.
  • Jeffreys Gap sits at a distance of 118,931 – 118,969 km with a width of 38 km.
  • Kuiper Gap ranges from 119,403 -119,406 km giving it a width of 3 km.
  • Leplace Gap is at a distance of 119,848 – 120,086 km and a width of 238 km.
  • Bessel Gap is at 120,305 – 120,318 km with a width of 10 km.
  • Barnard Gap is at a distance of 120,305 – 120,318 km giving it a width of 3 km.
  • A ring is at a distance of 122,050 – 136,770 km with a width of 14,600 km.
  • Encke Gap sits between 133,570-133,895 km for a width of 325 km.
  • Keeler Gap is at a distance of 136,530-136,565 km with a width of 35 km.
  • The Roche Division is at 136,770 – 139,380 km for a width 2600 km.
  • F ring is begins at 140,224 km, but debate remains as to whether it is 30 or 500 km in width.
  • G ring is between 166,000 – 174,000 km and has a width of 8,000 km.
  • Finally, we get to the E ring. It is between 180,000 – 480,000 km giving it a width of 300,000 km.

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