Three of Saturn's moons

The Cassini spacecraft observes three of Saturn’s moons set against the darkened night side of the planet.
Image credit: NASA/JPL-Caltech/Space Science Institute

A new analysis of data from NASA’s Cassini spacecraft suggests that Saturn’s moons and rings are gently worn vintage goods from around the time of our solar system’s birth.

Though they are tinted on the surface from recent “pollution,” these bodies date back more than 4 billion years. They are from around the time that the planetary bodies in our neighborhood began to form out of the protoplanetary nebula, the cloud of material still orbiting the sun after its ignition as a star. The paper, led by Gianrico Filacchione, a Cassini participating scientist at Italy’s National Institute for Astrophysics, Rome, has just been published online by the Astrophysical Journal.

“Studying the Saturnian system helps us understand the chemical and physical evolution of our entire solar system,” said Filacchione. “We know now that understanding this evolution requires not just studying a single moon or ring, but piecing together the relationships intertwining these bodies.”

Data from Cassini’s visual and infrared mapping spectrometer (VIMS) have revealed how water ice and also colors — which are the signs of non-water and organic materials –are distributed throughout the Saturnian system. The spectrometer’s data in the visible part of the light spectrum show that coloring on the rings and moons generally is only skin-deep.

Using its infrared range, VIMS also detected abundant water ice – too much to have been deposited by comets or other recent means. So the authors deduce that the water ices must have formed around the time of the birth of the solar system, because Saturn orbits the sun beyond the so-called “snow line.” Out beyond the snow line, in the outer solar system where Saturn resides, the environment is conducive to preserving water ice, like a deep freezer. Inside the solar system’s “snow line,” the environment is much closer to the sun’s warm glow, and ices and other volatiles dissipate more easily.

 

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