Saturn’s moons and rings may be ‘vintage goods’ dating back more than 4 billion years — around the time of our solar system’s birth — according to new data from NASA’s Cassini spacecraft.
Though they are tinted on the surface from recent “pollution”, these bodies are from around the time that the planetary bodies in our neighbourhood began to form out of the protoplanetary nebula, the cloud of material still orbiting the Sun after its ignition as a star.
“Studying the Saturnian system helps us understand the chemical and physical evolution of our entire solar system,” said lead author Gianrico Filacchione, a Cassini participating scientist at Italy’s National Institute for Astrophysics, Rome.
“We know now that understanding this evolution requires not just studying a single moon or ring, but piecing together the relationships intertwining these bodies,” Mr. Filacchione said in a statement.
Data from Cassini’s visual and infrared mapping spectrometer (VIMS) have revealed how water ice and also colours 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 colouring 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 deduced 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.
The coloured patina on the ring particles and moons roughly corresponds to their location in the Saturn system.
For Saturn’s inner ring particles and moons, water-ice spray from the geyser moon Enceladus has a whitewashing effect.
Farther out, the scientists found that the surfaces of Saturn’s moons generally were redder the farther they orbited from Saturn.
Phoebe, one of Saturn’s outer moons and an object thought to originate in the far-off Kuiper Belt, seems to be shedding reddish dust that eventually rouges the surface of nearby moons, such as Hyperion and Iapetus.
A rain of meteoroids from outside the system appears to have turned some parts of the main ring system — notably the part of the main rings known as the B ring — a subtle reddish hue.
The paper was published in The Astrophysical Journal.