Saturn as an antiques shop

Saturn's rings and its satellites Dione, Rhea and Enceladus photographed by the Cassini space probe (Photo NASA/JPL/Space Science Institute)
Saturn’s rings and its satellites Dione, Rhea and Enceladus photographed by the Cassini space probe (Photo NASA/JPL/Space Science Institute)

A new analysis of the data received from NASA’s Cassini spacecraft has led to compare Saturn’s rings and satellites to a kind of antique shop where you can find items that date back to a time close to the birth of the solar system.

Gianrico Filacchione, a scientist of the Italian National Institute for Astrophysics (INAF), Rome, is the lead author of a paper published in the Astrophysical Journal, which explains how Saturn’s satellites and rings date back to more than 4 billion years ago. The Saturn system has allowed the scientists to understand the chemical and physical evolution of the whole solar system by connecting the relationships intertwining those celestial bodies.

This analysis was performed using the Visual and Infrared Mapping Spectrometer (VIMS), one of the instruments of the Cassini space probe composed of two cameras: one used to measure the visible light and another to measure the infrared one. Measuring the spectrum of the light reflected and emitted by the surfaces of the moons and the rings helps to determine their composition, temperature and structure.

Using in particular the analysis of the infrared radiation, VIMS has revealed a significant presence of water ice, too much to have been deposited by comets or in other ways in recent times. The analysis of the visible light has clarified that the colors of the rings and satellites are due to organic materials and dust present on their surface. It’s in a sense a form of pollution and this is instead relatively recent.

The color of the surface of Saturn’s satellites and rings is different depending on their location. The inner moons and rings are lighter because the geysers originated on Enceladus have a whitening effect. On the contrary, Phoebe, one of the outer satellites that may have been born in the Kuiper Belt and later captured by Saturn, spreads red dust that reaches the neighboring satellites such as Hyperion and Iapetus.

According to Bonnie Buratti, another scientist of the VIMS team who works at NASA’s Jet Propulsion Laboratory, the reddish color suggests that the small satellite Prometheus is made of materials that come from the rings. Until now, scientists had always thought satellites destroyed by Saturn’s gravity formed the rings but it could happen the other way around as well.

The scientists who are working with the Cassini mission will go on to understand the extraordinary Saturn’s system’s history better and better. That will help them better understand the entire solar system’s history.

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