Published: Mon, January 21, 2019
Science | By Michele Flores

Saturn's rings are a relatively new addition, NASA says

Saturn's rings are a relatively new addition, NASA says

That's according to newly published research that uses data gathered by NASA's Cassini mission before the spacecraft's destruction in September 2017. By calculating the gravity of the bands which jostled the spacecraft between them and Saturn, scientists were able to come up with the most precise estimate of the mass of the rings to date.

By estimating the mass of the rings through gravity measurements, the researchers gauged the age of the three main rings: A, B and C. It's still a mystery, though, how these icy rings formed.

Luckily, as Cassini approached the end of its life, NASA programmed it to perform 22 dives between the planet and the rings to probe Saturn's gravity field.

Before Cassini spacecraft's fatal plunge into Saturn's atmosphere, it repeatedly flew through the gas giant's rings and its cloud tops. By knowing the mass of the rings, and how much of that mass is composed of dust (about 1%), the researchers were able to calculate how long it would have taken for the rings to accumulate that much dust.

Lead researcher Luciano Iess (EE-ess) of Rome's Sapienza University says the findings are "another gift we received from this attractive mission".

Understanding the rings' age and mass is "a fundamental goal of its mission", he added. Those small changes ripple out to the chunks of ice in the rings that decorate the gas giant, causing small waves in the rings. Others thought the rings were very young and that Saturn had, at some point, captured an object from the Kuiper Belt or a comet and gradually reduced it to orbiting rubble.

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Thomas Stallard, from the U.K.'s University of Leicester, who was not involved in the study, told Newsweek the results were "striking" as it "once again confirms a startling truth, that Saturn's rings have not existed in the solar system since the planet formed, but are relatively young".

Kaspi and Galanti joined the Cassini team following their work as part of NASA's Juno science team, which had employed a similar orbit to produce the most reliable measurements yet of Jupiter's atmospheric depth. Although these estimates were also low, astronomers have always assumed that there was some hidden mass in large blocks of material that went unseen. "That turned out to be massive flows in the atmosphere at least 9,000 kilometers deep around the equatorial region".

The study says the rings respond to vibrations within the planet, "acting similarly to the seismometers used to measure movement caused by earthquakes". That may be surprising to hear considering how large they seem with a telescope, but the particles that comprise them are mostly tiny, like grains of sand (although they can be the size of boulders or even small mountains) and are widely spaced apart in certain areas.

It's a phenomena we've seen on Jupiter too, but the difference is the layers on Jupiter start synchronising and rotating together much higher in the atmosphere. Image credit: NASA / JPL-Caltech.

Cassini was launched from Florida in 1997. The radio science instrument was built by JPL and the Italian Space Agency, working with team members from the US and Italy.

Publication: Christopher Mankovich, et al., "Cassini Ring Seismology as a Probe of Saturn's Interior".

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