Saturn Put A Ring On It Relatively Recently, Study Says
Saturn is famous for its lovely rings, but a new study suggests the planet has spent most of its 4.5 billion years without them. That's because the rings are likely only 10 million to 100 million years old, according to a newly published report [open, DOI: 10.1126/science.aat2965] [DX] in the journal Science that's based on findings from NASA's Cassini probe.
Cassini spent some 13 years orbiting Saturn before plunging down and slamming into its atmosphere. During its final orbits, the spacecraft dove between the planet and its rings. That let scientists measure the gravitational effect of the rings and get a good estimate of the ring material's mass.
What they found is that it's only about 40 percent of the mass of Saturn's moon Mimas, which is way smaller than Earth's moon. This small mass suggests that the rings are relatively young. That's because the rings seem to be made of extremely pure water ice, suggesting that the bright white rings have not existed long enough to be contaminated by the bombardment of messy, dirty comets that would be expected to occur over billions of years. Some scientists thought it was possible that darker debris from comets might lie beneath the bright ice, undetectable to their instruments, but this new study shows that isn't the case.
Related: Saturn's 'Ring Rain' is a Surprising Cocktail of Chemicals
Most of Saturn's Rings Could Disappear Within 100 Million Years
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https://www.sciencenews.org/article/saturn-ring-rain-surprising-cocktail-chemicals
The "ring rain" of material falling from Saturn's rings into the planet's atmosphere is a much more intense, contaminated downpour than scientists thought.
For decades, astronomers have suspected that Saturn's rings pelt the planet with grains of water ice, but some of the final observations from NASA's Cassini spacecraft provide the first detailed views of these celestial showers (SN: 4/14/18, p. 6). Ring rain is highly contaminated with organic matter and other molecules, and hammers Saturn at thousands of kilograms per second, researchers report in the Oct. 5 Science. Understanding the rain's surprising quantity and quality could help clarify the origins and evolution of Saturn's rings.
Researchers analyzed data collected by Cassini's Ion Neutral Mass Spectrometer during the spacecraft's final few orbits in 2017, as it sailed through the gap between Saturn and its innermost ring, known as the D ring (SN Online: 9/15/17). Water constituted only about 24 percent of the material tumbling from Saturn's ring system into its atmosphere; the rest was methane, carbon monoxide, dinitrogen, ammonia, carbon dioxide and fragments of organic nanoparticles.
The ring rain's diverse chemical composition "was a big surprise," because remote observations show that Saturn's ring system, on the whole, is almost entirely water ice, says Cassini project scientist Linda Spilker of NASA's Jet Propulsion Laboratory in Pasadena, Calif., who wasn't involved in the study. Researchers aren't sure why ring rain is so deprived of water.
NASA Research Reveals Saturn is Losing Its Rings at "Worst-Case-Scenario" Rate
New NASA research confirms that Saturn is losing its iconic rings at the maximum rate estimated from Voyager 1 & 2 observations made decades ago. The rings are being pulled into Saturn by gravity as a dusty rain of ice particles under the influence of Saturn's magnetic field.
"We estimate that this 'ring rain' drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn's rings in half an hour," said James O'Donoghue of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "From this alone, the entire ring system will be gone in 300 million years, but add to this the Cassini-spacecraft measured ring-material detected falling into Saturn's equator, and the rings have less than 100 million years to live. This is relatively short, compared to Saturn's age of over 4 billion years." O'Donoghue is lead author of a study on Saturn's ring rain appearing in Icarus [DOI: 10.1016/j.icarus.2018.10.027] [DX] December 17.
Scientists have long wondered if Saturn was formed with the rings or if the planet acquired them later in life. The new research favors the latter scenario, indicating that they are unlikely to be older than 100 million years, as it would take that long for the C-ring to become what it is today assuming it was once as dense as the B-ring. "We are lucky to be around to see Saturn's ring system, which appears to be in the middle of its lifetime. However, if rings are temporary, perhaps we just missed out on seeing giant ring systems of Jupiter, Uranus and Neptune, which have only thin ringlets today!" O'Donoghue added.
It's time to mine the rings.
(Score: 0) by Anonymous Coward on Saturday January 19 2019, @08:06AM
From the oort cloud, right?
(Score: 2) by JoeMerchant on Saturday January 19 2019, @01:33PM
What happens when one giant ball of ice smashes into another giant ball of ice in just the right way? 100 million years of big rings, about 2% of the life of the solar system.
Makes sense, with the smaller, thinner rings being discovered around Jupiter.
So, then, what happens when one giant ball of ice smashes into a 3 mile deep liquid water ocean? Bruce Willis to the rescue, of course.
🌻🌻 [google.com]
(Score: 0) by Anonymous Coward on Saturday January 19 2019, @02:19PM
...married.