Lord of the rings: Saturn's halo may be
relatively recent trait
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[January 21, 2019]
By Will Dunham
WASHINGTON (Reuters) - Saturn's rings are
one of our solar system's magnificent sights, but may be a relatively
recent addition, according to data obtained from NASA's Cassini
spacecraft before the robotic explorer's 2017 death plunge into the
giant gas planet.
Scientists said on Thursday a calculation of the mass of the rings based
on gravitational measurements of the planet collected by Cassini
indicated they formed between 100 million and 10 million years ago in
roughly the final 2 percent of Saturn's current age.
On Earth, 100 million years ago was during the dinosaur age.
The findings challenge the notion favored by some astronomers that the
rings developed soon after Saturn formed about 4.5 billion years ago
along with the other planets including Earth. Others felt the rings were
much younger, but lacked crucial data like their mass to estimate their
"I like the rings and their fascinating dynamics, whether they are young
or old," said Sapienza University of Rome aerospace engineering
professor Luciano Iess, lead author of the study published in the
Saturn is the sixth planet from the sun and the solar system's
second-largest, after Jupiter. All of the four gas planets possess
rings, though Saturn's are the biggest and most spectacular, with a
diameter of about 175,000 miles (282,000 km). The numerous thin rings
are 99 percent ice and 1 percent silicate particles from interplanetary
Their mass turned out to be 45 percent lower than previous estimates
based on 1980s data from NASA's Voyager spacecraft. Lower mass indicates
a younger age, the researchers said, adding that the still-bright rings
would have been darkened by debris over a longer period.
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These Hubble Space Telescope images of Saturn, shown in this handout
composite photo released June 8, 2001 and captured from 1996 to
2000, depict the planet in different stages of its 29-year journey
around the sun. NASA/The Hubble Heritage Team/ Handout via
Scientists suspect the rings formed perhaps when a large icy comet
or moon ventured too close to Saturn and was shattered by
gravitational forces or moons collided in orbit. Saturn has 62 known
There may not be a more precise answer about the origin and age of
Saturn's rings "until we can get samples of ring material in our
labs to examine, and possibly date via radioactive decay," said
Cornell University astronomy professor and study co-author Phil
Data from Cassini's final orbits, diving between the planet and the
rings as fuel ran low, also provided insight into Saturn's internal
structure, including a core estimated at 15 to 18 times Earth's
mass. It also indicated that Saturn's atmospheric layers start
rotating in sync deeper into the planet compared to Jupiter.
(Reporting by Will Dunham; Editing by Sandra Maler)
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