Death of moon Chrysalis may have spawned Saturn’s rings
WASHINGTON: Call it the case of the missing moon.
Scientists using data obtained by Nasa’s Cassini spacecraft and computer simulations said yesterday the destruction of a large moon that strayed too close to Saturn would account both for the birth of the gas giant planet’s magnificent rings and its unusual orbital tilt of about 27deg.
The researchers named this hypothesised moon Chrysalis and said it may have been torn apart by tidal forces from Saturn’s gravitational pull perhaps 160 million years ago — relatively recent compared to the date of the planet’s formation more than 4.5 billion years ago.
About 99% of the Chrysalis wreckage appeared to have plunged into Saturn’s atmosphere while the remaining 1% stayed in orbit around the planet and eventually formed the large ring system that was one of the wonders of our solar system, the researchers said. They chose the name Chrysalis because it refers to a butterfly’s pupal stage before it transforms into its glorious adult form.
‘‘As a butterfly emerges from a chrysalis, the rings of Saturn emerged from the primordial satellite Chrysalis,’’ Prof Jack Wisdom said. He is a professor of planetary science at the Massachusetts Institute of Technology and lead author of the study published in the journal Science.
The researchers estimated that Chrysalis was roughly the size of Iapetus, Saturn’s thirdlargest moon that has a diameter of a little over 1470km.
‘‘We assume it was mostly composed of water ice,’’ planetary scientist and study coauthor Burkhard Militzer, of the
University of California, Berkeley, said.
Saturn’s rings, predominantly made of particles of water ice ranging from smaller than a grain of sand up to the size of a mountain, extend up to 282,000km from the planet but generally are only about 10m thick. While the solar system’s other large gas planets including Jupiter also possess rings, they are paltry compared to those of Saturn, the sixth planet from the sun.
Nearly 10 times as far from the sun as Earth, Saturn is the secondlargest planet in our solar system behind Jupiter, with a volume 750 times greater than Earth. Saturn, made up mostly of hydrogen and helium, is orbited by 83 known moons, including Titan, the solar system’s secondlargest moon — bigger than the planet Mercury.
Cassini orbited Saturn 294 times from 2004 to 2017, obtaining vital data including gravity measurements that were key to the new study, before the robotic explorer made a death plunge into the planet. — Reuters