One of the last acts of NASA’s Cassini spacecraft before its death plunge into Saturn’s hydrogen and helium atmosphere was to coast between the planet and its rings and let them tug it around, essentially acting as a gravity probe. The findings indicate that Saturn’s rings formed between 10 million and 100 million years ago.The findings, published January 17, 2019, in the peer-reviewed journal Science, support the hypothesis that the rings are rubble from a comet or Kuiper Belt object captured late in Saturn’s history.
Precise measurements of Cassini’s final trajectory have now allowed scientists to make the first accurate estimate of the amount of material in the planet’s rings, weighing them based on the strength of their gravitational pull.
“These measurements were only possible because Cassini flew so close to the surface in its final hours”, Burkhard Militzer said, a professor of earth and planetary science at the University of California, Berkeley.
This indicates that Saturn’s distinctive rings are a relatively recent development as ring mass is correlated with ring age, meaning that the rings are certainly less than 100 million years old and perhaps as young as 10 million years old.
Saturn formed 4.5 billion years ago, in the early years of our solar system. In fact, the rings may have formed much later than the planet itself, according to a new analysis of gravity science data from NASA’s Cassini spacecraft. A comet is believed to have got trapped by Saturn’s gravity and broke up. Rotating Layers Go Deep.
“The discovery of deeply rotating layers is a surprising revelation about the internal structure of the planet”, said Cassini project scientist Linda Spilker of NASA’s Jet Propulsion Laboratory in Pasadena, California. “The questions are what causes the more rapidly rotating part of the atmosphere to go so deep, and what does that tell us about Saturn’s interior”?
Models of the interior developed by Burkhard Militzer, a UC Berkeley professor and a co-author of the paper, indicate that it is 15 to 18 Earth masses. The estimate is that the rings have about two-fifths of the mass of Saturn’s moon Mimas, which is itself 2,000 times lighter than Earth’s moon.
Image Credits: Public Domain, created by NASA