Cassini’s final close orbits of Saturn providing new data on ringed world
This illustration shows NASA’s Cassini spacecraft in orbit around Saturn. Image Credit: NASA/JPL-Caltech
New research based on data collected during the final orbits of the Cassini spacecraft represent a huge advance in our knowledge of the Saturn system. This is especially true in terms of the never-before explored region between the planet and its rings. The findings have invalidated some preconceived notions while raising new questions.
Six research teams published their findings back on October 5 in the journal Science, based on data from Cassini’s Grand Finale. When the spacecraft was running low on fuel, the mission team flew Cassini perilously close to Saturn for 22 orbits before deliberately plunging the spacecraft into the planet’s atmosphere in September of 2017.
Cassini flew where it had never been designed to fly, probing Saturn’s magnetized environment for the first time. The spacecraft flew through icy, rocky ring particles and sniffed the atmosphere in the 1,200-mile-wide (2,000-wide) gap between the rings and the planet’s cloud tops. The flight path pushed the spacecraft to its limits and demonstrated the power and versatility of its science instruments.
One of the recently-released Grand Finale scientific results was the discovery of complex organic compounds embedded in water nanograins which rain down from Saturn’s rings into it’s upper atmosphere. The composition of the organics is different from those found on both Enceladus and Titan, indicating that there at least three distinct reservoirs of organic molecules in the Saturn system.
Researchers were surprised to see what the materials in the gap between the rings and Saturn’s atmosphere looked like. While particles throughout the rings varied from large to small, the sampling in the gap yielded mostly tiny, nanometer-sized particles, like smoke, indicating that particles are being ground up by some yet-unknown process.
NASA’s Cassini mission, which has explored the ringed world since its arrival in orbit in 2004, came to an end on Sept. 15, 2017, when the spacecraft plunged into the gas giant’s atmosphere. Image Credit: Nathan Koga / SpaceFlight Insider
Saturn’s magnetic field is almost completely aligned with its spin axis. This is unlike every other planet in our Solar System that possess a magnetic field. Grand Finale data shows a magnetic-field tilt of less than 0.0095 degrees, compared to the 11 degree tilt of Earth’s magnetic field. According to everything scientists currently know about how planets generate magnetic fields, Saturn shouldn’t have one. This is a mystery that researchers will be working to solve.
Cassini flew over Saturn’s magnetic poles, directly sampling areas where radio emissions are generated. The findings more than doubled the number of direct measurements of radio sources from Saturn, one of the few non-terrestrial sites where researchers have been able to observe a radio-generation mechanism thought to operate throughout the universe.
“The scientific results from Cassini’s Grand Finale have justified the risks of flying the spacecraft through the gap between Saturn and its rings,” Cassini Project Scientist Linda Spilker stated via a NASA post.
Spilker went on to note that Saturn was discovered to not be like what scientists had expected
“Almost everything going on in that region turned out to be a surprise,” Spilker said. “That was the importance of going there, to explore a place we’d never been before. And the expedition really paid off — the data is tremendously exciting.”
Analysis of data collected by Cassini will be reviewed for years to come, helping scientists to paint a more complete picture of Saturn.
“Many mysteries remain, as we put together pieces of the puzzle,” Spilker said. “Results from Cassini’s final orbits turned out to be more interesting than we could have imagined.”
A few of the findings from Cassini’s direct sampling: complex organics rain down from Saturn’s rings; inner-ring particles take on electric charges and travel along magnetic-field lines; newly revealed electric-current system and radiation belt; and up-close measurement of Saturn’s near-zero magnetic-field tilt.
Image Credit: NASA/JPL-Caltech
Jim Sharkey
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.
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