A view from NASA’s Cassini spacecraft shows Saturn’s northern hemisphere in 2016 as that part of the planet nears its northern hemisphere summer solstice. Image credit: NASA/JPL-Caltech/Space Science Institute
Using new data from NASA’s Cassini spacecraft, researchers believe they have solved a longstanding mystery of Solar System science: the length of a day on Saturn. It’s 10 hours, 33 minutes and 38 seconds.
The figure has eluded planetary scientists for decades, because the gas giant has no solid surface with landmarks to track as it rotates, and it has an unusual magnetic field that hides the planet’s rotation rate.
The answer, it turned out, was hidden in the rings.
During Cassini’s orbits of Saturn, instruments examined the icy, rocky rings in unprecedented detail. Christopher Mankovich, a graduate student in astronomy and astrophysics at UC Santa Cruz, California, United States, used the data to study wave patterns within the rings.
His work determined that the rings respond to vibrations within the planet itself, acting similarly to the seismometers used to measure movement caused by earthquakes. The interior of Saturn vibrates at frequencies that cause variations in its gravitational field. The rings, in turn, detect those movements in the ...