We now know how long a day is on Saturn, well more accurately than we did thanks to Cassini.
The image above, thanks to NASA/JPL-Caltech/Space Science Institute comes from Mimas and Saturn of a couple years ago.
Here’s the story from NASA: 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, 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, ...