- After analyzing new data from NASA’s Cassini spacecraft, researchers believed to have solved a longstanding mystery of solar system science: the length of a day on Saturn. It is 10 hours, 33 minutes and 38 seconds.
- It’s a figure that 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.
- Christopher Mankovich, a graduate student in astronomy and astrophysics at University of California, Santa Cruz, used the data to study wave patterns within the rings. During Cassini’s orbits of Saturn, instruments examined the icy, rocky rings in unprecedented detail.
- 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 inside of Saturn vibrates at frequencies that cause variations in its gravitational field. The rings, in turn, detect those movements in the field.
- The rotation rate of 10:33:38 that the analysis yielded is several minutes faster than previous estimates in 1981, which were based on radio signals from NASA’s Voyager spacecraft.
- The Voyager data, which estimated the day to be 10:39:23, was based on magnetic field information. Cassini used magnetic field data, too, but earlier estimates ranged from 10:36 all the way to 10:48.
- NASA’s Cassini’s mission ended in September 2017.
- The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency.
