The Cassini probe is spending its last few weeks orbiting Saturn and it has just delivered a trove of data and images. While the images are of course stunning, the scientists are more focused on the data as it’s not what they expected.
The spacecraft has measured the magnetic field of the planet and discovered that the magnetic field has a tiny tilt, 0.06 degrees with respect to the rotation axis of the planet. This measurement challenges the established assumption that for a planet to have a strong magnetic field, there should be some degree of tilt.
This has not only left scientists scratching their heads, it has also complicated another thing researchers were trying to measure precisely: how quickly Saturn rotates on its axis.
"The tilt seems to be much smaller than we had previously estimated and quite challenging to explain," said Michele Dougherty, Cassini magnetometer investigation lead at Imperial College London, in a statement. "We have not been able to resolve the length of day at Saturn so far, but we're still working on it."
A day on Saturn is about 10 hours and 40 minutes, but its actual value remains a mystery. The rotation of the atmosphere is too imprecise to estimate the rotation of gas giants and the team were hoping to establish the true day length using the magnetic field. Unfortunately, things haven’t gone according to plan.
This measurement is an important science goal for the international team of researchers working with Cassini. Establishing the period in the magnetic field rotation can tell us about the internal structure of Saturn. This, in turn, might tell us how the planet formed.
But it’s not just puzzling news from the probe. Cassini managed to collect the first-ever samples from the planet’s atmosphere and main rings, which once analyzed will give us new insight into what they are made of.
"The data we are seeing from Cassini's Grand Finale are every bit as exciting as we hoped, although we are still deep in the process of working out what they are telling us about Saturn and its rings," said Cassini Project Scientist Linda Spilker at JPL.
Cassini performed its 15th out of 22 weekly orbits, which are part of its Grand Finale. The spacecraft has a fateful date on September 15, when it will take a final bow and dive into the ringed planet.
"Cassini is performing beautifully in the final leg of its long journey," said Cassini Project Manager Earl Maize at NASA's Jet Propulsion Laboratory in Pasadena, California. "Its observations continue to surprise and delight as we squeeze out every last bit of science that we can get."