Saturn surprises as Cassini continues its grand finale

July 24, 2017 by Preston Dyches, NASA
This mosaic combines views captured by Cassini as it made the first dive of the mission's Grand Finale on April 26, 2017, and shows details in bands and swirls in the atmosphere. Credit: NASA/JPL-Caltech/SSI/Hampton University

As NASA's Cassini spacecraft makes its unprecedented series of weekly dives between Saturn and its rings, scientists are finding—so far—that the planet's magnetic field has no discernable tilt. This surprising observation, which means the true length of Saturn's day is still unknown, is just one of several early insights from the final phase of Cassini's mission, known as the Grand Finale.

Other recent science highlights include promising hints about the structure and composition of the icy rings, along with high-resolution images of the rings and Saturn's atmosphere.

Cassini is now in the 15th of 22 weekly orbits that pass through the narrow gap between Saturn and its rings. The spacecraft began its finale on April 26 and will continue its dives until Sept. 15, when it will make a mission-ending plunge into Saturn's atmosphere.

"Cassini is performing beautifully in the final leg of its long journey," said Cassini Project Manager Earl Maize at NASA's Jet Propulsion Laboratory, Pasadena, California. "Its observations continue to surprise and delight as we squeeze out every last bit of science that we can get."

Cassini scientists are thrilled as well—and surprised in some cases—with the observations being made by the spacecraft in the finale. "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.

Recent images of features in Saturn's C ring called "plateaus" reveal a streaky texture that is very different from the textures of the regions around them. Credit: NASA/JPL-Caltech/Space Science Institute

Early Magnetic Field Analysis

Based on data collected by Cassini's magnetometer instrument, Saturn's magnetic field appears to be surprisingly well-aligned with the planet's rotation axis. The tilt is much smaller than 0.06 degrees—which is the lower limit the spacecraft's magnetometer data placed on the value prior to the start of the Grand Finale.

This observation is at odds with scientists' theoretical understanding of how magnetic fields are generated. Planetary magnetic fields are understood to require some degree of tilt to sustain currents flowing through the liquid metal deep inside the (in Saturn's case, thought to be liquid metallic hydrogen). With no tilt, the currents would eventually subside and the field would disappear.

Any tilt to the magnetic field would make the daily wobble of the planet's deep interior observable, thus revealing the true length of Saturn's day, which has so far proven elusive.

Recent images of features in Saturn's C ring called "plateaus" reveal a streaky texture that is very different from the textures of the regions around them. Credit: NASA/JPL-Caltech/Space Science Institute

"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. "We have not been able to resolve the length of day at Saturn so far, but we're still working on it."

The lack of a tilt may eventually be rectified with further data. Dougherty and her team believe some aspect of the planet's deep atmosphere might be masking the true internal . The team will continue to collect and analyze data for the remainder of the mission, including during the final plunge into Saturn.

The magnetometer data will also be evaluated in concert with Cassini's measurements of Saturn's gravity field collected during the Grand Finale. Early analysis of the gravity data collected so far shows discrepancies compared with parts of the leading models of Saturn's interior, suggesting something unexpected about the planet's structure is awaiting discovery.

This colorful spectrogram represents data collected by Cassini's Radio and Plasma Wave Science instrument as it crossed through Saturn's D ring on May 28, 2017. Credit: NASA/JPL-Caltech/University of Iowa

Sampling Saturn

In addition to its investigation of the planet's interior, Cassini has now obtained the first-ever samples of the planet's atmosphere and main rings, which promise new insights about their composition and structure. The spacecraft's cosmic dust analyzer (CDA) instrument has collected many nanometer-size particles while flying through the planet-ring gap, while its ion and neutral mass spectrometer (INMS) has sniffed the outermost atmosphere, called the exosphere.

During Cassini's first dive through the gap on April 26, the spacecraft was oriented so its large, saucer-shaped antenna would act as a shield against oncoming ring particles that might cause damage. While at first it appeared that there were essentially no particles in the gap, scientists later determined the particles there are very small and could be detected using the CDA instrument.

The cosmic dust analyzer was later allowed to peek out from behind the antenna during Cassini's third of four passes through the innermost of Saturn's main rings, the D ring, on June 29. During Cassini's first two passes through the inner D ring, the particle environment there was found to be benign. This prompted mission controllers to relax the shielding requirement for one orbit, in hopes of capturing ring particles there using CDA. As the spacecraft passed through the ring, the CDA instrument successfully captured some of the tiniest particles there, which the team expects will provide significant information about their composition.

This false-color view from NASA's Cassini spacecraft gazes toward the rings beyond Saturn's sunlit horizon, where a thin haze can be seen along the limb. Credit: NASA/JPL-Caltech/Space Science Institute

During the spacecraft's final five orbits, as well as it final plunge, the INMS instrument will obtain samples deeper down in the atmosphere. Cassini will skim through the outer atmosphere during these passes, and INMS is expected to send particularly important data on the composition of Saturn's atmosphere during the final plunge.

Amazing Images

Not to be outdone, Cassini's imaging cameras have been hard at work, returning some of the highest-resolution views of the rings and planet they have ever obtained. For example, close-up views of Saturn's C ring—which features mysterious bright bands called plateaus—reveal surprisingly different textures in neighboring sections of the ring. The plateaus appear to have a streaky texture, whereas adjacent regions appear clumpy or have no obvious structure at all. Ring scientists believe the new level of detail may shed light on why the plateaus are there, and what is different about the particles in them.

On two of Cassini's close passes over Saturn, on April 26 and June 29, the cameras captured ultra-close views of the cloudscape racing past, showing the planet from closer than ever before. Imaging scientists have combined images from these dives into two new image mosaics and a movie sequence. (Specifically, the previously released April 26 movie was updated to greatly enhance its contrast and sharpness.)

Launched in 1997, Cassini has orbited Saturn since arriving in 2004 for an up-close study of the planet, its rings and moons, and its vast magnetosphere. Cassini has made numerous dramatic discoveries, including a global ocean with indications of hydrothermal activity within the moon Enceladus, and liquid methane seas on another moon, Titan.

Explore further: Image: Saturn and rings, 7 June 2017

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cantdrive85
1.9 / 5 (9) Jul 24, 2017
This observation is at odds with scientists' theoretical understanding of how magnetic fields are generated. Planetary magnetic fields are understood to require some degree of tilt to sustain currents flowing through the liquid metal deep inside the planets (in Saturn's case, thought to be liquid metallic hydrogen). With no tilt, the currents would eventually subside and the field would disappear.

Oops! Observation doesn't jive with theory? Another in the endless parade of falsifications for the inept standard theory. One of these days they might figure out the Birkeland currents which are responsible for the hexagonal feature at the northern pole are also responsible for Saturn's rotation and it's magnetic field. Another fail for the pseudoscientific dynamo guess.
cantdrive85
1.5 / 5 (8) Jul 24, 2017
This observation is at odds with scientists' theoretical understanding of how magnetic fields are generated. Planetary magnetic fields are understood to require some degree of tilt to sustain currents flowing through the liquid metal deep inside the planets (in Saturn's case, thought to be liquid metallic hydrogen). With no tilt, the currents would eventually subside and the field would disappear.

Oops! Observation doesn't jive with theory? Another in the endless parade of falsifications for the inept standard theory. One of these days they might figure out the Birkeland currents which are responsible for the hexagonal feature at the northern pole are also responsible for Saturn's rotation and it's magnetic field. Another fail for the pseudoscientific dynamo guess.
cantdrive85
1.5 / 5 (8) Jul 24, 2017
This observation is at odds with scientists' theoretical understanding of how magnetic fields are generated. Planetary magnetic fields are understood to require some degree of tilt to sustain currents flowing through the liquid metal deep inside the planets (in Saturn's case, thought to be liquid metallic hydrogen). With no tilt, the currents would eventually subside and the field would disappear.

Oops! Observation doesn't jive with theory? Another in the endless parade of falsifications for the inept standard theory. One of these days they might figure out the Birkeland currents which are responsible for the hexagonal feature at the northern pole are also responsible for Saturn's rotation and it's magnetic field. Another fail for the pseudoscientific dynamo guess.
cantdrive85
1.6 / 5 (7) Jul 24, 2017
Oops, triple post... Not sure how although I bet an astrophysicist could come up with some wild conjecture.
FineStructureConstant
Jul 25, 2017
This comment has been removed by a moderator.
bschott
not rated yet Jul 25, 2017
This observation was predicted almost 3 years ago....just not by the mainstream.
691Boat
5 / 5 (2) Jul 25, 2017
This observation was predicted almost 3 years ago....just not by the mainstream.

Please link that paper. I would be interested in reading it.
thanks in advance!
bschott
1 / 5 (2) Jul 26, 2017
This observation was predicted almost 3 years ago....just not by the mainstream.

Please link that paper. I would be interested in reading it.
thanks in advance!

Start at time 50:40, the statement is made at 50:50. The explanation of how/why...watch all 3 videos.
https://www.youtu...gyJ0k8Kw
691Boat
4 / 5 (4) Jul 26, 2017
or perhaps the small angle was already shown (37 years ago), just not to the current precision:
http://science.sc...4429/407
bschott
not rated yet Jul 26, 2017
or perhaps the small angle was already shown (37 years ago), just not to the current precision:
http://science.sc...4429/407

Awesome....other than the apparent lack of history taught to current astrophysicists. If you have a paper from 1980: A) Why ask me for a source that is three years old? And B) why not post this yourself?
In the above the phrases "This surprising observation", " Saturn's magnetic field appears to be surprisingly well aligned with it's rotation axis", "This observation is at odds with scientists' theoretical understanding of how magnetic fields are generated", ""The tilt seems to be much smaller than we had previously estimated and quite challenging to explain", all indicate this was not known. Yet here you are with a mainstream peer reviewed paper from 1980 where it was acknowledged....1 - star means you appreciate the post right?
here you go.
691Boat
5 / 5 (2) Jul 26, 2017
Why do I ask for a source? Because I was hoping to have some theory, math, proper explanations etc. regarding the prediction that was made 34 years after it was already shown. It seemed you had something amazing to explain the extremely low angle and I was intrigued! Sorry your prediction was made 34-ish years after the first source I looked at discussed it. Not much of a prediction is it?
bschott
not rated yet Jul 27, 2017
Why do I ask for a source? Because I was hoping to have some theory, math, proper explanations etc. regarding the prediction that was made 34 years after it was already shown. It seemed you had something amazing to explain the extremely low angle and I was intrigued! Sorry your prediction was made 34-ish years after the first source I looked at discussed it. Not much of a prediction is it?

Depends on if you ask the scientists and writer behind this article or anyone familiar with your paper. One group thinks they found out something very surprising, the other have known it for 37 years...weird it would be reported above as a revelation of sorts when in fact it's apparently old news eh? So no, not much of a prediction at all...unless of course you are in the group that was surprised....
bschott
not rated yet Jul 27, 2017
It seemed you had something amazing to explain...

All I said was that it was predicted 3 years ago, so I am not too sure what seemed amazing...especially if you knew about it for as long as the paper you linked has been around. What I find amazing is that it is even older news than I thought it was and is being portrayed as revelatory....

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