Saturn, the sixth planet from the Sun, is known for its beautiful rings, but NASA’s Cassini spacecraft has revealed that the Rings may also play a crucial role in heating the planet’s atmosphere. In particular, the discovery reveals the rings of Saturn are emitting heat due to the icy particles colliding with each other inside the planet’s magnetic field.
This surprising discovery was made using data collected by NASA’s Cassini spacecraft, which orbited Saturn between 2004 and 2017. The researchers used Cassini’s Radio and Plasma Wave Science (RPWS) instrument to measure the electrically charged particles that are present in Saturn’s magnetic field. They found that the rings were emitting energy in the form of radio waves, which suggests that they were heating up the planet’s atmosphere.
The researchers believe that the heating of Saturn’s atmosphere could also explain why the planet’s upper atmosphere is so much warmer than expected. The temperature at the top of Saturn’s atmosphere is about -270 degrees Celsius, which is colder than the surface temperature of the planet. However, the researchers found that the area directly above the rings was actually much warmer, with temperatures of around -170 degrees Celsius.
One of the reasons Saturn’s atmosphere is so warm is due to the planet’s distance from the Sun. While Saturn is approximately nine times farther from the Sun than Earth, its upper atmosphere is hotter than expected. The researchers believe that the Rings are crucial to explaining this phenomenon because they are providing energy to the planet’s atmosphere.
The exact mechanism behind this heating process is still unknown, but the researchers believe that it is due to the charged particles in Saturn’s magnetic field interacting with the icy particles in the Rings. As these particles collide with one another, they generate energy in the form of heat and radio waves, which then heats up the atmosphere above the Rings.
The discovery has significant implications for our understanding of Saturn’s atmosphere and could also have wider implications for our understanding of other planets with rings. Saturn is the only planet in our solar system with such distinctive features, and this research suggests that the Rings are also crucial to its atmosphere.
Furthermore, this research could also help us understand how planets in other solar systems heat their atmospheres. Many of the newfound exoplanets are believed to have rings, and this research suggests that these rings could also play a role in heating the planet’s atmosphere.
In conclusion, the discovery that the Rings of Saturn may help to heat up the planet’s atmosphere is a significant development in our understanding of the dynamics of the sixth planet from the Sun. While there is still much to learn about this process, this research could ultimately help us to better understand how planets form and evolve. With the help of instruments such as Cassini’s RPWS, we can continue to unravel the mysteries of the cosmos and the celestial bodies within it.
For NASA’s Saturn explorer, the end will come all too quickly.
Cassini, NASA’s explorer of Saturn, remaining life is now measured in just a few days. Coming up on September 12, just three days before NASA’s veteran Saturn explorer takes a dive into the planet’s atmosphere, the spacecraft will whip around the hazy moon Titan in a slingshot maneuver that will seal its fate.
During these final days, Cassini will take one last look around. Onboard cameras will snap pictures of Titan and its hydrocarbon lakes, Saturn’s innermost rings, the bizarre hexagon-shaped jet stream at Saturn’s north pole, and other targets. On the evening of September 14, Cassini will send this last photo album to Earth, about 1.4 billion kilometers away, and the engineers at NASA’s Jet Propulsion Laboratory in Pasadena will post them online.
After that, no more pictures will be taken. But seven other instruments will continue to gather data on the chemical composition of Saturn’s atmosphere, its gravity and magnetic fields, its innermost radiation belts, and its rings—for as long as they can. “We’ll be transmitting the science data back almost as fast as we gather it,” says Tom Burk, Cassini’s attitude control team lead.
Cassini is the most sophisticated space probe ever built. Launched in 1997 as a joint NASA/European Space Agency mission, it took seven years to journey to Saturn. It’s been orbiting the sixth planet from the sun ever since, sending back data of immense scientific value and images of magnificent beauty.
Cassini now begins one last campaign. Dubbed the Grand Finale, it will end on Sept. 15, 2017 with the probe plunging into Saturn’s atmosphere, where it will burn up. Although Saturn was visited by three spacecraft in the 1970s and 1980s, my fellow scientists and I couldn’t have imagined what the Cassini space probe would discover during its sojourn at the ringed planet when it launched 20 years ago.
A huge storm churning across the face of Saturn. At the time this image was taken, 12 weeks after the storm began, it had completely wrapped around the planet. NASA/JPL-Caltech/SSI, CC BY
A planet of dynamic change
Massive storms periodically appear in Saturn’s cloud tops, known as Great White Spots, observable by Earthbound telescopes. Cassini has a front-row seat to these events. We have discovered that just like Earth’s thunderstorms, these storms contain lightning and hail.
Cassini has been orbiting Saturn long enough to observe seasonal changes that cause variations in its weather patterns, not unlike the seasons on Earth. Periodic storms often appear in late summer in Saturn’s northern hemisphere.
In 2010, during northern springtime, an unusually early and intense storm appeared in Saturn’s cloud tops. It was a storm of such immensity that it encircled the entire planet and lasted for almost a year. It was not until the storm ate its own tail that it eventually sputtered and faded. Studying storms such as this and comparing them to similar events on other planets (think Jupiter’s Great Red Spot) help scientists better understand weather patterns throughout the solar system, even here on Earth.
Having made hundreds of orbits around Saturn, Cassini was also able to deeply investigate other features only glimpsed from Earth or earlier probes. Close encounters with Saturn’s largest moon, Titan, have allowed navigators to use the moon’s gravity to reorient the probe’s orbit so that it could swing over Saturn’s poles. Because of Saturn’s strong magnetic field, the poles are home to beautiful Aurorae, just like those of Earth and Jupiter.
Saturn’s six-sided vortex at Saturn’s north pole known as ‘the hexagon.’ This is a superposition of images taken with different filters, with different wavelengths of light assigned colors. NASA/JPL-Caltech/SSI/Hampton University, CC BY
Cassini has also confirmed the existence of a bizarre hexagon-shaped polar vortex originally glimpsed by the Voyager mission in 1981. The vortex, a mass of whirling gas much like a hurricane, is larger than the Earth and has top wind speeds of 220 mph.
Home to dozens of diverse worlds
Cassini discovered that Saturn has 45 more moons than the 17 previously known – placing the total now at 62.
The largest, Titan, is bigger than the planet Mercury. It possesses a dense nitrogen-rich atmosphere with a surface pressure one and a half times that of Earth’s. Cassini was able to probe beneath this moon’s cloud cover, discovering rivers flowing into lakes and seas and being replenished by rain. But in this case, the liquid is not water, but rather liquid methane and ethane.
False-color image of Ligeia Mare, the second largest known body of liquid on Saturn’s moon Titan. It’s filled with liquid hydrocarbons. NASA/JPL-Caltech/ASI/Cornell, CC BY
That’s not to say that water is not abundant there – but it’s so cold on Titan (with a surface temperature of -180℃) that water behaves like rock and sand. Although it has all the ingredients for life, Titan is essentially a “frozen Earth,” trapped at that moment in time before life could form.
The sixth-largest moon of Saturn, Enceladus, is an icy world about 300 miles in diameter. And for me, it’s the site of the Mission’s most spectacular finding.
The discovery started humbly, with a curious blip in magnetic field readings during the first flyby of Enceladus in 2004. As Cassini passed over the moon’s southern hemisphere, it detected strange fluctuations in Saturn’s magnetic field. From this, the Cassini magnetometer team inferred that Enceladus must be a source of ionized gas.
Intrigued, they instructed the Cassini navigators to make an even closer flyby in 2005. To our amazement, the two instruments designed to determine the composition of the gas that the spacecraft flies through, the Cassini Plasma Spectrometer (CAPS) and the Ion and Neutral Mass Spectrometer (INMS), determined that Cassini was unexpectedly passing through a cloud of ionized water. Emanating from cracks in the ice at Enceladus’ south pole, these water plumes gush into space at speeds up to 800 mph.
I am on the team that made the positive identification of water, and I have to say it was the most thrilling moment in my professional career. As far as Saturn’s moons were concerned, everyone thought all of the action would be at Titan. No one expected small, unassuming Enceladus to harbor any surprises.
Geologic activity happening in real time is quite rare in the solar system. Before Enceladus, the only known active world beyond Earth was Jupiter’s moon Io, which possesses erupting volcanoes. To find something akin to Old Faithful on a moon of Saturn was practically unimaginable. The fact that it all started with someone noticing an odd reading in the magnetic field data is a wonderful example of the serendipitous nature of discovery.
The geyser basin at the south pole of Enceladus, with its water plumes illuminated by scattered sunlight. NASA/JPL-Caltech/Space Science Institute, CC BY
The story of Enceladus only becomes more extraordinary. In 2009, the plumes were directly imaged for the first time. We now know that water from Enceladus comprises the largest component of Saturn’s magnetosphere (the area of space controlled by Saturn’s magnetic field), and the plumes are responsible for the very existence of Saturn’s vast E-ring, the second outermost ring of the planet.
More amazingly, we now know that beneath the crust of Enceladus is a global ocean of liquid saltwater and organic molecules, all being heated by hydrothermal vents on the seafloor. Detailed analysis of the plumes show they contain hydrocarbons. All this points to the possibility that Enceladus is an ocean world harboring life, right here in our solar system.
NASA at Saturn: Cassini’s Grand Finale.
When Cassini plunges into the cloud tops of Saturn later this year, it will mark the end of one of the most successful missions of discovery ever launched by humanity.
Scientists are now considering targeted missions to Titan, Enceladus or possibly both. One of the most valuable lessons one can take from Cassini is the need to continue exploring. As much as we learned from the first spacecraft to reach Saturn, nothing prepared us for what we would find with Cassini. Who knows what we will find next?
