Category: cassini

Ultra-Close Orbits of Saturn = Ultra-Cool Scie…

On Sept. 15, 2017, our Cassini spacecraft ended its epic exploration of Saturn with a planned dive into the planet’s atmosphere–sending back new science to the very last second. The spacecraft is gone, but the science continues!

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New research emerging from the final orbits represents a huge leap forward in our understanding of the Saturn system – especially the mysterious, never-before-explored region between the planet and its rings. Some preconceived ideas are turning out to be wrong while new questions are being raised. How did they form? What holds them in place? What are they made of?

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Six teams of researchers are publishing their work Oct. 5 in the journal Science, based on findings from Cassini’s Grand Finale. That’s when, as the spacecraft was running out of fuel, the mission team steered Cassini spectacularly close to Saturn in 22 orbits before deliberately vaporizing it in a final plunge into the atmosphere in September 2017.

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Knowing Cassini’s days were numbered, its mission team went for gold. The spacecraft flew where it was never designed to fly. For the first time, it probed Saturn’s magnetized environment, flew through icy, rocky ring particles and sniffed the atmosphere in the 1,200-mile-wide (2,000-kilometer-wide) gap between the rings and the cloud tops. Not only did the engineering push the spacecraft to its limits, the new findings illustrate how powerful and agile the instruments were.

Many more Grand Finale science results are to come, but today’s highlights include:

  • Complex organic compounds embedded in water nanograins rain down from Saturn’s rings into its upper atmosphere. Scientists saw water and silicates, but they were surprised to see also methane, ammonia, carbon monoxide, nitrogen and carbon dioxide. The composition of organics is different from that found on moon Enceladus – and also different from those on moon Titan, meaning there are at least three distinct reservoirs of organic molecules in the Saturn system.
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  • For the first time, Cassini saw up close how rings interact with the planet and observed inner-ring particles and gases falling directly into the atmosphere. Some particles take on electric charges and spiral along magnetic-field lines, falling into Saturn at higher latitudes – a phenomenon known as “ring rain.” But scientists were surprised to see that others are dragged quickly into Saturn at the equator. And it’s all falling out of the rings faster than scientists thought – as much as 10,000 kg of material per second.
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  • Scientists were surprised to see what the material looks like in the gap between the rings and Saturn’s atmosphere. They knew that the particles throughout the rings ranged from large to small. They thought material in the gap would look the same. But the sampling showed mostly tiny, nanograin- and micron-sized particles, like smoke, telling us that some yet-unknown process is grinding up particles. What could it be? Future research into the final bits of data sent by Cassini may hold the answer.
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  • Saturn and its rings are even more interconnected than scientists thought. Cassini revealed a previously unknown electric current system that connects the rings to the top of Saturn’s atmosphere.
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  • Scientists discovered a new radiation belt around Saturn, close to the planet and composed of energetic particles. They found that while the belt actually intersects with the innermost ring, the ring is so tenuous that it doesn’t block the belt from forming.
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  • Unlike every other planet with a magnetic field in our Solar System, Saturn’s magnetic field is almost completely aligned with its spin axis. Think of the planet and the magnetic field as completely separate things that are both spinning. Both have the same center point, but they each have their own axis about which they spin. But for Saturn the two axes are essentially the same – no other planet does that, and we did not think it was even possible for this to happen. This new data shows a magnetic-field tilt of less than 0.0095 degrees. (Earth’s magnetic field is tilted 11 degrees from its spin axis.) According to everything scientists know about how planetary magnetic fields are generated, Saturn should not have one. It’s a mystery physicists will be working to solve.
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  • Cassini flew above Saturn’s magnetic poles, directly sampling regions where radio emissions are generated. The findings more than doubled the number of reported crossings of radio sources from the planet, one of the few non-terrestrial locations where scientists have been able to study a mechanism believed to operate throughout the universe. How are these signals generated? That’s still a mystery researchers are looking to uncover.

For the Cassini mission, the science rolling out from Grand Finale orbits confirms that the calculated risk of diving into the gap – skimming the upper atmosphere and skirting the edge of the inner rings – was worthwhile.

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Almost everything going on in that region turned out to be a surprise, which was the importance of going there, to explore a place we’d never been before. And the expedition really paid off!

Analysis of Cassini data from the spacecraft’s instruments will be ongoing for years to come, helping to paint a clearer picture of Saturn.

To read the papers published in Science, visit: URL to papers

To learn more about the ground-breaking Cassini mission and its 13 years at Saturn, visit: https://www.nasa.gov/mission_pages/cassini/main/index.html

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10 Things: Why Cassini Mattered

One year ago, on Sept. 15, 2017, NASA’s Cassini spacecraft ended
its epic exploration of Saturn with a planned dive into the planet’s
atmosphere–sending back new science to the last second. The spacecraft is
gone, but the science continues. Here are 10 reasons why Cassini mattered…

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1.
Game Changers

Cassini and ESA (European Space Agency)’s Huygens probe expanded our understanding of the
kinds of worlds where life might exist.

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2. A (Little) Like Home

At Saturn’s largest moon,
Titan, Cassini and Huygens showed us one of the most Earth-like worlds we’ve
ever encountered, with weather, climate and geology that provide new ways to
understand our home planet.

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3. A Time Machine (In a Sense)

Cassini gave us a portal to see the physical processes that likely
shaped the development of our solar system, as well as planetary systems around
other stars.

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4. The Long Run

The length of Cassini’s mission enabled us to observe weather and
seasonal changes over nearly half of a Saturn year, improving our understanding
of similar processes at Earth, and potentially those at planets around other
stars.

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5. Big Science in Small Places

Cassini revealed Saturn’s moons to be unique worlds with their own
stories to tell.

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6. Ringscape

Cassini showed us the complexity of Saturn’s rings and the
dramatic processes operating within them.

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7. Pure Exploration

Some of Cassini’s best discoveries were serendipitous. What
Cassini found at Saturn prompted scientists to rethink their understanding of
the solar system.

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8. The Right Tools for the Job

Cassini represented a staggering achievement of human and
technical complexity, finding innovative ways to use the spacecraft and its
instruments, and paving the way for future missions to explore our solar
system.

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9. Jewel of the Solar System

Cassini revealed the beauty of Saturn, its rings and moons,
inspiring our sense of wonder and enriching our sense of place in the cosmos.

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10. Much Still to Teach Us

The data returned by Cassini during its 13 years at Saturn will
continue to be studied for decades, and many new discoveries are undoubtedly
waiting to be revealed. To keep pace with what’s to come, we’ve created a new
home for the mission–and its spectacular images–at https://solarsystem.nasa.gov/cassini.

Make
sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.  

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An artist rendition of Cassini’s final plunge.

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Spooky Sounds from Across the Solar System

Soaring to the depths of our universe, gallant spacecraft roam the cosmos, snapping images of celestial wonders. Some spacecraft have instruments capable of capturing radio emissions. When scientists convert these to sound waves, the results are eerie to hear.

In time for Halloween, we’ve put together a compilation of elusive “sounds” of howling planets and whistling helium that is sure to make your skin crawl.

Listen to a few here and visit our Soundcloud for more spooky sounds. 

Cassini Ring Crossing

This eerie audio represents data collected by our Cassini spacecraft, as it crossed through the gap between Saturn and its rings on April 26, 2017, during the first dive of the mission’s Grand Finale. The instrument is able to record ring particles striking the spacecraft in its data. In the data from this dive, there is virtually no detectable peak in pops and cracks that represent ring particles striking the spacecraft. The lack of discernible pops and cracks indicates the region is largely free of small particles. 

Voyager Tsunami Waves in Interstellar Space 

Listen to this howling audio from our Voyager 1 spacecraft. Voyager 1 has experienced three “tsunami waves” in interstellar space. This kind of wave occurs as a result of a coronal mass ejection erupting from the Sun. The most recent tsunami wave that Voyager experienced began in February 2014, and may still be going. Listen to how these waves cause surrounding ionized matter to ring like a bell.

Voyager Sounds of Interstellar Space

Our Voyager 1 spacecraft captured these high-pitched, spooky sounds of interstellar space from October to November 2012 and April to May 2013.

The soundtrack reproduces the amplitude and frequency of the plasma waves as “heard” by Voyager 1. The waves detected by the instrument antennas can be simply amplified and played through a speaker. These frequencies are within the range heard by human ears.

When scientists extrapolated this line even further back in time (not shown), they deduced that Voyager 1 first encountered interstellar plasma in August 2012.

Plasma Sounds at Jupiter

Ominous sounds of plasma! Our Juno spacecraft has observed plasma wave signals from Jupiter’s ionosphere. The results in this video show an increasing plasma density as Juno descended into Jupiter’s ionosphere during its close pass by Jupiter on February 2, 2017.  

Roar of Jupiter

Juno’s Waves instrument recorded this supernatural sounding encounter with the bow shock over the course of about two hours on June 24, 2016. “Bow shock” is where the supersonic solar wind is heated and slowed by Jupiter’s magnetosphere. It is analogous to a sonic boom on Earth. The next day, June 25, 2016, the Waves instrument witnessed the crossing of the magnetopause. “Trapped continuum radiation” refers to waves trapped in a low-density cavity in Jupiter’s magnetosphere.

Visit the NASA Soundcloud for more spooky space sounds: https://soundcloud.com/nasa/sets/spookyspacesounds

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Solar System: 10 Things to Know This Week

Need some space? 

Here are 10 perspective-building images for your computer desktop and mobile device wallpaper. 

These are all real images, sent very recently by our planetary missions throughout the solar system. 

1. Our Sun

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Warm up with this view from our Solar Dynamics Observatory showing active regions on the Sun in October 2017. They were observed in a wavelength of extreme ultraviolet light that reveals plasma heated to over a million degrees. 

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2. Jupiter Up-Close

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This series of enhanced-color images shows Jupiter up close and personal, as our Juno spacecraft performed its eighth flyby of the gas giant planet on Sept. 1, 2017. 

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3. Saturn’s and Its Rings

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With this mosaic from Oct. 28, 2016, our Cassini spacecraft captured one of its last looks at Saturn and its main rings from a distance. 

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4. Gale Crater on Mars

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This look from our Curiosity Mars rover includes several geological layers in Gale crater to be examined by the mission, as well as the higher reaches of Mount Sharp beyond. The redder rocks of the foreground are part of the Murray formation. Pale gray rocks in the middle distance of the right half of the image are in the Clay Unit. A band between those terrains is “Vera Rubin Ridge,” where the rover is working currently. The view combines six images taken with the rover’s Mast Camera (Mastcam) on Jan. 24, 2017. 

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5. Sliver of Saturn

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Cassini peers toward a sliver of Saturn’s sunlit atmosphere while the icy rings stretch across the foreground as a dark band on March 31, 2017. This view looks toward the unilluminated side of the rings from about 7 degrees below the ring plane. 

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6. Dwarf Planet Ceres 

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This image of the limb of dwarf planet Ceres shows a section of the northern hemisphere, as seen by our Dawn mission. Prominently featured is Occator Crater, home of Ceres’ intriguing “bright spots.” The latest research suggests that the bright material in this crater is comprised of salts left behind after a briny liquid emerged from below. 

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7. Martian Crater

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This image from our Mars Reconnaissance Orbiter (MRO) shows a crater in the region with the most impressive known gully activity in Mars’ northern hemisphere. Gullies are active in the winter due to carbon dioxide frost, but northern winters are shorter and warmer than southern winters, so there is less frost and less gully activity. 

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8. Dynamic Storm on Jupiter

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A dynamic storm at the southern edge of Jupiter’s northern polar region dominates this Jovian cloudscape, courtesy of Juno. This storm is a long-lived anticyclonic oval named North North Temperate Little Red Spot 1. Citizen scientists Gerald Eichstädt and Seán Doran processed this image using data from the JunoCam imager. 

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9. Rings Beyond Saturn’s Sunlit Horizon 

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This false-color view from the Cassini spacecraft gazes toward the rings beyond Saturn’s sunlit horizon. Along the limb (the planet’s edge) at left can be seen a thin, detached haze. 

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10. Saturn’s Ocean-Bearing Moon Enceladus

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Saturn’s active, ocean-bearing moon Enceladus sinks behind the giant planet in a farewell portrait from Cassini. This view of Enceladus was taken by NASA’s Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back before its mission came to an end on Sept. 15, after nearly 20 years in space. 

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Applying Wallpaper:
1. Click on the screen resolution you would like to use.
2. Right-click on the image (control-click on a Mac) and select the option ‘Set the Background’ or ‘Set as Wallpaper’ (or similar).

Places to look for more of our pictures include solarsystem.nasa.gov/galleries, images.nasa.gov and www.jpl.nasa.gov/spaceimages.

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Thank you, Cassini.

Thank you, Cassini.

Cassini Mission: What’s Next?

It’s Friday, Sept. 15 and our Cassini mission has officially come to a spectacular end. The final signal from the spacecraft was received here on Earth at 7:55 a.m. EDT after a fateful plunge into Saturn’s atmosphere.

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After losing contact with Earth, the spacecraft burned up like a meteor, becoming part of the planet itself.

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Although bittersweet, Cassini’s triumphant end is the culmination of a nearly 20-year mission that overflowed with discoveries.

But, what happens now?

Mission Team and Data

Now that the spacecraft is gone, most of the team’s engineers are migrating to other planetary missions, where they will continue to contribute to the work we’re doing to explore our solar system and beyond.

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Mission scientists will keep working for the coming years to ensure that we fully understand all of the data acquired during the mission’s Grand Finale. They will carefully calibrate and study all of this data so that it can be entered into the Planetary Data System. From there, it will be accessible to future scientists for years to come.

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Even beyond that, the science data will continue to be worked on for decades, possibly more, depending on the research grants that are acquired.

Other team members, some who have spent most of their career working on the Cassini mission, will use this as an opportunity to retire.

Future Missions

In revealing that Enceladus has essentially all the ingredients needed for life, the mission energized a pivot to the exploration of “ocean worlds” that has been sweeping planetary science over the past couple of decades.

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Jupiter’s moon Europa has been a prime target for future exploration, and many lessons during Cassini’s mission are being applied in planning our Europa Clipper mission, planned for launch in the 2020s.

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The mission will orbit the giant planet, Jupiter, using gravitational assists from large moons to maneuver the spacecraft into repeated close encounters, much as Cassini has used the gravity of Titan to continually shape the spacecraft’s course.

In addition, many engineers and scientists from Cassini are serving on the new Europa Clipper mission and helping to shape its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer team are developing an extremely sensitive, next-generation version of their instrument for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will be invaluable to Europa Clipper, should plume activity be confirmed on Europa.

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In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include robotic explorers to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.

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Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent recommendations from a group of planetary scientists shows interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an potential Saturn atmospheric probe.

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A variety of potential mission concepts are discussed in a recently completed study — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.

Learn more about the Cassini mission and its Grand Finale HERE.

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Cassini Spacecraft: Top Discoveries

Our Cassini spacecraft has been exploring Saturn, its stunning rings and its strange and beautiful moons for more than a decade.

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Having expended almost every bit of the rocket propellant it carried to Saturn, operators are deliberately plunging Cassini into the planet to ensure Saturn’s moons will remain pristine for future exploration – in particular, the ice-covered, ocean-bearing moon Enceladus, but also Titan, with its intriguing pre-biotic chemistry.

Let’s take a look back at some of Cassini’s top discoveries:  

Titan

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Under its shroud of haze, Saturn’s planet-sized moon Titan hides dunes, mountains of water ice and rivers and seas of liquid methane. Of the hundreds of moons in our solar system, Titan is the only one with a dense atmosphere and large liquid reservoirs on its surface, making it in some ways more like a terrestrial planet.

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Both Earth and Titan have nitrogen-dominated atmospheres – over 95% nitrogen in Titan’s case. However, unlike Earth, Titan has very little oxygen; the rest of the atmosphere is mostly methane and traced amounts of other gases, including ethane.

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There are three large seas, all located close to the moon’s north pole, surrounded by numerous smaller lakes in the northern hemisphere. Just one large lake has been found in the southern hemisphere.

Enceladus

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The moon Enceladus conceals a global ocean of salty liquid water beneath its icy surface. Some of that water even shoots out into space, creating an immense plume!

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For decades, scientists didn’t know why Enceladus was the brightest world in the solar system, or how it related to Saturn’s E ring. Cassini found that both the fresh coating on its surface, and icy material in the E ring originate from vents connected to a global subsurface saltwater ocean that might host hydrothermal vents.

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With its global ocean, unique chemistry and internal heat, Enceladus has become a promising lead in our search for worlds where life could exist.

Iapetus

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Saturn’s two-toned moon Iapetus gets its odd coloring from reddish dust in its orbital path that is swept up and lands on the leading face of the moon.

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The most unique, and perhaps most remarkable feature discovered on Iapetus in Cassini images is a topographic ridge that coincides almost exactly with the geographic equator. The physical origin of the ridge has yet to be explained…

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It is not yet year whether the ridge is a mountain belt that has folded upward, or an extensional crack in the surface through which material from inside Iapetus erupted onto the surface and accumulated locally.

Saturn’s Rings

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Saturn’s rings are made of countless particles of ice and dust, which Saturn’s moons push and tug, creating gaps and waves.

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Scientists have never before studied the size, temperature, composition and distribution of Saturn’s rings from Saturn obit. Cassini has captured extraordinary ring-moon interactions, observed the lowest ring-temperature ever recorded at Saturn, discovered that the moon Enceladus is the source for Saturn’s E ring, and viewed the rings at equinox when sunlight strikes the rings edge-on, revealing never-before-seen ring features and details.

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Cassini also studied features in Saturn’s rings called “spokes,” which can be longer than the diameter of Earth. Scientists think they’re made of thin icy particles that are lifted by an electrostatic charge and only last a few hours.  

Auroras

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The powerful magnetic field that permeates Saturn is strange because it lines up with the planet’s poles. But just like Earth’s field, it all creates shimmering auroras.

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Auroras on Saturn occur in a process similar to Earth’s northern and southern lights. Particles from the solar wind are channeled by Saturn’s magnetic field toward the planet’s poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light.  

Turbulent Atmosphere

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Saturn’s turbulent atmosphere churns with immense storms and a striking, six-sided jet stream near its north pole.

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Saturn’s north and south poles are also each beautifully (and violently) decorated by a colossal swirling storm. Cassini got an up-close look at the north polar storm and scientists found that the storm’s eye was about 50 times wider than an Earth hurricane’s eye.

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Unlike the Earth hurricanes that are driven by warm ocean waters, Saturn’s polar vortexes aren’t actually hurricanes. They’re hurricane-like though, and even contain lightning. Cassini’s instruments have ‘heard’ lightning ever since entering Saturn orbit in 2004, in the form of radio waves. But it wasn’t until 2009 that Cassini’s cameras captured images of Saturnian lighting for the first time.

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Cassini scientists assembled a short video of it, the first video of lightning discharging on a planet other than Earth.

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Cassini’s adventure will end soon because it’s almost out of fuel. So to avoid possibly ever contaminating moons like Enceladus or Titan, on Sept. 15 it will intentionally dive into Saturn’s atmosphere.

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The spacecraft is expected to lose radio contact with Earth within about one to two minutes after beginning its decent into Saturn’s upper atmosphere. But on the way down, before contact is lost, eight of Cassini’s 12 science instruments will be operating! More details on the spacecraft’s final decent can be found HERE.

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After 20 years in space, the Cassini spacecraft is running out…

After 20 years in space, the Cassini spacecraft is running out of fuel. In 2010, Cassini began a seven-year mission extension in which the plan was to expend all of the spacecraft’s propellant exploring Saturn and its moons. This led to the Grand Finale and ends with a plunge into the planet’s atmosphere at 6:32 a.m. EDT on Friday, Sept. 15.

The spacecraft will ram through Saturn’s atmosphere at four times the speed of a re-entry vehicle entering Earth’s atmosphere, and Cassini has no heat shield. So temperatures around the spacecraft will increase by 30-to-100 times per minute, and every component of the spacecraft will disintegrate over the next couple of minutes…

Cassini’s gold-colored multi-layer insulation blankets will char and break apart, and then the spacecraft’s carbon fiber epoxy structures, such as the 11-foot (3-meter) wide high-gain antenna and the 30-foot (11-meter) long magnetometer boom, will weaken and break apart. Components mounted on the outside of the central body of the spacecraft will then break apart, followed by the leading face of the spacecraft itself.

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