Animation of Iapetus briefly blocking a distant bright object. (NASA/JPL-Caltech/SSI. Assembled by Jason Major.)
It’s a cosmic cover-up! No, don’t put your tinfoil* hats on, this isn’t a conspiracy — it’s just Saturn’s moon Iapetus drifting in front of the bright star Gamma Orionis (aka Bellatrix) captured on Cassini’s narrow-angle camera on August 10, 2013.
Such an event is called an occultation, a term used in astronomy whenever light from one object is blocked by another — specifically when something visually larger moves in front of something apparently smaller. (The word occult means to hide or conceal… nothing mystical implied!)
The animation above was assembled from 19 raw images publicly available on the JPL Cassini mission site, stacked in Photoshop and exported as a gif. They’ve been rotated 90º from the originals but otherwise they’re right from Cassini’s camera.
Iapetus, seen above as just a thin crescent, is best known for its two-toned appearance. One half of the 914-mile-wide moon is bright and icy, the other coated with a layer of dark reddish material, giving it a real “yin-yang” appearance. (Ok, I guess that’s a little mystical. But purely coincidental.)
The Tao of Iapetus (NASA/JPL-Caltech/SSI)
It’s thought that the dark material originates from a more distant moon, Phoebe, which is being pelted by micrometeorites and shedding its surface out into orbit around Saturn, which eventually gets scooped up by the backwards-orbiting Iapetus.
The difference in albedo affects how Iapetus absorbs solar radiation too, causing the water ice beneath the darker material to evaporate over the course of its 79-Earth-day rotation and migrate around its surface, creating a sort of positive feedback loop.
While neat to look at, occultations are important to science because they provide a way to briefly peer into a world’s atmosphere (or in a small moon’s case, exosphere). Watching how light behaves as it passes behind the limb of a planet or moon lets researchers learn details of the air around it — however tenuous — pretty much for free… no probes or flybys needed!
The occulted star above is Bellatrix, the 1.6-magnitude star that marks Orion’s left shoulder.
Iapetus orbits Saturn at the considerable distance of 2,212,889 miles (3,561,300 km). Learn more about Iapetus here, and as always you can find more fantastic Cassini images from Carolyn Porco’s team at the Space Science Institute in Boulder, Colorado at the CICLOPS site here.
Dramatic plumes, both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus. Credit: NASA/JPL/SSI.
The geyser jets of Enceladus don’t shoot out in a continuous stream, but are more like an adjustable garden hose nozzle, says Cassini scientist Matt Hedman, author of a new paper about the inner workings of this fascinating tiger-striped moon. Observations from Cassini has found that the bright plume emanating from Enceladus’ south pole varies predictably. The fluctuating factor appears to be how far or close Enceladus is to its home planet, Saturn.
Scientists have hypothesized that the intensity of the jets likely varied over time, but until now had not been able to show they changed in a recognizable pattern. Hedman and colleagues were able to see the changes by examining infrared data of the plume as a whole, obtained by Cassini’s visual and infrared mapping spectrometer (VIMS), and looking at data gathered since 2004 when Cassini entered Saturn’s orbit. In 2005, the jets that form the plumes were discovered.
“The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water,” said Christophe Sotin, a co-author and Cassini team member. “Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present.”
This set of images from NASA’s Cassini mission shows how the gravitational pull of Saturn affects the amount of spray coming from jets at the active moon Enceladus. Enceladus has the most spray when it is farthest away from Saturn in its orbit (inset image on the left) and the least spray when it is closest to Saturn (inset image on the right). Credit: NASA/JPL-Caltech/University of Arizona/Cornell/SSI.
The scientists say this new finding adds to evidence that a liquid water reservoir or ocean lurks under the icy surface of the moon. This is the first clear observation the bright plume emanating from Enceladus’ south pole varies predictably. The findings were published in a scientific paper in this week’s edition of Nature.
The VIMS instrument, which enables the analysis of a wide range of data including the hydrocarbon composition of the surface of another Saturnian moon, Titan, and the seismological signs of Saturn’s vibrations in its rings, collected more than 200 images of the Enceladus plume from 2005 to 2012.
These data show the plume was dimmest when the moon was at the closest point in its orbit to Saturn. The plume gradually brightened until Enceladus was at the most distant point, where it was three to four times brighter than the dimmest detection. This is comparable to moving from a dim hallway into a brightly lit office.
Adding the brightness data to previous models of how Saturn squeezes Enceladus, the scientists deduced the stronger gravitational squeeze near the planet reduces the opening of the tiger stripes and the amount of material spraying out. They think the relaxing of Saturn’s gravity farther away from planet allows the tiger stripes to be more open and for the spray to escape in larger quantities.
“Cassini’s time at Saturn has shown us how active and kaleidoscopic this planet, its rings and its moons are,” said Linda Spilker, Cassini project scientist at JPL. “We’ve come a long way from the placid-looking Saturn that Galileo first spied through his telescope. We hope to learn more about the forces at work here as a microcosm for how our Solar System formed.”
Enceladus has likely been subject to other gravitational forces over time as well. Previous studies have shown that over hundreds of millions of years, an existing gravitational interaction between Enceladus and another moon, Dione, has caused the orbit of Enceladus to grow increasingly more elongated, or eccentric.
In turn, this produced much more tidal stress in the past and scientists think that contributed to the wide-scale fracturing and friction within Enceladus’ icy crust. The friction leads to melting of internal ice and produces an ocean and eruptions of water and organics on the surface.
Guillermo Abramson from Argentina takes a picture of himself waving at Saturn on July 19, 2013 during 'The Day the Earth Smiled' event. Credit and copyright: Guillermo Abramson.
For all our astrophotographer friends out there: If you haven’t heard about the Saturn Mosaic Project, you’ll want to take note of this. In cooperation with Astronomers Without Borders, the special project for the recent Cassini image of planet Earth, called The Day The Earth Smiled (TDTES) is sponsoring a Saturn Mosaic project, where you can submit an image you’ve taken of Saturn. Those received will be compiled into a mosaic that will look like image that Cassini took on July 19, showing Earth just below Saturn’s rings (see below). But when you zoom in you’ll see all the pictures from Earth that the mosaic is made of.
I received a note from AWB President Mike Simmons saying they need more submissions, and the deadline for submitting a photo has been extended to July 29, 2013.
“I know a lot more people will want to be a part of this if they know about it,” Mike said via email. “It’s something to tide everyone over and keep the buzz going while we wait for the final mosaic from Cassini.”
But you don’t have to be a seasoned astrophotographer to take part in the Saturn Mosaic. The image you submit doesn’t have to be one taken with a large telescope – just take a picture of Saturn as a “star” in the sky with an ordinary camera, capturing your surroundings as well. Or it could be an image you took earlier this year.
“There are other kinds of photos that anyone can submit that don’t even requiring imaging the sky,” Simmons added. “We didn’t want to limit this to only those with the ability and weather to image Saturn itself. Photos of outreach events or people waving at Saturn from JPL’s Wave at Saturn are good, too. Or just a portrait taken with the Lord of the Rings — a live view projected from a telescope or even a photo. Like a couple getting married at the time Cassini was taking their photo (and everyone else’s) posed with Saturn. I took the easy way and took a shot of me and Saturn in my office.”
These can be taken any time, so people can still take a shot and get into the mosaic (the image does need to have been taken in 2013, however.)
“It’s all about sharing and commemorating the excitement of the moment when the photo was taken, and the anticipation of the release of Cassini’s historic photos,” Simmons said. “Like all Astronomers Without Borders project, it’s open to everyone on Earth. And beyond.”
For a slide show of some of the great shots people have submitted so far, visit the Saturn Mosaic Project page to see things like Saturn with a T-Rex, outreach in Iran, kids drawings of Saturn in Ghana, and more.
Simmons said The World at Night will create the final mosaic, which is expected to be online and ready to view and zoom in on by August 4 or earlier.
The Day the Earth Smiled: Sneak Preview. In this rare image taken on July 19, 2013, the wide-angle camera on NASA’s Cassini spacecraft has captured Saturn’s rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute
The Day the Earth Smiled: Sneak Preview. In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute
The Day the Earth Smiled: Sneak Preview
In this rare image taken on July 19, 2013, the wide-angle camera on NASA’s Cassini spacecraft has captured Saturn’s rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute
See below our wider context mosaic of the Earth, Saturn and its majestic rings[/caption]
Breathtaking raw images of the Earth and Saturn system snapped by NASA’s Cassini spacecraft on July 19 during the worldwide ‘Wave at Saturn’ campaign are streaming back across 1 billion miles of interplanetary space.
Science team members are now busily processing the images to create individual color composites and a panoramic view of the ‘pale blue dot’ and the entire Saturnian system.
NASA just released the first individual color composite focusing on Earth – see above. And its spectacular!
See below our preliminary mosaic showing the Earth in context with nearly half of Saturn and floating in between its incomparably majestic rings.
Partial context mosaic of the Earth and Saturn taken by NASA’s Cassini orbiter on July 19, 2013. This mosaic was assembled from five wide angle camera raw images and offers a sneak peek of the complete panorama. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
To capture all of Saturn and its wide swath of rings, Cassini’s wide angle camera snapped a mosaic of 33 footprints.
“At each footprint, images were taken in different spectral filters for a total of 323 images,” says Carolyn Porco, Cassini Imaging Team leader of the Space Science Institute in Boulder, Colo.
Cassini took the pictures of Earth between 2:27 and 2:42 p.m. PDT on Friday, July 19 from a distance of about 898 million miles (1.44 billion kilometers) away from the home to every human being that has ever lived.
The images show the Earth and the Moon as dots barely about a pixel wide but do reveal the ‘pale blue dot’ that is home to all of humanity and our whitish colored neighbor.
Distant views of the Earth from our robotic explorers, especially from the outer reaches of our Solar System, are few and far between, and are therefore events for space and astronomy enthusiasts and everyone else to savor.
“One of the most exciting Cassini events in 2013 will be the unusual opportunity on July 19 to image the whole Saturn system as it is backlit by the sun,” explained Linda Spilker, Cassini project scientist of NASA’s Jet Propulsion Laboratory, Pasadena, Calif.
“With Saturn covering the harsh light of the sun, we will be gathering unique ring science and also catching a glimpse of our very own home planet.”
Cassini previously took an absolutely fabulous mosaic of Saturn and Earth back in 2006 that stands as one of the landmark images of the space age.
Besides being picturesque, such mosaics also serve science. For example, the 2006 image “revealed that the dusty E ring, which is fed by the water-ice plume of the moon Enceladus, had unexpectedly large variations in brightness and color around its orbit,” says Spilker.
“We’ll want to see how that looks seven Earth years and a Saturnian season later, giving us clues to the forces at work in the Saturn system. We’ll do this analysis by collecting data from our visual and infrared mapping spectrometer, composite infrared mapping spectrometer and ultraviolet imaging spectrograph in addition to the imaging cameras.”
This simulated view from NASA’s Cassini spacecraft shows the expected positions of Saturn and Earth on July 19, 2013, around the time Cassini will take Earth’s picture. Cassini will be about 898 million miles (1.44 billion kilometers) away from Earth at the time. That distance is nearly 10 times the distance from the sun to Earth. Image credit: NASA/JPL-Caltech
“July 19 marked the first time people on Earth had advance notice their planet’s portrait was being taken from interplanetary distances,” says NASA.
I waved fondly at Saturn and hope you had the chance to wave at Saturn from all across the globe. NASA reports that nearly 20,000 participated in organized events. Countless others waved too.
Cassini was launched in 1997 and achieved orbit at Saturn in 2004. The mission is scheduled to continue until 2017 when it will commit a suicide death dive into the gas giant.
“We can’t see individual continents or people in this portrait of Earth, but this pale blue dot is a succinct summary of who we were on July 19,” said Spilker in a NASA statement.
“Cassini’s picture reminds us how tiny our home planet is in the vastness of space, and also testifies to the ingenuity of the citizens of this tiny planet to send a robotic spacecraft so far away from home to study Saturn and take a look-back photo of Earth.”
JPL Waves at Saturn
As NASA’s Cassini spacecraft turned its imaging cameras to Earth, scientists, engineers and visitors at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., gathered to wave at our robotic photographer in the Saturn system on July 19, 2013. Credit: NASA/JPL-Caltech
Earth and Moon imaged from Cassini on July 19, 2013
Did you smile and wave at Saturn on Friday? If you did (and even if you didn’t) here’s how you — and everyone else on Earth — looked to the Cassini spacecraft, 898.4 million miles away.
Hope you didn’t blink!
The image above is a color-composite made from raw images acquired by Cassini in red, green, and blue visible light wavelengths. Some of the specks around the edges are background stars, and others are the result of high-energy particle noise, of which some have been digitally removed.
The Moon is the bright dot just below and to the left of Earth. (An original raw image can be seen here.)
Cassini acquired the images while capturing views of Saturn in eclipse against the Sun between 22:24:00 UTC on July 19 and 02:43:00 UTC on July 20 (6:24 to 10:43 pm EDT July 19.) On Cassini time, the Earth imaging took place between 22:47:13 UTC (6:47:13 pm EDT) and 23:01:56 UTC (7:01:56 pm EDT) on the 19th.
Full mosaic arrangement acquired by Cassini on July 19-20 UTC. Earth was positioned just below the planet. (NASA/JPL-Caltech/SSI)
The world was invited to “Wave at Saturn” beginning 5:27 pm EDT on Friday — which allowed enough time for the photons from a waving world to actually reach Cassini’s camera just beyond Saturn, 1.44 billion kilometers away. (Did you wave? I did!) It was the first time Earth’s population was made aware beforehand that their picture would be taken from such a cosmic distance.
A crowd gathered on the mall at NASA’s Jet Propulsion Laboratory in Pasadena to wave at Saturn on July 19 (NASA/JPL-Caltech)
The image of our planet and moon, seen as merely a couple of bright points of light against the blackness of space, recalls Sagan’s poignant “pale blue dot” passage from Cosmos…
“From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Consider again that dot. That’s here, that’s home, that’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
The “pale blue dot” of Earth captured by Voyager 1 in Feb. 1990 (NASA/JPL)
The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.
Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.
The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.
It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.”
— Carl Sagan (1934–1996)
A full mosaic of Cassini’s imaging of Saturn silhouetted against the Sun is expected in the coming weeks.
UPDATE: Here’s another RGB color composite, made from raw images acquired with Cassini’s wide-angle camera. It shows a view of Saturn and the rings in eclipse as seen from below and behind, backlit by the Sun. Earth is the bright point light near the center. (See original here.)
Raw image (RGB composite) of Saturn in eclipse with Earth in the distance — just a pale blue dot. (NASA/JPL-Caltech/SSI. Composite by J. Major.)
Images: NASA/JPL-Caltech/Space Science Institute. Composites by Jason Major.
Just one of the many images from Cassini used to make up "Around Saturn"
In honor of this today’s Wave at Saturn and The Day the Earth Smiled events, celebrating images to be taken of Earth from Saturn, here’s a wonderful movie showing highlights from Cassini’s exploration of the giant planet, its magnificent rings, and fascinating family of moons.
Assembled by Fabio Di Donato in memory of astrophysicist, author and activist Margherita Hack, who passed away June 29 at the age of 91, this video is an impressive tour of the Saturnian system — and a truly stunning tribute as well.
“She made me love the stars,” Fabio wrote.
This video shows a selection from more than 200,000 pictures taken by the Cassini spacecraft around Saturn’s rings in a period between 2005 and 2013. RAW images were processed to PNG thanks to the Vicar-to-PNG procedure provided by Jessica McKellar.
The music is Jazz Suite No.2: VI Waltz 2 by Shostakovich, performed by the Armonie Symphony Orchestra.
As always, you can see the latest images and news from the Cassini mission here, and find out how your photo is going to be taken from 900 million miles away (and also 60 million miles away from Mercury!) here.
Video: Fabio Di Donato. Original images: NASA/JPL-Caltech/SSI.
P.S.: Want to get a personalized certificate saying you “Waved at Saturn?” Click here.
Saturn's rings. Credit: NASA/JPL/Space Science Institute.
It’s been 9 years (to the day, in fact) since the Cassini spacecraft first entered orbit around Saturn and ever since it has been sending a steady stream of incredible images from the ringed planet back to Earth, bridging the 900-million-mile distance with countlesswonders and groundbreaking discoveries. The views Cassini has provided us of Saturn and its family of moons are unparalleled and unprecedented, but something one could remain in want of is the element of motion: Cassini’s cameras are designed to capture still images, not true video, and thus most of our best views of Saturn are static shots.
That’s where filmmaker Stephen van Vuuren and his current project, “In Saturn’s Rings,” comes in.
An award-winning filmmaker, musician, and photographer (and self-confessed übergeek) from South Africa, Stephen van Vuuren has spent the last several years compiling hundreds of thousands of images acquired by Cassini — as well as other exploration spacecraft — into a single high-definition feature film, one that will allow viewers to experience the beauty, grandeur, and reality of the Solar System like never before.
“In Saturn’s Rings” (formerly “Outside In”) is slated for release in IMAX theaters, planetariums, and museums in the spring of 2014 — and the first official teaser trailer is below, released today. Check it out (or visit the YouTube page to watch in original, eye-melting 4k high-resolution):
“‘In Saturn’s Rings’ is a film that’s both personal and universal, experimental and sincere, science and spirit , non-narrative and documentary. The goal is to use large screen imagery, synchronized to powerful but moving music, to create an experience for those who see it, hear it and feel it.”
– “In Saturn’s Rings” official website
This is one film that I’ll be eagerly looking forward to over the next few months, without a doubt!
Read more on van Vuuren’s official film site here, and check out a full minute of film footage (originally released in 2011) on Vimeo here. Also, you can keep up with updates on the movie’s Twitter and Facebook pages.
Mosaic of Saturn seen in eclipse in September 2006. Earth is the bright dot just inside the F ring at upper left. (CICLOPS/NASA/JPL-Caltech/SSI)
Citizens of Earth, get ready for your Cassini close-up: once again the spacecraft is preparing to capture images of Saturn positioned between it and the Sun, allowing for incredible views of the ring system and its atmosphere — and also a tiny “pale blue dot” in the distance we call home.
Earth seen from Cassini (NASA/JPL/SSI)
The mosaic above was composed of images captured during such an eclipse event in September 2006, and quickly became an astronomical sensation. It’s not often we get an idea of what we look like from so far away, and seeing our entire world represented as a small speck of light nestled between Saturn’s rings is, to me anyway, both impressive and humbling.
Humbling because of how small we look, but impressive because as a species we have found a way to do it.
And next month, on Friday, July 19 between 21:27 and 21:42 UTC (5:27 – 5:42 p.m. EDT) Cassini will do it again.
“Ever since we caught sight of the Earth among the rings of Saturn in September 2006 in a mosaic that has become one of Cassini’s most beloved images, I have wanted to do it all over again, only better,” said Cassini imaging team leader, Carolyn Porco. “And this time, I wanted to turn the entire event into an opportunity for everyone around the globe, at the same time, to savor the uniqueness of our beautiful blue-ocean planet and the preciousness of the life on it.”
Porco was involved in co-initiating and executing the famous “Pale Blue Dot” image of Earth taken by NASA’s Voyager 1 from beyond the orbit of Neptune in 1990.
“It will be a day for all the world to celebrate,” she said.
The intent for the upcoming mosaic is to capture the whole scene, Earth and Saturn’s rings from one end to the other, in Cassini’s red, green and blue filters that can be composited to form a natural color view of what our eyes might see at Saturn. Earth and the Moon will also be imaged with a high resolution camera — something not yet done by Cassini.
We can all consider ourselves pretty lucky, too… this is the first time in history that we humans will know in advance that our picture is going to be taken from nearly a billion miles away.
“While Earth will be only about a pixel in size from Cassini’s vantage point 898 million miles [1.44 billion kilometers] away, the Cassini team is looking forward to giving the world a chance to see what their home looks like from Saturn,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory. “With this advance notice, we hope you’ll join us in waving at Saturn from Earth, so we can commemorate this special opportunity.”
So on July 19, remember to look up and wave… Cassini will be watching!
Read more on the CICLOPS news release here and on the NASA/JPL Cassini mission site here.
“That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives… There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”
Long-exposure Cassini NAC image of Saturn's D ring system (NASA/JPL-Caltech/SSI)
The closest to the planet itself, the hazy arcs of Saturn’s D ring may lack the reflective brilliance and sharply-defined edges of the other main rings, but they nevertheless possess their own ethereal beauty and mysteries. Here, the Cassini spacecraft has managed to capture the soft bands of the D ring in a long-exposure image acquired on April 2, 2013 — so long an exposure, in fact, that background stars seen through the rings appear as long vertical streaks, a testament to the ring’s dimness as well as the spacecraft’s continuing movement.
Beginning 8,768 km (5,448 miles) above the tops of Saturn’s clouds, the D ring is the innermost and thinnest segment of Saturn’s main ring system. Nearly transparent, the D ring extends about 7,500 km (4,660 miles) before transitioning to the considerably brighter C ring, which is over twice as wide.
The innermost portion of the C ring can be seen above along the left side. Saturn’s shadow blankets the lower right corner.
The cause of the alternating light-and-dark bands observed within the D ring isn’t yet known, but they may be the result of an impact by a comet or large meteor that set up recurring waves of material.
The view was acquired at a distance of approximately 510,000 kilometers (317,000 miles) from Saturn and at a phase angle of 147 degrees. Image scale is 2 miles (3 kilometers) per pixel.
This article comes from our archive, but we updated it with this video.
Saturn is my absolute favorite object in the night sky. When I was a child, I had a dog-eared book on the Solar System, which I read over and over, stopping and staring with wonder at the section on Saturn. How could a planet have rings of ice? What would it be like to fly out and visit the planet, to see the rings with your own eyes. How did it get all those strange moons?
When I was 14, I purchased my first telescope, a 4-inch Newtonian from a local company in Vancouver. It was summer, and one of the first planets, appearing just after sunset was Saturn. And my telescope had just enough power and magnification to resolve the planet and its famous rings. In fact, when I first looked at Saturn through the eyepiece, I couldn’t believe that I was now seeing the planet with my own eyes. It didn’t look quite like the photographs, but my imagination could fill in the gaps.
From those first observations, my fascination with astronomy and Saturn only grew, leading me to a career in science journalism. It’s funny to think how far I’ve come, and how I can trace everything back to those warm summer nights, looking at Saturn.
Think you know everything about Saturn? Think again. Here are 10 facts about Saturn, some you may know, and some you probably didn’t know.
1. Saturn is the least dense planet in the Solar System
Saturn has a density of 0.687 grams/cubic centimeter. Just for comparison, water is 1 g/cm3 and the Earth is 5.52. Since Saturn is less dense than water, it would actually float like an apple if you could find a pool large enough. Of course, why you’d want to ruin a pool with all that hydrogen, helium and ices…
2. Saturn is a flattened ball
Saturn spins so quickly on its axis that the planet flattens itself out into an oblate spheroid. Seriously, you see this by eye when you look at a picture of Saturn; it looks like someone squished the planet a little. Of course, it’s the rapid spinning that’s squishing it, causing the equator to bulge out.
While the distance from the center to the poles is 54,000 km, the distance from the center to the equator is 60,300 km. In other words, locations on the equator are approximately 6,300 km more distant from the center than the poles.
We have a similar phenomenon here on Earth, where points on the equator are more distant from the center of the Earth, but on Saturn, it’s much more extreme.
Cassini’s drawings of Saturn
3. The first astronomers thought the rings were moons.
When Galileo first turned his rudimentary telescope on Saturn in 1610, he could see Saturn and its rings, but he didn’t know what he was looking at. He though that the rings might actually be two large moons stuck to either side of Saturn – ears maybe?
It wasn’t until 1655 that the Dutch astronomer Christian Huygens used a better telescope to observe Saturn. He had the resolution to realize that the moons on either side of Saturn were actually rings: “a thin, flat ring, nowhere touching, and inclined to the ecliptic.” Huygens was also the first person to discover Saturn’s largest moon, Titan.
Voyager 2. Credit: NASA
4. Saturn has only been visited 4 times by spacecraft
Only 4 spacecraft sent from Earth have ever visited Saturn, and three of these were just brief flybys. The first was Pioneer 11, in 1979, which flew within 20,000 km of Saturn. Next came Voyager 1 in 1980, and then Voyager 2 in 1981. It wasn’t until Cassini’s arrival in 2004 that a spacecraft actually went into orbit around Saturn and captured photographs of the planet and its rings and moons.
Unfortunately, there are no future plans to send any more spacecraft to Saturn. A few missions have been proposed, including such radical concepts as a sailboat that could traverse the liquid methane lakes on Titan.
5. Saturn has 62 moons
Jupiter has 67 discovered moons, but Saturn is a close second with 62. Some of these are large, like Titan, the second largest moon in the Solar System. But most are tiny – just a few km across, and they have no official names. In fact, the last few were discovered by NASA’s Cassini orbiter just a few years ago. More will probably be discovered in the coming years.
6. The length of a day on Saturn was a mystery until recently
Determining the rotation speed of Saturn was actually very difficult to do, because the planet doesn’t have a solid surface. Unlike Mercury, you can’t just watch to see how long it takes for a specific crater to rotate back into view; astronomers needed to come up with a clever solution: the magnetic field.
To determine the rotational speed of Saturn, astronomers had to measure the rotation of the planet’s magnetic field. By one measurement, Saturn takes 10 hours and 14 minutes to turn on its orbit, but when Cassini approached Saturn, it clocked the rotation at 10 hours and 45 minutes. Astronomers now agree on an average day of 10 hours, 32 minutes and 35 seconds.
Saturn. NASA/JPL/Caltech
7. Saturn’s rings could be old, or they could be young.
It’s possible that Saturn’s rings have been around since the beginning of the Solar System – around 4.54 billion years ago. Or maybe they’re relatively brand new compared to the age of Saturn. Astronomers still don’t fully understand the origin of Saturn’s rings.
They might have formed recently, when a 300-km ice moon was torn apart by Saturn’s gravity, forming a ring around the planet.
It’s also possible that they’re the left over material when Saturn formed in the solar nebula. The material in the rings might have gotten jostled by Saturn’s gravity, and never could pull together into a cohesive Moon.
But astronomers have also found that the ring material looks just too clean to have formed so long ago, and could be as young as 100 million years old. It’s all just a big mystery.
Credit: NASA/JPL-Caltech/Space Science Institute
8. Sometimes the rings disappear
Well, they don’t actually disappear, but they look like they’re going away. Saturn’s axis is tilted, just like Earth. From our point of view, we see Saturn’s changing position as it takes its 30 year journey around the Sun. Sometimes, the rings are fully open, and we see them in all their glory, but other times we see the rings edge on – it looks like they’ve disappeared. This happened in 2008-2009, and will happen again in 2024-2025.
9. You can see Saturn with your own eyes
Saturn appears as one of the 5 planets visible with the unaided eye. If Saturn is in the sky at night, you can head outside and see it. To see the rings and the ball of the planet itself, you’ll want to peer through a telescope. But you can amaze your friends and family by pointing out that bright star in the sky, and let them know they’re looking at Saturn.
10. There could be life near Saturn
Not life on Saturn; the planet is way too hostile to support life. But there could be life on one of Saturn’s moons: Enceladus.
Water vapour geysers on Enceladus. Credit: NASA/JPL
NASA’s Cassini spacecraft recently discovered ice geysers blasting out of Enceladus’ southern pole. This means that some process is keep the moon warm enough that water can remain a liquid underneath the surface. And wherever we find liquid water on Earth, we find life.
