What’s This Ridge on Iapetus?

The strangest feature on Iapetus is the equatorial ridge. What could possibly create a feature like this?

To paraphrase the British geneticist J.B.S Haldane, “in my suspicion, the Universe is not only stranger than we suppose, it’s stranger than we can suppose.” The context was life and evolution, but he might as well been talking about Saturn’s moons. Those teeny worlds are some of the strangest places we’ve ever seen.

Titan is a massive moon with an atmosphere thicker than Earth’s. If it wasn’t for the bone crippling cold and unbreathable atmosphere, you could wear a pair of wings and fly around in the Titanic skies.

There’s Enceladus, an icy moon that blasts water out into space through geysers at its southern pole. But the Saturnian moon that fascinates me the most has got to be Iapetus, also known as Saturn’s yin-yang moon.

Here’s a photo captured by Cassini. Check out the bizarre surface features, where half of the moon is icy white and the other is brownish red. Astronomers believe this strange coloration comes from the ice on the warmer side sublimating away, leaving this darker material beneath.

Sure that’s a bit odd, but the strangest feature on Iapetus is the equatorial ridge. This feature measures 1,300 km long and it makes the moon look like a space walnut. Because of the heavy cratering on the ridge, astronomers know that it’s ancient, nearly as old as the moon itself. At 13 kms high, it’s tall enough to keep out the most persnickety white walker or wildling mammoth & giant battalion.

What could possibly create a feature like this?

Astronomers are of a few camps. The first think it formed through convective activity early on in the moon’s history. Saturn pulls Iapetus with its tremendous gravity, and the moon undergoes massive tidal forces. This generates heat in the moon’s interior, and it might have caused it to blob out at the equator.

A ridge that follows the equator of Saturn's moon Iapetus gives it the appearance of a giant walnut. This image was taken by the Cassini spacecraft. Credit: NASA/JPL/SSI
A ridge that follows the equator of Saturn’s moon Iapetus gives it the appearance of a giant walnut. This image was taken by the Cassini spacecraft. Credit: NASA/JPL/SSI

A second idea is that Iapetus consumed one of Saturn’s rings, billions of years ago. The moon might have slowly wandered through the ring plane, and accreted all the ring material, like snow piling up in front of a plow.

A third is that Iapetus was smashed into by a massive asteroid billions of years ago. This impact caused the moon to fly apart, but then mutual gravity pulled it back together. The force of this recombination squeezed out material at the equator, which then solidified in place.

Alternately, it might be a walnut from a Galactus family Christmas stocking. So which is it?

It turns out that Saturn has two more moons in its system with similar equatorial ridges. Its moon Atlas is just 15 km across, but it’s dominated by an equatorial ridge. It looks like a UFO, and Pan has a similar feature.

Saturn's relatively thin main rings are about 250,000 km (156,000 miles) in diameter. (Image: NASA/JPL-Caltech/SSI/J. Major)
Saturn’s relatively thin main rings are about 250,000 km (156,000 miles) in diameter. (Image: NASA/JPL-Caltech/SSI/J. Major)

Astronomers know that both of these created their ridges by pulling material out of the rings and piling it up on their surface. This is the mechanism that seems to match what’s going on with Iapetus.

One mystery, is how distantly Iapetus orbits Saturn. There’s no ring that far out, so where did it get the material to consume? Is it possible that Iapetus drifted outward, or had a ring system of its own?

You want puzzles? Iapetus is one of the strangest places in the Solar System, and it would be my candidate for a future orbiter or lander. Let’s explore it closer.

What’s your favorite bizarre object in the Solar System? Tell us in the comments below.

If Earth Had Saturn’s Rings, This is What it Would Look Like

We Earthlings love to dream, conjure and extrapolate. If you pose a question such as, “What if Earth had Saturn’s rings?” with all the resources available these days someone will not only answer the question but create some beautiful graphics to depict it! Yesterday, we saw this amazing graphic posted on reddit of a to-scale depiction of how Earth would look like with Saturn’s rings, and thanks to those who helped find the original source, the original image was created by John Brady at Astronomy Central. (We apologize… we originally credited the wrong person).

Of course, “What if Earth had Saturn’s rings?” is not a new question. In fact we’ve discussed it previously on Universe Today, and in 2013, illustrator and author Ron Miller put together some incredible visualizations of what Earth’s skies would look like with Saturn’s rings.

Also, last year someone on imgur put together a wonderful set of images of Earth with Saturn’s rings, as it would look from Earth’s Moon:

This video depicts rings around Earth, but the scale of the rings are not the size of Saturn’s:

Phil Plait discussed the problems that might arise for us if there were Earthrings, such as the rings would change the amount of sunlight reaching the Earth, and our view of the night sky would be hampered. And then Earth could potentially be shredded by ring debris.

Oh well, we can dream, can’t we?

See more great size comparisons of things in our Solar System and Universe at John Brady’s post on Astronomy Central, including a look at how many Earth’s would span across Saturn’s rings.

Saturn’s Ring Shows A Twist In Cassini’s Glimpse Of Planet

What’s up with this distortion? This picture from the Cassini spacecraft shows some kind of twist happening in the F ring of Saturn. Scientists in fact have seen other strange shapes in this delicate ring, indicating that something is disturbing it from time to time.

“Saturn’s F ring often appears to do things other rings don’t. In this Cassini spacecraft image, a strand of ring appears to separate from the core of the ring as if pulled apart by mysterious forces. Some ring scientists believe that this feature may be due to repeated collisions between the F ring and a single small object,” NASA stated this month.

There’s a debate in the scientific community about where the rings arose in the first place. “It’s been going back and forth for ages and it still goes back and forth. Are they old, or have they been there a long period of time? Are they new? I don’t know what to think, to be quite honest. I’m not being wishy-washy, I just don’t know what to think anymore,” Kevin Grazier, a planetary scientist with the Cassini mission for over 15 years, told Universe Today in December.

While this picture dates from October, you can check out Cassini images as they come in to NASA’s raw image database. Even in unprocessed form, the planet and its rings look beautiful — as you can clearly see in samples below.

The bulk of Saturn looms to the side of this shot of Saturn's rings taken in February 2014 by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute
The bulk of Saturn looms to the side of this shot of Saturn’s rings taken in February 2014 by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute
The variety of Saturn's rings is visible in this raw shot from the Cassini spacecraft taken in February 2014. Credit: NASA/JPL/Space Science Institute
The variety of Saturn’s rings is visible in this raw shot from the Cassini spacecraft taken in February 2014. Credit: NASA/JPL/Space Science Institute
Although Saturn's rings look solid and substantial in images such as this, they are made up of many tiny, icy objects collecting as thin as 6.2 miles (10 kilometers) deep.  Image taken by the Cassini spacecraft in February 2014. Credit: NASA/JPL/Space Science Institute
Although Saturn’s rings look solid and substantial in images such as this, they are made up of many tiny, icy objects collecting as thin as 6.2 miles (10 kilometers) deep. Image taken by the Cassini spacecraft in February 2014. Credit: NASA/JPL/Space Science Institute

Cassini Watches as Meteors Hit Saturn’s Rings

From tell-tale evidence, we know that Earth, our Moon and other bodies in our Solar System are constantly barraged with both small meteoroids and larger asteroids or comets. And sometimes – like in the case of seeing meteors fling across our sky, or flashes on the Moon or Jupiter getting hit by Comet Shoemaker-Levy 9 — we even get to watch as it happens. Now, for the first time the Cassini spacecraft has provided direct evidence of small meteoroids crashing into Saturn’s rings.

Researchers say that studying the impact rate of meteoroids from outside the Saturnian system helps scientists understand how different planet systems in our solar system formed.

Saturn’s rings act as very effective detectors of many kinds of surrounding phenomena, including the interior structure of the planet and the orbits of its moons. For example, a subtle but extensive corrugation that ripples 12,000 miles (19,000 kilometers) across the innermost rings tells of a very large meteoroid impact in 1983.

“These new results imply the current-day impact rates for small particles at Saturn are about the same as those at Earth — two very different neighborhoods in our solar system — and this is exciting to see,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It took Saturn’s rings acting like a giant meteoroid detector — 100 times the surface area of the Earth — and Cassini’s long-term tour of the Saturn system to address this question.”

The Saturnian equinox in summer 2009 was an especially good time to see the debris left by meteoroid impacts. The very shallow sun angle on the rings caused the clouds of debris to look bright against the darkened rings in pictures from Cassini’s imaging science subsystem.

This animation depicts the shearing of an initially circular cloud of debris as a result of the particles in the cloud having differing orbital speeds around Saturn. Image credit: NASA/Cornell

“We knew these little impacts were constantly occurring, but we didn’t know how big or how frequent they might be, and we didn’t necessarily expect them to take the form of spectacular shearing clouds,” said Matt Tiscareno, lead author of the paper and a Cassini participating scientist at Cornell University in Ithaca, N.Y. “The sunlight shining edge-on to the rings at the Saturnian equinox acted like an anti-cloaking device, so these usually invisible features became plain to see.”

Tiscareno and his colleagues now think meteoroids of this size probably break up on a first encounter with the rings, creating smaller, slower pieces that then enter into orbit around Saturn. The impact into the rings of these secondary meteoroid bits kicks up the clouds. The tiny particles forming these clouds have a range of orbital speeds around Saturn. The clouds they form soon are pulled into diagonal, extended bright streaks.

“Saturn’s rings are unusually bright and clean, leading some to suggest that the rings are actually much younger than Saturn,” said Jeff Cuzzi, a co-author of the paper and a Cassini interdisciplinary scientist specializing in planetary rings and dust at NASA’s Ames Research Center in Moffett Field, Calif. “To assess this dramatic claim, we must know more about the rate at which outside material is bombarding the rings. This latest analysis helps fill in that story with detection of impactors of a size that we weren’t previously able to detect directly.”

Source: JPL

Rain is Falling from Saturn’s Rings

Astronomers have known for years there was water in Saturn’s upper atmosphere, but they weren’t sure exactly where it was coming from. New observations have found water is raining down on Saturn, and it is coming from the planet’s rings.

“Saturn is the first planet to show significant interaction between its atmosphere and ring system,” said James O’Donoghue, a postgraduate researcher at the University of Leicester and author of a new paper published in the journal Nature. “The main effect of ring rain is that it acts to ‘quench’ the ionosphere of Saturn, severely reducing the electron densities in regions in which it falls.”

Using the Keck Observatory, O’Donoghue and a team of researchers found charged water particles falling from the planet’s rings into Saturn’s atmosphere. They also found the extent of the ring-rain is far greater, and falls across larger areas of the planet, than previously thought. The work reveals the rain influences the composition and temperature structure of parts of Saturn’s upper atmosphere.

O’Donoghue said the ring’s effect on electron densities is important because it explains why, for many decades, observations have shown electron densities to be unusually low at some latitudes at Saturn.

“It turns out a major driver of Saturn’s ionospheric environment and climate across vast reaches of the planet are ring particles located 120,000 miles [200,000 kilometers] overhead,” said Kevin Baines, a co-author on the paper, from the Jet Propulsion Laboratory. “The ring particles affect which species of particles are in this part of the atmospheric temperature.”

In the early 1980s, images from NASA’s Voyager spacecraft showed two to three dark bands on Saturn and scientists theorized that water could have been showering down into those bands from the rings. Then astronomers using ESA’s Infrared Observatory discovered the presence of trace amounts of water in Saturn’s atmosphere back in 1997, but couldn’t really find an explanation for why it was there and how it got there.

Then in 2011 observations with the Herschel space observatory determined water ice from geysers on Enceladus formed a giant ring of water vapor around Saturn.

But the bands seen by Voyager were not seen again until 2011 as well, when the team observed the planet with Keck Observatory’s NIRSPEC, a near-infrared spectrograph that combines broad wavelength coverage with high spectral resolution, allowing the observers to clearly see subtle emissions from the bright parts of Saturn.

The ring rain’s effect occurs in Saturn’s ionosphere (Earth has a similar ionosphere), where charged particles are produced when the otherwise neutral atmosphere is exposed to a flow of energetic particles or solar radiation. When the scientists tracked the pattern of emissions of a particular hydrogen molecule consisting of three hydrogen atoms (rather than the usual two), they expected to see a uniform planet-wide infrared glow.

What they observed instead was a series of light and dark bands with a pattern mimicking the planet’s rings. Saturn’s magnetic field “maps” the water-rich rings and the water-free gaps between rings onto the planet’s atmosphere.

They surmised that charged water particles from the planet’s rings were being drawn towards the planet by Saturn’s magnetic field and neutralizing the glowing triatomic hydrogen ions. This leaves large “shadows” in what would otherwise be a planet-wide infrared glow. These shadows cover 30 to 43 percent of the planet’s upper atmosphere surface from around 25 to 55 degrees latitude. This is a significantly larger area than suggested by the Voyager images.

Both Earth and Jupiter have a very uniformly glowing equatorial region. Scientists expected this pattern at Saturn, too, but they instead saw dramatic differences at different latitudes.

“Where Jupiter is glowing evenly across its equatorial regions, Saturn has dark bands where the water is falling in, darkening the ionosphere,” said Tom Stallard, one of the paper’s co-authors at Leicester. “We’re now also trying to investigate these features with an instrument on NASA’s Cassini spacecraft. If we’re successful, Cassini may allow us to view in more detail the way that water is removing ionized particles, such as any changes in the altitude or effects that come with the time of day.”

Sources: Keck Observatory
, Nature.

Outer Space – Mind Blowing Video from Jupiter and Saturn

Video Caption: This mesmerizing video unveils incredibly amazing sequences around Jupiter and Saturn from NASA’s Cassini and Voyager missions set to stirring music by “The Cinematic Orchestra -That Home (Instrumental)”. Credit: Sander van den Berg

Don’t hesitate 1 moment ! Look and listen to this mind blowing video of the Jupiter and Saturnian systems.

If you love the wonders of the hitherto unknown Universe unveiled before your eyes – and long to explore – feast your eyes on this short new video right now titled simply; “Outer Space”. Continue reading “Outer Space – Mind Blowing Video from Jupiter and Saturn”

Cassini’s Majestic Saturn Moon Quintet


Check out this gorgeous new portrait of a Saturnian moon quintet taken by Earths’ emissary – NASA’s Cassini Orbiter. The moons are majestically poised along a backdrop of Saturn’s rings, fit for an artist’s canvas.

Janus, Pandora, Enceladus, Mimas and Rhea are nearly lined up (from left to right) in this view acquired by Cassini at a distance of approximately 684,000 miles (1.1 million kilometers) from Rhea and 1.1 million miles (1.8 million kilometers) from Enceladus.

The newly released image was taken by Cassini’s narrow angle camera on July 29, 2011. Image scale is about 4 miles (7 kilometers) per pixel on Rhea and 7 miles (11 kilometers) per pixel on Enceladus.

Cassini will stage a close flyby of Enceledus – Satarn’s geyser spewing moon – in about two weeks, swooping within 99 km

Moon Facts from JPL:
Janus (179 kilometers, or 111 miles across) is on the far left. Pandora (81 kilometers, or 50 miles across) orbits between the A ring and the thin F ring near the middle of the image. Brightly reflective Enceladus (504 kilometers, or 313 miles across) appears above the center of the image. Saturn’s second largest moon, Rhea (1,528 kilometers, or 949 miles across), is bisected by the right edge of the image. The smaller moon Mimas (396 kilometers, or 246 miles across) can be seen beyond Rhea also on the right side of the image.

This view looks toward the northern, sunlit side of the rings from just above the ring plane. Rhea is closest to Cassini here. The rings are beyond Rhea and Mimas. Enceladus is beyond the rings.

The simple graphic below shows dozens of Saturn’s moons – not to scale. So far 62 have been discovered and 53 have been officially named.

Saturn’s moons. Click on link below to learn more about each moon. Credit: NASA/JPL

Learn more about Saturn’s moons at this link

List of Saturn’s officially named moons:
Aegaeon, Aegir, Albiorix, Anthe, Atlas, Bebhionn, Bergelmir, Bestla, Calypso, Daphnis, Dione, Enceladus, Epimetheus, Erriapus, Farbauti, Fenrir, Fornjot, Greip, Hati, Helene, Hyperion, Hyrrokkin, Iapetus, Ijiraq, Janus, Jarnsaxa, Kari, Kiviuq, Loge, Methone, Mimas, Mundilfari, Narvi, Paaliaq, Pallene, Pan, Pandora, Phoebe, Polydeuces, Prometheus, Rhea, Siarnaq, Skadi, Skoll, Surtur, Suttung, Tarqeq, Tarvos, Telesto, Tethys, Thrym, Titan and Ymir.

Why Does Saturn Have Rings

Why Does Saturn Have Rings

Saturn has fascinated amateurs and professionals alike for centuries. As quickly as the planet’s ring system was discovered the popular question became ‘why does Saturn have rings?’ usually followed by ‘what are Saturn’s rings made of?’. Well, here are the answers to both questions.

The simplest answer as to why Saturn has rings and what they are made of is that the planet has accumulated a great deal of dust, particles, and ice at varying distances from its surface. These items are most likely trapped by gravity. The rings appear because of the wavelengths of light reflected by these rings of debris.

Some scientists speculate that Saturn may be too big. Its gravitational pull is so strong that it has been able to snatch debris from space. Some of which is as large as an entire building. That pull is why it has at least 62 moons. Those moons contribute dust to the rings as well as absorb dust from the rings.

A common theory as to how all of the material initially accumulated in Saturn’s rings is a series of asteroid impacts. Not with the planet, but with the moons around it. After the impact the remnants of the asteroids and the debris from the moons could not escape the gravitational pull of the planet.

One other theory holds that the rings of Saturn formed as other moons broke apart in ancient times. Additionally, this theory states that some of the material could be from earlier, during the formation of the solar system, and Saturn could not accrete the material while it was forming and it has been in orbit ever since.

No matter which theory you believe, the rings of Saturn are spectacular. After researching Saturn’s rings a little more, be sure to investigate the ring systems around Neptune, Uranus, and Jupiter. Each system is fainter than Saturn’s, but still interesting.

We have written many articles about Saturn for Universe Today. Here’s an article about the color of Saturn, and here are some pictures of Saturn.

If you’d like more info on Saturn, check out Hubblesite’s News Releases about Saturn. And here’s a link to the homepage of NASA’s Cassini spacecraft, which is orbiting Saturn.

We’ve also recorded an episode of Astronomy Cast all about Saturn. Listen here, Episode 59: Saturn.


Saturn’s Rings Formed from Large Moon’s Destruction


The formation of Saturn’s rings has been one of the classical if not eternal questions in astronomy. But one researcher has provided a provocative new theory to answer that question. Robin Canup from the Southwest Research Institute has uncovered evidence that the rings came from a large, Titan-sized moon that was destroyed as it spiraled into a young Saturn.

Over the years, different theories have evolved on how the rings formed around Saturn. The two leading theories involve a small moon that was shattered by meteor impacts, or the tidal disruption of a comet coming too close to Saturn.

But Saturn’s main rings are about 90% water ice by mass, and because bombardment of the rings by micrometeoroids increases their rock content over time, Canup said the rings’ current composition implies that they were essentially pure ice when they formed.

However, disruption of a small moon would generally lead to a mixed rock-ice ring, while tidal disruptions of comets would occur much more often at Jupiter, Uranus and Neptune than at Saturn.

New insights into the nature of Saturn’s rings are revealed in this panoramic mosaic of 15 images taken during the planet’s August 2009 equinox. Image credit: NASA/JPL/SSI

Additionally, neither of these theories would explain Saturn’s inner moons, which have low enough densities that they too must be comprised of nearly pure ice.

Canup’s new alternative theory is that Titan-sized moon with a rocky core and an icy mantle spiraled into Saturn early in solar system history. Tidal forces ripped off part of the icy mantle, distributing it into what would become the rings. But the rocky core was made of more durable material that held together until it hit Saturn’s surface. “The end result is a pure ice ring,” Canup said in an article in Nature.

Over time the ring spreads out and its mass decreases, and icy moons are created. Due to changes in the evolving Saturn system, these “spawned” moons then spiraled outward rather than inward. In this way, ice rings and ice-enhanced inner moons originate as a primordial byproduct of the same process that produces Saturn’s regular satellite system, making the whole process simpler than if there were several events.

Canup studies formation events with detailed computer simulations, including studying how our own Moon formed.

She presented her findings at the American Astronomical Society’s Division for Planetary Science meeting this week, in Pasadena, California, and her presentation was detailed in an article in Nature.

Sources: Canup’s abstract, Nature

Prometheus: the Michelangelo of Saturn


I’ve frequently said the Cassini spacecraft is an artist, so when Carolyn Porco, the mission’s imaging team lead, mentioned on Twitter that Saturn’s moon Prometheus is akin to Michelangelo, I had to take a look. Wow, this gorgeous image is suitable for framing! Visible in the perturbed, thin F ring, is the potato-shaped Prometheus, and having performed the perturbing, it continues in its orbit. Click the image for the super-huge version.

Prometheus (148 kilometers, 92 miles across) periodically creates streamer-channels in the F ring, and the moon’s handiwork can be seen as the dark channels. Here’s a movie made from Cassini images showing this process:

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 1, 2010. A star is also visible through the rings near the center right of the image.

There are also some additional features in the F ring, courtesy of Prometheus.

This Cassini image shows icy particles in Saturn’s F ring clumping into giant snowballs as the moon Prometheus makes multiple swings by the ring. Scientists say that the gravitational pull of the moon sloshes ring material around, creating wake channels that trigger the formation of objects as large as 20 kilometers (12 miles) in diameter.

“Scientists have never seen objects actually form before,” said Carl Murray, a Cassini imaging team member based at Queen Mary, University of London. “We now have direct evidence of that process and the rowdy dance between the moons and bits of space debris.”

Read more about these fans and snowballs in this JPL article.