Cassini Archives

November 1, 2016November 2, 2016 by Matt Williams

Even Though it’s an Alien World, Titan’s Canyons Would Look Very Familiar

In this near-infrared mosaic, the sun shines off of the seas on Saturn's moon, Titan. Credit: NASA/JPL-Caltech/University of Arizona/University of Idaho

Titan is tough moon to study, thanks to its incredibly thick and hazy atmosphere. But when astronomers have ben able to sneak a peak beneath its methane clouds, they have spotted some very intriguing features. And some of these, interestingly enough, are reminiscent of geographical features here on Earth. For instance, Titan is the only other body in the Solar System that is known to have a cycle where liquid is exchanged between the surface and the atmosphere.

For example, previous images provided by NASA’s Cassini mission showed indications of steep-sided canyons in the northern polar region that appeared to be filled with liquid hydrocarbons, similar to river valleys here on Earth. And thanks to new data obtained through radar altimetry, these canyons have been shown to be hundreds of meters deep, and have confirmed rivers of liquid methane flowing through them.

This evidence was presented in a new study titled “Liquid-filled canyons on Titan” – which was published in August of 2016 in the journal Geophysical Research Letters. Using data obtained by the Cassini radar altimeter in May 2013, they observed channels in the feature known as Vid Flumina, a drainage network connected to Titan’s second largest hydrocarbon sea in the north, Ligeia Mare.

Saturn's largest moon, Titan, has features that resemble Earth's geology, with deep, steep-sided canyons. Credit: NASA/JPL/Cassini — *Saturn’s largest moon, Titan, has features that resemble Earth’s geology, with deep, steep-sided canyons. Credit: NASA/JPL/Cassini*

Analysis of this information showed that the channels in this region are steep-sided and measure about 800 m (half a mile) wide and between 244 and 579 meters deep (800 – 1900 feet). The radar echoes also showed strong surface reflections that indicated that these channels are currently filled with liquid. The elevation of this liquid was also consistent with that of Ligeia Mare (within a maring of 0.7 m), which averages about 50 m (164 ft) deep.

This is consistent with the belief that these river channels in area drain into the Ligeia Mare, which is especially interesting since it parallels how deep-canyon river systems empty into lakes here on Earth. And it is yet another example of how the methane-based hydrological cycle on Titan drives the formation and evolution of the moon’s features, and in ways that are strikingly similar to the water cycle here on Earth.

Alex Hayes – an assistant professor of astronomy at Cornell, the Director of the Spacecraft Planetary Imaging Facility (SPIF) and one of the authors on the paper – has conducted seversal studies of Titan’s surface and atmosphere based on radar data provided by Cassini. As he was quoted as saying in a recent article by the Cornell Chronicler:

“Earth is warm and rocky, with rivers of water, while Titan is cold and icy, with rivers of methane. And yet it’s remarkable that we find such similar features on both worlds. The canyons found in Titan’s north are even more surprising, as we have no idea how they formed. Their narrow width and depth imply rapid erosion, as sea levels rise and fall in the nearby sea. This brings up a host of questions, such as where did all the eroded material go?”

The northern polar area of Titan and Vid Flumina drainage basin. (left) On top of the image, the Ligeia Mare; in the lower right the North Kraken Mare; the two seas are connected each other by a labyrinth of channels. On the left, near the North pole, the Punga Mare. Red arrows indicate the position of the two flumina significant for this work. At the end of its mission (15 September 2017) the Cassini RADAR in its imaging mode (SAR+ HiSAR) will have covered a total area of 67% of the surface of Titan [Hayes, 2016]. Map credits: R. L. Kirk. (right) Highlighted in yellow are the half-power altimetric footprints within the Vid Flumina drainage basin and the Xanthus Flumen course for which specular reflections occurred. At 1400?km of spacecraft altitude, the Cassini antenna 0.35° central beam produces footprints of about 8.5?km in diameter (diameter of yellow circles). Credit: NASA/JPL — *Cassini image of the northern polar area of Titan and Vid Flumina drainage basin, showing Ligeia Mare (left) and the Vid Flumina drainage basin (right). Credit: R.L. Kirk/NASA/JPL*

A good question indeed, since it raises some interesting possibilities. Essentially, the features observed by Cassini are just part of Titan’s northern polar region, which is covered by large standing bodies of liquid methane – the largest of these being Kraken Mare, Ligeia Mare and Punga Mare. In this respect, the region is similar to glacially eroded fjords on Earth.

However, conditions on Titan do not allow for the presence of glaciers, which rules out the likelihood that retreating sheets of ice could have carved these canyons. So this naturally begs the question, what geological forces created this region? The team concluded that there were only two likely possibilities – which included changes in the elevation of the rivers, or tectonic activity in the area.

Ultimately, they favored a model where the variation in surface elevation of liquid drove the formation of the canyons – though they acknowledge that both tectonic forces and sea level variations played a role. As Valerio Poggiali, an associate member of the Cassini RADAR Science Team at the Sapienza University of Rome and the lead author of the paper, told Universe Today via email:

“What the canyons on Titan really mean is that in the past sea level was lower and so erosion and canyon formation could take place. Subsequently sea level has risen and backfilled the canyons. This presumably takes place over multiple cycles, eroding when sea level is lower, depositing some when it is higher until we get the canyons we see today. So, what it means is that sea level has likely changed in the geological past and the canyons are recording that change for us.”

Titan's Ligeia Mare. Credit: NASA/JPL/USGS — *Titan’s second largest methane lake, Ligeia Mare. Credit: NASA/JPL/USGS*

In this respect, there are many more Earth examples to choose from, all of which are mentioned in the study:

“Examples include Lake Powell, a reservoir on the Colorado River that was created by the Glen Canyon Dam; the Georges River in New South Wales, Australia; and the Nile River gorge, which formed as the Mediterranean Sea dried up during the late Miocene. Rising liquid levels in the geologically recent past led to the flooding of these valleys, with morphologies similar to those observed at Vid Flumina.”

Understanding the processes that led to these formations is crucial to understanding the current state of Titan’s geomorphology. And this study is significant in that it is the first to conclude that the rivers in the Vid Flumina region were deep canyons. In the future, the research team hopes to examine other channels on Titan that were observed by Cassini to test their theories.

Once again, our exploration of the Solar System has shown us just how weird and wonderful it truly is. In addition to all its celestial bodies having their own particular quirks, they still have a lot in common with Earth. By the time the Cassini mission is complete (Sept. 15th, 2017), it will have surveyed 67% the surface of Titan with its RADAR imaging instrument. Who knows what other “Earth-like” features it will notice before then?

Further Reading: Geophysical Research Letters

October 28, 2016 by Matt Williams

If it Wasn’t Already Strange Enough, now Saturn’s Hexagon Storm is Changing Color

Saturn makes a beautifully striped ornament in this natural-color image, showing its north polar hexagon and central vortex (Credit: NASA/JPL-Caltech/Space Science Institute)

Ever since the Voyager 2 made its historic flyby of Saturn, astronomers have been aware of the persistent hexagonal storm around the gas giant’s north pole. This a six-sided jetstream has been a constant source of fascination, due to its sheer size and immense power. Measuring some 13,800 km (8,600 mi) across, this weather system is greater in size than planet Earth.

And thanks to the latest data to be provided by the Cassini space probe, which entered orbit around Saturn in 2009, it seems that this storm is even stranger than previously thought. Based on images snapped between 2012 and 2016, the storm appears to have undergone a change in color, from a bluish haze to a golden-brown hue.

The reasons for this change remain something of a mystery, but scientists theorize that it may be the result of seasonal changes due to the approaching summer solstice (which will take place in May of 2017). Specifically, they believe that the change is being driven by an increase in the production of photochemical hazes in the atmosphere, which is due to increased exposure to sunlight.

Natural color images taken by NASA's Cassini wide-angle camera, showing the changing appearance of Saturn's north polar region between 2012 and 2016.. Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University — Natural color images taken by NASA’s Cassini wide-angle camera, showing the changing appearance of Saturn’s north polar region between 2012 and 2016.. Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University

This reasoning is based in part on past observations of seasonal change on Saturn. Like Earth, Saturn experiences seasons because its axis is tilted relative to its orbital plane (26.73°). But since its orbital period is almost 30 years, these seasons last for seven years.

Between November 1995 and August 2009, the hexagonal storm also underwent some serious changes, which coincided with Saturn going from its Autumnal to its Spring Equinox. During this period, the north polar atmosphere became clear of aerosols produced by photochemical reactions, which was also attributed to the fact that the northern polar region was receiving less in the way of sunlight.

However, since that time, the polar atmosphere has been exposed to continuous sunlight, and this has coincided with aerosols being produced inside the hexagon, making the polar atmosphere appear hazy. As Linda J. Spilker, the Cassini mission’s project scientist, told Universe Today via email:

“We have seen dramatic changes in the color inside Saturn’s north polar hexagon in the last 4 years. That color change is probably the result of changing seasons at Saturn, as Saturn moves toward northern summer solstice in May 2017. As more sunlight shines on the hexagon, more haze particles are produced and this haze gives the hexagon a more golden color.”

This diagram shows the main events of Saturn's year, and where in the Saturnian year the Voyager 1 and Cassini missions occurred. Credit: Ralph Lorenz — *Diagram showing he main events of Saturn’s year, and where in the Saturnian year the Voyager 1 and Cassini missions occurred. Credit: Ralph Lorenz*

All of this has helped scientists to test theoretical models of Saturn’s atmosphere. In the past, it has been speculated that this six-sided storm acts as a barrier that prevents outside haze particles from entering. The previous differences in color – the planet’s atmosphere being golden while the polar storm was darker and bluish – certainly seemed to bear this out.

The fact that it is now changing color and starting to look more like the rest of the atmosphere could mean that the chemical composition of the polar region is now changing and becoming more like the rest of the planet. Other effects, which include changes in atmospheric circulation (which are in turn the result of seasonally shifting solar heating patterns) might also be influencing the winds in the polar regions.

Needless to say, the giant planets of the Solar System have always been a source of fascination for scientists and astronomers. And if these latest images are any indication, it is that we still have much to learn about the dynamics of their atmospheres.

“It is very exciting to see this transformation in Saturn’s hexagon color with changing seasons,” said Spilker. “With Saturn seasons over 7 years long, these new results show us that it is certainly worth the wait.”

R. G. French (Wellesley College) et al., NASA, ESA, and The Hubble Heritage Team (STScI/AURA) — *The seasons on Saturn, visualized with images taken by the Hubble Heritage Team. Credit: R. G. French (Wellesley College) et al./NASA/ESA/Hubble Heritage Team (STScI/AURA)*

It also shows that Cassini, which has been in operation since 1997, is still able to provide new insights into Saturn and its system of moons. In recent weeks, this included information about seasonal variations on Titan, Saturn’s largest moon. By April 22nd, 2017, the probe will commence its final 22 orbits of Saturn. Barring any mission extensions, it is scheduled enter into Saturn’s atmosphere (thus ending its mission) on Sept. 15th, 2017.

Further Reading: NASA/JPL/Caltech

May 11, 2016May 15, 2016 by Evan Gough

New Composite Image Of Saturn’s Polar Vortex Mesmerizes

This image of Saturn's southern polar vortex reveals previously unseen detail of the giant storm. Image: NASA/JPL/Space Science Institute

Atmospheric features on our Solar System’s gas giants dwarf anything similar on Earth. Earth’s atmosphere spawns hurricanes as larger as 1500 km in diameter. But on Saturn, a feature called the southern polar vortex has an eye that is 8,000 km across, or two thirds the diameter of the entire Earth.

A new high-resolution of Saturn’s southern polar vortex captured by the Cassini probe is ten times more detailed than any previous picture, and reveals details that were previously unseen. The image, which is a composite of two images taken by Cassini in July 2008, was captured when the spacecraft was 392,000 km from Saturn, and 56º below the plane of Saturn’s rings. Despite the distance and position, the image still has a resolution of 2 km per pixel.

Previous images of the vortex revealed clouds of immense proportions ringing the edge of the vortex, but showed the vortex itself to be clear. This is similar to a hurricane on Earth, where the eye itself is clear, but is ringed by wall-clouds of towering heights. This new image shows cloud formations within the vortex itself. The vortex is punctuated with wispy white cloud formations, and a smaller vortex at 10:00 within the larger formation.

The clouds inside the vortex are more than just pretty curiosities, of course. They are deep convective structures welling up from deep within Saturn’s atmosphere, and they form their own distinctive ring. This is all the more interesting because the eye of the vortex itself is generally clear, and is considered by scientists to be an area of downwelling.

The convection on display in Saturn’s southern polar vortex is an important clue to understanding how Saturn transfers energy through its atmosphere. On Earth, hurricanes are caused by warm water, and they move across the surface of the ocean as the warm water does.

Saturn, of course, has no liquid ocean, and the vortex is powered by warm atmospheric gases from deeper in Saturn. As they rise and cool they condense into clouds. The vortex also remains stationary, rather than following a warm mass of water. It’s locked into position over Saturn’s south pole.

Cassini’s narrow angle camera captured this new image, using a combination of two spectral filters. One was sensitive to wavelengths of polarized visible light centered at 617 nanometers, and the other to infrared light centered at 750 nanometers.

These two previously released infrared images of Saturn show the entire south polar region with the hurricane-like vortex in the center. The top image shows the polar region in false color, with red, green, and blue depicting the appearance of the pole in three different near-infrared colors (NASA/JPL/University of Arizona)

Cassini is a joint mission of NASA, the ESA, and the Italian Space Agency. It was launched in 1997, and has had its mission extended to September 2017. Cassini will end its mission in what the team operating Cassini is calling a Grand Finale. This will be a series of deep dives between Saturn and its rings, and will end with the spacecraft plunging into Saturn’s atmosphere.

To see a gallery of Cassini images, go here.

At Universe Today, we’ve written about Saturn’s polar vortices before. Have a look:

Violent Polar Cyclones on Saturn Imaged in Unprecedented Detail by Cassini

Hexagonal Structure at Saturn’s North Pole

March 11, 2016March 18, 2016 by Evan Gough

Cassini Watches Star Through Enceladus’ Plume

When the Cassini probe first saw the plumes coming from Saturn’s moon Enceladus, it was a surprise. When it dipped through the plumes, some questions about the basic nature of the phenomenon were answered. But there are still many more questions, and today Cassini has an opportunity to find some answers.

Cassini will be in a perfect position today to observe the light from Epsilon Orionis, the central star in Orion’s belt, as it passes through Enceladus’ plume. This type of observation is known as a stellar occultation, and it promises to provide new information about the composition and density of the plume. Cassini’s Ultraviolet Imaging Spectrograph (UVIS) will do the capturing, and once the information is relayed back to Earth, it will be analyzed for clues.

An artist's impression of the plumes coming from Enceladus. Image: NASA/JPL. — An artist’s impression of the plumes coming from Enceladus. Image: NASA/JPL.

We already know a few things about Enceladus’ plumes. First of all, Enceladus itself is any icy world, with subsurface oceans. The moon is locked in an orbital resonance, which creates its eccentric orbit. This eccentric orbit is responsible for heating the south polar oceans, which drives material through the ice sheets and creates its stunning plumes, in a process known as cryovolcanism. (Radioactive decay might also have something to do with heating.)

Cassini has been at Saturn’s system for 12 years, and has gradually painted a more detailed picture of Enceladus. Over time, we’ve learned that the plumes themselves are similar to what comets are made of. Cassini initially detected mostly water vapor, with traces of molecular nitrogen, methane, and carbon dioxide. Later, the presence of the hydrocarbons propane, formaldehyde, and acetylene was confirmed.

This is all very interesting, but why would anyone other than chemistry geeks care? Because the universe, including our Solar System, is largely a cold, sterile place. And the plumes coming from Enceladus indicate the presence of water, potentially warm, salty, water at that. And warm water might mean life, or the potential for life.

Cassini has previously observed two other stellar occultations. But with today’s observation, we stand to learn even more about the plumes of Enceladus. We’ll not only learn more about their density and composition, but since is the third such occultation to be observed, we’ll learn something about the plume’s behaviour over time. We probably won’t learn anything definitive about Enceladus’ life-supporting potential, but we will almost certainly find another piece of the puzzle, and fill in a blank spot in our knowledge.

And that’s what science is all about.

March 3, 2016March 18, 2016 by Evan Gough

Surfing On Titan Would Be Best In Summer

The view from the beach on Titan? Image: NASA — The view from the beach on Titan? A recent study has shown that Titan's seas experience very low waves, making it a perfect place for a probe to set down.Credit: NASA

Space is mostly vast and empty. So whenever we notice something like ripples on a lake, on the frozen moon of a gas giant, we take notice.

At a meeting of the American Geophysical Union in San Francisco this week, it was reported that Cassini images of Saturn’s moon Titan showed light being reflected from the Ligeia Mare, a frigid sea of hydrocarbons on that moon. Subsequent images showed the same phenomenon on two other seas of Titan, as well. These are thought to be waves, the first waves detected anywhere other than Earth, and suggest that Titan has more geophysical activity than previously thought.

Surfers on Earth, known for seeking out remote and secretive locations, shouldn’t get too excited. According to mathematical modelling and radar imagery, these waves are only 1.5 cm (0.6 inches) tall, and they’re moving only 0.7 metres (2.3 feet) per second. Plus, they’re on a sea of liquid hydrocarbons—mostly methane—that is a frigid -180 degrees Celsius (-292 F.)

The left image shows a mosaic of images of Titan taken by the Cassini spacecraft in near infrared light. Titan’s polar seas are visible as sunlight glints off of them. The right image is a radar image of Kraken Mare. Credit: NASA Jet Propulsion Laboratory.

Planetary scientists are taking note, though, because these waves show that Titan has an active environment, rather than just being a moon frozen in time. It’s thought that the change in seasons on Titan is responsible for these waves, as Titan begins its 7 year summer. Processes related to the changing seasons on Titan have created winds, which have cause these ripples.

There’s other evidence of active weather on Titan, including dunes, river channels, and shorelines. But this is the first observation of active weather phenomena, rather than just the results. All together, it shows that Titan is a more active, dynamic environment than previously thought.

Titan’s hydrocarbon lakes are thought to be up to 200 metres (656 ft.) deep, and are clustered around the north polar region. Just one of its lakes is thought to contain approximately 9,000 cubic km of methane, which is about 40 times more than the Earth’s reserves of oil and gas.

Titan is the second largest moon in the Solar System, second only to Ganymede, and both moons are larger than the planet Mercury. Titan was discovered in 1655 by Christiaan Huygens.

February 25, 2016March 18, 2016 by Bob King

Search Narrows For Planet Nine

Based on a careful study of Saturn's orbit and using mathematical models, French scientists were able to whittle down the search region for Planet Nine to "possible" and "probable" zones. Source: CNRS, Cote d'Azur and Paris observatories. Credit:

The imagined view from Planet Nine looking back toward the sun. Astronomers think the huge, distant planet is gaseous, similar to the other giant planets in our solar system. — An imagined view from Planet Nine looking back toward the Sun. Astronomers think the massive, distant planet is gaseous, similar to the other giant planets in our Solar System. Credit: Wikipedia

Last month, planetary scientists Mike Brown and Konstantin Batygin of the California Institute of Technology found evidence of a giant planet tracing a bizarre, highly elongated orbit in the outer Solar System. Nicknamed Planet Nine, it’s estimated to be 10 times more massive than Earth with a diameter as large as 16,000 miles (25,750 km). The putative planet orbits about 20 times farther from the Sun on average than Neptune or some 56 billion miles away; at that tremendous distance it would take between 10,000 and 20,000 years to complete one orbit around the Sun.

The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the solar system. Batygin and Brown show that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech/R. Hurt (IPAC); [Diagram created using WorldWide Telescope.] — The six most distant known objects in the Solar System with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Also, when viewed in three dimensions, they tilt nearly identically away from the plane of the solar system. Batygin and Brown showed that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech/R. Hurt (IPAC); Diagram created using WorldWide Telescope

Planet Nine’s existence is inferred through mathematical modeling and computer simulations based on the clustering of six remote asteroids in the Kuiper Belt, a vast repository of icy asteroids and comets beyond Neptune. Brown and Batyginsay there’s only a 0.007% chance or about 1 in 15,000 that the clustering could be a coincidence.

All well and good. But with such an enormous orbit, astronomers face the daunting task of searching vast swaths of space for this needle in a haystack. Where to begin? A study done by a team of French scientists may help narrow the search. In a recent paper appearing in Astronomy and Astrophysics, astronomer Agnes Fienga and colleagues looked at what effect a large Kuiper Belt planet would have on the orbits of other planets in the Solar System, focusing their study on Saturn. Thanks to NASA’s Cassini orbiter, which has been orbiting Saturn since 2004, we can precisely calculate Saturn’s position along its orbit.

Based on the planet’s “residuals”, the difference between the calculated position of Saturn versus what was actually observed, the team was able to exclude two sections of its potential orbit and home in on “probable” swath and a much larger “possible” section of the orbit. The process may sound familiar, since it was the one used to discover another planet more than 150 years ago — Neptune. Back then, irregularities (residuals) in the motion of Uranus led astronomers in 1847 to predict a more distant 8th planet as the cause. On September 24, 1846, Johann Galle discovered Neptune only 1° from its position predicted by French mathematician Urbain LeVerrier.

While the current solution for Planet Nine doesn’t come anywhere near as close, it’s a step in the right direction.

February 3, 2016February 3, 2016 by Jason Major

Saturn’s Rings Continue to Surprise Scientists

Composite image of a backlit Saturn, made from Cassini images acquired on July 19, 2013. Saturn's B ring appears darkest and densest here. (NASA/JPL-Caltech/Space Science Institute)

If you try to apply simple common sense to how Saturn’s rings really work you’re going to be sorely mistaken: the giant planet’s signature features run circles around average Earthly intuition. This has been the case for centuries and is still true today after recent news from Cassini that the most opaque sections of rings aren’t necessarily the densest; with Saturn looks literally are deceiving.

Continue reading “Saturn’s Rings Continue to Surprise Scientists”

November 30, 2015December 23, 2015 by Nancy Atkinson

Enceladus, the Jet-Powered Water World

The crescent of Saturn's moon Enceladus hangs above the planet's rings in this image from the Cassini spacecraft. Water jets that spew from the moon’s south pole region are also visible. Credit: NASA/JPL-Caltech/Space Science Institute

I don’t think I’ll ever tire of seeing pictures of Saturn’s moon Enceladus, with those captivating water jets and plumes at its South Pole. And this new images from the Cassini mission is just stunning – and intriguing. Carolyn Porco, the Cassini imaging team lead described the image on Twitter: “Be moved by crescent Enceladus with its ghostly geysers floating above Saturn’s glowing rings.”

There are over 100 geyser jets of varying sizes near Enceladus’s south pole spraying water vapor, icy particles, and organic compounds out into space. Enticingly, this distant and small moon (313 miles or 504 kilometers across) has a global subsurface ocean of liquid water, as tidal forces from Enceladus’ orbital relationship to Saturn and another moon, Dione heats the interior.

Liquid water and the observation of organic chemicals in the plumes of Enceladus make this moon of high astrobiological interest to scientists. In a 2014 paper by Porco and astrobiologist Chris McKay, the due wrote that Enceladus’ “steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. … No other world has such well-studied indications of habitable conditions.”

While the rings of Saturn are also beautiful, they are they are frozen and geologically dead. “The small ring particles are too tiny to retain internal heat and have no way to get warm,” the Cassini imaging team explained on the CICLOPS website.

This image was taken in July of 2015, and was not part of two close flybys of Enceladus in October of this year. Project scientist Linda Spilker hinted there might be some new discoveries from those flybys (see images here and here), as she said, “Cassini’s stunning images are providing us a quick look at Enceladus from this ultra-close flyby, but some of the most exciting science is yet to come.”

This beautiful view of Enceladus and Saturn’s rings looks toward the unilluminated side of the rings from about 0.3 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 29, 2015.

The view was acquired at a distance of approximately 630,000 miles (1.0 million kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase angle of 155 degrees. Image scale is 4 miles (6 kilometers) per pixel.

See a larger version of this image here from NASA.

October 30, 2015December 23, 2015 by David Dickinson

Images from Enceladus ‘Plume Dive’ Courtesy of Cassini

Oh, to hitch a ride aboard NASA’s Cassini spacecraft this week. The Saturn orbiting sentinel recently completed an amazing series of passes near the enigmatic ice-covered moon Enceladus, including a daredevil dive only 49 km (31 miles) above the southern pole of the moon and through an ice geyser. Images of the dramatic flyby were released by the Cassini team earlier this morning, revealing the moon in stunning detail.

“Cassini’s stunning images are providing us a quick look at Enceladus from this ultra-close flyby, but some of the most exciting science is yet to come,” says NASA mission project scientist Linda Spilker in today’s NASA/JPL press release.

Launched in 1997 from Cape Canaveral Florida in a dramatic night shot, Cassini arrived at the Saturnian system in 2004, and has delivered on some amazing planetary science ever since.

Discovered in 1789 by William Herschel, we got our very first views of Enceladus via the Voyager 1 spacecraft at 202,000 kilometers distant in 1980. Cassini has flown by the moon 21 times over the past decade, and ice geysers were seen sprouting from the surface of the moon by Cassini on subsequent flybys. one final flyby of Enceladus is planned for this coming December.

Mission planners are getting more daring with the spacecraft as its mission nears completion in 2017. The idea of reaching out and ‘tasting’ an icy plume emanating from Enceladus has been an enticing one, though a fast-moving good-sized ice pellet could spell disaster for the spacecraft.

NASA successfully established contact with the spacecraft on Wednesday night October 28^th after the closest approach for the flyby at 11:22 AM EDT/ 15:22 UT (Universal Time) earlier in the day. Cassini is reported to be in good health, and we should see further images along with science data returns in the weeks to come.

A second, more distant flyby of Enceladus was completed by Cassini earlier this month as it passed 1,142 miles (1,839 kilometers) from the northern pole of Enceladus on October 14^th, 2015 on its E-20 flyby.

But beyond just pretty post-cards from the outer solar system, Cassini’s successive passes by the mysterious moon will characterize just what might be occurring far down below.

Why Enceladus? Well, ever since ice geysers were spotted gushing from the fractured surface of the moon, it’s been on NASA’s short list of possible abodes for life in the solar system. Other contenders include Mars, Jupiter’s moon Europa, and Saturn’s giant moon, Titan. If the story of life on Earth is any indication, you need a place where an abundant level of chemical processes are occurring, and a subsurface ocean under the crust of Enceladus heated by tidal flexing may just fit the bill.

We’ll be adding further images and info to this post as more data comes in over the weekend, plus Cassini mission highlights, a look at the mission and final objectives and the last days of Cassini and more…

Stay tuned!

The end of Cassini in 2017 as it burns up in the atmosphere of Saturn will be a bittersweet affair, as our outer solar system eyes around the ringed planet fall silent. Cassini represents the most distant spacecraft inserted into orbit around a planet, and ESA’s Huygens lander on Titan marked the most remote landing on another world as well. Will we one day see a Titan Blimp or Ocean Explorer, or perhaps a dedicated life-finding mission to Enceladus? Final mission objectives for NASA’s Cassini spacecraft include a final flyby of Saturn’s large moon Titan, which will set the course for its final death plunge into the atmosphere of Saturn on September 15^th, 2017.

A high-resolution capture of Enceladus released this weekend by the Cassini team. The spacecraft was about 60,000 miles (96,000 kilometers) out when this image was taken. You can see the stark contract of the moon's fractured cantlope terrain, versus craters in the opposite hemisphere imaged criedt: NASA/JPL-CalTech/Space Science Institute — A high-resolution capture of Enceladus released this weekend by the Cassini team. The spacecraft was about 60,000 miles (96,000 kilometers) out when this image was taken. You can see the stark contract of the moon’s fractured cantaloupe terrain, versus craters in the opposite hemisphere imaged. Credit: NASA/JPL-CalTech/Space Science Institute

Want to see Enceladus for yourself? The moon orbits Saturn once every 1.4 days, reaching a maximum elongation of 13″ from the ring tips of Saturn and a maximum brightness of magnitude +11.7. Enceladus is one of six major moons of Saturn visible in a backyard telescope, and one of 62 moons of the ring planet known overall. The other five moons within reach of an amateur telescope are: Titan, Mimas, Dione, Rhea, and Tethys, and the fainter moon Hyperion shining at magnitude +15 might just be within reach of skill observers with large light bucket instruments.

Enjoy the amazing views of Enceladus, courtesy of Cassini!

October 15, 2015December 23, 2015 by Nancy Atkinson

Cassini’s Close Flyby of Enceladus Yields Surprising, Perplexing Imagery

Craters near Enceladus' north pole region appear to be 'melting' into each other. Image taken by Cassini spacecraft on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute

If you thought Saturn’s moon Enceladus couldn’t get any more bizzare — with its magnificent plumes, crazy tiger-stripe-like fissures and global subsurface salty ocean — think again. New images of this moon’s northern region just in from the Cassini spacecraft show surprising and perplexing features: a tortured surface where craters look like they are melting, and fractures that cut straight across the landscape.

“We’ve been puzzling over Enceladus’ south pole for so long, time to be puzzled by the north pole!” tweeted NASA engineer Sarah Milkovich, who formerly worked on the Cassini mission.

While the Cassini mission has been at the Saturn system since 2004 and flown by this moon several times, this is the spacecraft’s first close-up look at the north polar region of Enceladus. On October 14, 2015 the spacecraft passed at an altitude of just 1,839 kilometers (1,142 miles) above the moon’s surface.

See more imagery below:

Craters and a possible straight fracture line mar the surface of Enceladus in this raw image from the Cassini spacecraft taken on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute.

The reason Cassini hasn’t been able to see the northern terrain of Enceladus previously is that it was concealed by the darkness of winter. It’s now summer in the high northern latitudes, and scientists have been anxious to take a look at this previously unseen region. Gauging by the posts of “Wow!” and “Enceladus what are you doing??” by scientists on social media, the Cassini team is as excited and perplexed by these images as the rest of us.

“We’ve been following a trail of clues on Enceladus for 10 years now,” said Bonnie Buratti, a Cassini science team member and icy moons expert at NASA’s Jet Propulsion Laboratory. “The amount of activity on and beneath this moon’s surface has been a huge surprise to us. We’re still trying to figure out what its history has been, and how it came to be this way.”

Craters and fractures dot the landscape of the northern region of Enceladus in this raw image from the Cassini spacecraft taken on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute.

While these raw images just arrived this morning, already image editing enthusiasts have dived into the data to create composite and color images. Here are two from UT writer Jason Major and image contributor Kevin Gill:

A beautiful view of the night side of a crescent Enceladus, lovingly lit by Saturnshine. This was captured by the Cassini spacecraft during a close pass on Oct. 14, 2015. The 6.5-mile-wide Bahman cater is visible near the center. Credit: NASA/JPL-Caltech/Space Science Institute, image editing by Jason Major.

Saturn's icy moon Enceladus on October 14th, 2015 during Cassini's latest encounter. Assembled from uncalibrated images using infrared, green, and ultraviolet light. Image Credit: NASA/JPL-CalTech/ISS/Kevin M. Gill — Saturn’s icy moon Enceladus on October 14th, 2015 during Cassini’s latest encounter. Assembled from uncalibrated images using infrared, green, and ultraviolet light. Image Credit: NASA/JPL-CalTech/ISS/Kevin M. Gill

In an email, Cassini imaging team leader Carolyn Porco explained the flyby: “Our cameras were active during most of this encounter, allowing the imaging team and other remote-sensing instrument teams to observe the Saturn-opposing side of Enceladus on the inbound leg of the encounter, and a narrow, sunlit crescent outbound.”

From previous imagery and study of this moon, it has been suggested that the fractured and wrinkled terrain on Enceladus could be the scars of a shift in the moon’s spin rate. The moon has likely undergone multiple episodes of geologic activity spanning a considerable portion of its lifetime.

A complex region of craters and fractures near the north polar region on Saturn's moon Enceladus. Image from Cassini spacecraft taken on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute — A complex region of craters and fractures near the north polar region on Saturn’s moon Enceladus. Image from Cassini spacecraft taken on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute

While these images are incredible, get ready for even more. An even closer flyby of Enceladus is scheduled for Wednesday, Oct. 28, during which Cassini will come dizzyingly close to the icy moon, passing just 49 kilometers (30 miles) above the moon’s south polar region. NASA says that during this encounter, Cassini will make its deepest-ever dive through the moon’s plume of icy spray, collecting images and valuable data about what’s going on beneath the frozen surface. Cassini scientists are hopeful data from that flyby will provide evidence of how much hydrothermal activity is occurring in the moon’s ocean, and how the amount of activity impacts the habitability of Enceladus’ ocean.

Then another flyby — Cassini’s final scheduled close flyby of Enceladus — on Dec. 19 will examine how much heat is coming from the moon’s interior from an altitude of 4,999 kilometers (3,106 miles).

Enceladus hovers over Saturn's rings in this raw image from the Cassini spacecraft taken on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute. — Enceladus hovers over Saturn’s rings in this raw image from the Cassini spacecraft taken on October 14, 2015. Credit: NASA/JPL-Caltech/Space Science Institute.

An interesting side note is that the Cassini mission launched 18 years ago today (October 15, 1997).

Again stay tuned for more, and you can see all of Cassini’s raw image here, and find out more details of the upcoming flybys at this CICLOPS page.