Cassini Archives

December 12, 2013December 23, 2015 by Nancy Atkinson

New Flyover Video Takes You on a Tour of Titan’s Lake Region

This colorized mosaic from NASA's Cassini mission shows the most complete view yet of Titan's northern land of lakes and seas. Saturn's moon Titan is the only world in our solar system other than Earth that has stable liquid on its surface. The liquid in Titan's lakes and seas is mostly methane and ethane. Image credit: NASA/JPL-Caltech/ASI/USGS

Saturn’s moon Titan has the only known liquid lakes beyond planet Earth, and new data from the Cassini spacecraft’s radar instrument provides an intriguing 3-D flyover of these hydrocarbon lakes and seas at the north pole region. Steve Wall, Cassini acting radar team lead, provided a guided tour as he presented the video at the American Geophysical Union conference in San Francisco, noting that the vertical heights are exaggerated tenfold and the data has been colorized, both for visual effect.

The video starts by zooming into the southern end of Kraken Mare, the largest of Titan’s seas, and as you fly a little farther, Wall said the things that look like little islands are just noise in the radar data. Next, comes Ligea Mare, with its rugged coastline, and you’ll see that the liquid flow into the surrounding terrain, which appear like river valleys.

The “smooth” area that stretches farther from Ligea Mare is actualy not so smooth, but is just an area when the science team doesn’t have topographical data yet.

The video then continues to other smaller lakes that are nestled into valleys and rugged terrain.

“Learning about surface features like lakes and seas helps us to understand how Titan’s liquids, solids and gases interact to make it so Earth-like,” said Wall. “While these two worlds aren’t exactly the same, it shows us more and more Earth-like processes as we get new views.”

The new data is not only visually stunning, but provides previously unknown details about these lakes and the region. For example, Kraken Mare is more extensive and complex than previously thought. They also show nearly all of the lakes on Titan fall into an area covering about 600 miles by 1,100 miles (900 kilometers by 1,800 kilometers). Only 3 percent of the liquid at Titan falls outside of this area.

“Scientists have been wondering why Titan’s lakes are where they are. These images show us that the bedrock and geology must be creating a particularly inviting environment for lakes in this box,” said Randolph Kirk, a Cassini radar team member at the U.S. Geological Survey in Flagstaff, Ariz. “We think it may be something like the formation of the prehistoric lake called Lake Lahontan near Lake Tahoe in Nevada and California, where deformation of the crust created fissures that could be filled up with liquid.”

Additionally, scientists now know that Ligeia Mare is about 560 feet (170 meters) deep. This is the first time scientists have been able to plumb the bottom of a lake or sea on Titan. This was possible partly because the liquid turned out to be very pure, allowing the radar signal to pass through it easily. The liquid surface may be as smooth as the paint on our cars, and it is very clear to radar eyes.

“Ligeia Mare turned out to be just the right depth for radar to detect a signal back from the sea floor, which is a signal we didn’t think we’d be able to get,” said Marco Mastrogiuseppe, a Cassini radar team associate at Sapienza University of Rome. “The measurement we made shows Ligeia to be deeper in at least one place than the average depth of Lake Michigan.”

The new results indicate the liquid is mostly methane, somewhat similar to a liquid form of natural gas on Earth.

Sources: AGU press conference, JPL press release

December 5, 2013December 23, 2015 by Elizabeth Howell

Saturn’s Mysterious Hexagon Behaves Like Earth’s Ozone Hole

At Saturn, NASA's Cassini spacecraft snapped pictures showing a high-resolution view of a hexagon-shaped jet stream. Credit: NASA/JPL-Caltech/SSI/Hampton

A raging hurricane is creating a “suck zone” at Saturn’s north pole. The handy Cassini spacecraft recently captured a bunch of images of the six-sided jet stream surrounding the storm, which mission managers then put together into an awesome animation showing the wind currents shifting. (You can see the animation below the jump.)

The feature is pretty in a picture, but NASA has a special interest because there is nothing else like this anywhere in our solar system, the agency stated. The immense storm stretches 20,000 miles (30,000 kilometers) across with winds whipping in its jet stream at 200 miles per hour (322 kilometers per hour). And despite all the turbulence, the storm is staying put at the north pole for reasons scientists are still trying to understand.

“The hexagon is just a current of air, and weather features out there that share similarities to this are notoriously turbulent and unstable,” said Andrew Ingersoll, a Cassini imaging team member at the California Institute of Technology in Pasadena. “A hurricane on Earth typically lasts a week, but this has been here for decades — and who knows — maybe centuries.”

An animation of Cassini Saturn images showing a hexagonal jet stream surrounding a storm at the north pole. Credit: NASA/JPL-Caltech/SSI/Hampton University

Cassini has been orbiting Saturn since 2004, but it’s only since last year that it’s been able to peer at the hexagon with much success. That’s because the angle of the sun is finally favorable to peer at the storm. This has allowed scientists, for example, to look at the types of particles inside. They discovered that the jet stream is a sort of barrier around the storm, delineating a location with a lot of small haze particles and few large haze particles. (It’s the opposite outside of the jet stream). Scientists said it looks like the Antarctic ozone hole on Earth.

“The Antarctic ozone hole forms within a region enclosed by a jet stream with similarities to the hexagon,” NASA stated.

“Wintertime conditions enable ozone-destroying chemical processes to occur, and the jet stream prevents a resupply of ozone from the outside. At Saturn, large aerosols cannot cross into the hexagonal jet stream from outside, and large aerosol particles are created when sunlight shines on the atmosphere. Only recently, with the start of Saturn’s northern spring in August 2009, did sunlight begin bathing the planet’s northern hemisphere.”

Should Cassini have enough funding to function for a few more years, scientists are eager to watch as Saturn gets to its summer solstice in 2017 and the lighting gets even better around the north pole.

NASA also held an interesting Google+ Hangout yesterday (Nov. 4) about Saturn and the Cassini mission that featured Carolyn Porco, director of the Cassini Imaging Team and the Cassini Imaging Central Laboratory for Operations (CICLOPS). The whole video below is worth a watch, but here’s a little tidbit to let you know some of what was talked about:

“If you took all the mass of Saturn’s rings and recomposed it into a moon, it would be no bigger than Enceladus, so it’s a big spectacle coming from little mass,” Porco said. “The main rings are very thin, only about 30 feet [9 meters] thick, no bigger than about 2 stories in a modern day building. Despite the fact they are about 280,000 km [174,000 miles] across.”

December 3, 2013December 23, 2015 by Elizabeth Howell

Ghostly Pic Of Saturn’s Moon Shows It Rising From The Deep

Titan imaged by the Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute

Sunlight can do fun things in space. For example: this recent picture of Titan (a moon of Saturn) shows sunlight hitting the moon’s surface as well as a southern vortex, just visible in the shadows of the picture.

“The sunlit edge of Titan’s south polar vortex stands out distinctly against the darkness of the moon’s unilluminated hazy atmosphere,” NASA stated. “The Cassini spacecraft images of the vortex led scientists to conclude that its clouds form at a much higher altitude — where sunlight can still reach — than the surrounding haze.”

Titan has intrigued scientists for decades, since the Voyager spacecraft first revealed it as a world socked in by orange haze. Cassini dropped off a lander on the surface, called Huygens, which took pictures on the surface in 2005. Besides that, the orbiter has revealed a lot about lakes, rain and other features of the moon in the year since.

Cassini has been orbiting the moon since 2004 and is still busily producing science, but there are concerns that NASA’s budget situation could cause the agency to shut down operations on the still-healthy spacecraft. There are no other missions to Saturn or Titan booked yet, although scientists do have intriguing ideas for exploration.

November 21, 2013December 23, 2015 by David Dickinson

NASA Halts Work on its New Nuclear Generator for Deep Space Exploration

MSL's MMRTG in the laboratory. (Credit: NASA).

Another blow was dealt to deep space exploration this past weekend. The announcement comes from Jim Green, NASA’s Planetary Science Division Director. The statement outlines some key changes in NASA’s radioisotope program, and will have implications for the future exploration of the outer solar system.

An Advanced Stirling Converter prototype in the laboratory. (Credit: NASA).

We’ve written about the impending plutonium shortage and what it means for the future of spaceflight, as well as the recent restart of plutonium production. NASA is the only space agency that has conducted missions to the outer planets — even the European Space Agency’s Huygens lander had to hitch a ride with Cassini to get to Titan — and plutonium made this exploration possible. Continue reading “NASA Halts Work on its New Nuclear Generator for Deep Space Exploration”

November 12, 2013December 23, 2015 by Jason Major

The Day the Earth Smiled: Saturn Shines in this Amazing Image from the Cassini Team

The "pale blue dot" of Earth as seen from Cassini on July 19, 2013.

This summer, for the first time ever, the world was informed that its picture was going to be taken from nearly a billion miles away as the Cassini spacecraft captured images of Saturn in eclipse on July 19. On that day we were asked to take a moment and smile and wave at Saturn, from wherever we were, because the faint light from our planet would be captured by Cassini’s camera, shielded by Saturn from the harsh glare of the Sun.

A few preliminary images were released just a few days later showing the “pale blue dot” of Earth nestled within the glowing bands of Saturn’s rings. It was an amazing perspective of our planet, and we were promised that the full mosaic of Cassini images was being worked on and would be revealed in the fall.

Well, it’s fall, and here it is:

The full mosaic from the Cassini imaging team of Saturn on July 19, 2013... the "Day the Earth Smiled" — The full mosaic from the Cassini imaging team of Saturn on July 19, 2013… the “Day the Earth Smiled”

Simply beautiful!

Cassini Imaging Team leader Carolyn Porco wrote on her Facebook page:

“After much work, the mosaic that marks that moment the inhabitants of Earth looked up and smiled at the sheer joy of being alive is finally here. In its combination of beauty and meaning, it is perhaps the most unusual image ever taken in the history of the space program.”

Download a full-size version here.

Earth and Moon seen by Cassini on July 19, 2013

In this panorama of the Saturnian system, a view spanning 404,880 miles (651,591 km), we see the planet silhouetted against the light from the Sun. It’s a unique perspective that highlights the icy, reflective particles that make up its majestic rings and also allows our own planet to be seen, over 900 million miles distant. And it’s not just Earth that was captured, but the Moon, Venus, and Mars were caught in the shot too.

According to the description on the CICLOPS page, “Earth’s twin, Venus, appears as a bright white dot in the upper left quadrant of the mosaic… between the G and E rings. Mars also appears as a faint red dot embedded in the outer edge of the E ring, above and to the left of Venus.”

This was no simple point-and-click. Over 320 images were captured by Cassini on July 19 over a period of four hours, and this mosaic was assembled from 141 of those images. Because the spacecraft, Saturn, and its moons were all in constant motion during that time, affecting not only positions but also levels of illumination, imaging specialists had to adjust for that to create the single image you see above. So while all elements may not be precisely where they were at the same moment in time, the final result is no less stunning.

“This version was processed for balance and beauty,” it says in the description. (And I’ve no argument with that.)

See below for an annotated version showing the position of all visible objects, and read the full article on the CICLOPS page for an in-depth description of this gorgeous and historic image.

“I hope long into the future, when people look again at this image, they will recall the moment when, as crazy as it might have seemed, they were there, they were aware, and they smiled.”

–Carolyn Porco, Cassini Imaging Team Leader

Also, check out another version of this image from NASA made up of submitted photos from people waving at Saturn from all over the world. (Full NASA press release here.)

All images credit NASA/JPL-Caltech/Space Science Institute

UPDATE 11/13: CICLOPS Director Carolyn Porco describes how this image was acquired and assembled in this interview video from the World Science Festival:

November 5, 2013December 23, 2015 by Elizabeth Howell

Five Saturn Moons Stun In Cassini Spacecraft Archival Image

Saturn's moons (from left to right) Janus, Pandora, Enceladus, Mimas and Rhea. Rhea is on top of Saturn. Credit: NASA/JPL-Caltech/Space Science Institute

This picture is from a couple of years ago, but still worth the extra look. The Cassini spacecraft — busily circling Saturn and gathering data on the ringed planet and its moons — managed to grab five of Saturn’s 62 known moons in one shot. The European Space Agency highlighted the picture on its home page this week.

From left to right, you can see Janus, Pandora, Enceladus, Mimas and Rhea. Don’t be fooled by the rings near Rhea; those are actually Saturn’s rings. Rhea is just blocking the view of the planet from Saturn’s perspective during this picture portrait, which was taken on July 29, 2011.

The cornucopia of moons around Saturn is part of what makes that particular planet so interesting. Titan, the largest, is perhaps the most well-known because of its strange orange haze that intrigued astronomers when the twin Voyager spacecraft zoomed through the system in the 1980s. Cassini arrived in 2004 and revealed many more moons to science for the first time.

Color-composite of Titan made from raw Cassini images acquired on April 13, 2013 (added 4/17) NASA/JPL/SSI. Composite by J. Major.

“The dozens of icy moons orbiting Saturn vary drastically in shape, size, surface age and origin. Some of these worlds have hard, rough surfaces, while others are porous bodies coated in a fine blanket of icy particles. All have greater or smaller numbers of craters, and many have ridges and valleys,” NASA wrote on a web page about Saturn’s moons.

“Some, like Dione and Tethys, show evidence of tectonic activity, where forces from within ripped apart their surfaces. Many, like Rhea and Tethys, appear to have formed billions of years ago, while others, like Janus and Epimetheus, could have originally been part of larger bodies that broke up. The study and comparison of these moons tells us a great deal about the history of the Saturn System and of the solar system at large.”

And new discoveries are coming out all the time. Earlier this year, for example, astronomers said that the moon Dione could have had active geysers coming from its surface, such as what is likely happening on Enceladus.

October 23, 2013April 4, 2016 by Jason Major

Titan’s North Pole is Loaded With Lakes

Titan's north pole is home to many methane lakes. Credit: NASA

A combination of exceptionally clear weather, the steady approach of northern summer, and a poleward orbital path has given Cassini — and Cassini scientists — unprecedented views of countless lakes scattered across Titan’s north polar region. In the near-infrared mosaic above they can be seen as dark splotches and speckles scattered around the moon’s north pole. Previously observed mainly via radar, these are the best visual and infrared wavelength images ever obtained of Titan’s northern “land o’ lakes!”

Titan is currently the only other world besides Earth known to have stable bodies of liquid on its surface, but unlike Earth, Titan’s lakes aren’t filled with water — instead they’re full of liquid methane and ethane, organic compounds which are gases on Earth but liquids in Titan’s incredibly chilly -290º F (-180º C) environment.

While one large lake and a few smaller ones have been previously identified at Titan’s south pole, curiously almost all of Titan’s lakes appear near the moon’s north pole.

Infrared observations of Titan's northern lakes (NASA/JPL-Caltech/SSI) — Infrared observations of Titan’s northern lakes. The cross marks Titan’s geographic north pole. (NASA/JPL-Caltech/SSI)

For an idea of scale, the large lake at the upper right above (and the largest lake on Titan) Kraken Mare is comparative in size to the Caspian Sea and Lake Superior combined. Kraken Mare is so large that sunlight was seen reflecting off its surface in 2009. Punga Mare, nearest Titan’s pole, is 240 miles (386 km) across.

Besides revealing the (uncannily) smooth surfaces of lakes — which appear dark in near-infrared wavelengths but would also be darker than the surrounding landscape in visible light — these Cassini images also show an unusually bright terrain surrounding them. Since the majority of Titan’s lakes are found within this bright region it’s thought that there could be a geologic correlation; is this Titan’s version of karst terrain, like what’s found in the southeastern U.S. and New Mexico? Could these lakes be merely the visible surfaces of a vast underground hydrocarbon aquifer? Or are they shallow pools filling depressions in an ancient lava flow?

Annotated infrared mosaic of Titan's north pole (NASA/JPL-Caltech/SSI) — Annotated infrared mosaic of Titan’s north pole (NASA/JPL-Caltech/SSI)

Or, are they the remains of once-larger lakes and seas which have since evaporated? The orange-hued regions in the false-color mosaic may be evaporite — the Titan equivalent of salt flats on Earth. The evaporated material is thought to be organic chemicals originally from Titan’s haze particles that were once dissolved in liquid methane.

“Is this an indication that with increased warmth, the seas and lakes are starting to evaporate, leaving behind a deposit of organic material,” wrote Carolyn Porco, Cassini Imaging Team Leader, in an email earlier today. “…in other words, the Titan equivalent of a salt-flat?”

The largest lake at Titan’s south pole, Ontario Lacus, has been previously compared to such an ephemeral lake in Namibia called the Etosha Pan. (Read more here.)

These observations are only possible because of the extended and long-term study of Saturn and its family of moons by the Cassini spacecraft, which began with its establishing orbit in 2004 and has since continued across multiple seasons over a third of the ringed planet’s year. The existence of methane lakes on Titan is undoubtedly fascinating, but how deep the lakes are, where they came from and how they behave in Titan’s environment have yet to be discovered. Luckily, the changing season is on our side.

“Titan’s northern lakes region is one of the most Earth-like and intriguing in the solar system,” said Linda Spilker, Cassini project scientist, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We know lakes here change with the seasons, and Cassini’s long mission at Saturn gives us the opportunity to watch the seasons change at Titan, too. Now that the sun is shining in the north and we have these wonderful views, we can begin to compare the different data sets and tease out what Titan’s lakes are doing near the north pole.”

The images shown above were obtained by Cassini’s visual and infrared mapping spectrometer (VIMS) during a close flyby of Titan on Sept. 12, 2013.

Read more on the Cassini Imaging Central Laboratory for Operations (CICLOPS) site here and on the NASA site here.

“But how thrilling it is to still be uncovering new territory on this fascinating moon… a place that, until Cassini’s arrival at Saturn nearly 10 years ago, was the largest single expanse of unseen terrain we had remaining in our solar system. Our adventures here have been the very essence of exploration. And it’s not over yet!”

– Carolyn Porco on Facebook

An illustration of a Titanic lake by Ron Miller. All rights reserved. Used with permission. — An illustration of a Titanic lake © Ron Miller. All rights reserved.

Also, check out a corresponding article and intriguing illustration of robotic Titan exploration by space artist extraordinaire Ron Miller on io9.com.

October 17, 2013December 23, 2015 by Nancy Atkinson

An Incredible View of Saturn that Could Only Be Seen by a Visiting Spacecraft

Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute. Assembled by Gordan Ugarkovic. — Saturn and its rings, as seen from above the planet by the Cassini spacecraft. Credit: NASA/JPL/Space Science Institute/Gordan Ugarkovic

So what did NASA do during the US government shutdown? You can’t just turn off spacecraft that are operating millions of miles away, so missions like the Mars rovers and the Cassini spacecraft at Saturn continued to send back images to Earth during the 16 days that most of NASA wasn’t up and running like usual. On October 10, 2013, as Cassini flew high above the planet’s equatorial plane, the spacecraft’s camera took 36 images of Saturn, a dozen each using the various red, green, and blue filters used to create color images. The images were transferred back to Earth and put on the Cassini raw images page. Gordan Ugarkovic from Croatia, and a member of the image editing wizards at UnmannedSpaceflight.com, grabbed the raw files, processed them, then assembled the images into this jaw-dropping mosaic.

This is a view from Saturn that we could never get from Earth; only a spacecraft orbiting the planet could take it. You can see the north pole and the swirling maelstrom of clouds that creates the hexagonal polar vortex, the thin bands in Saturn’s atmosphere, and — of course — what really stands out is the incredible view of Saturn’s rings. To see the original 3 MB version, see this page on UMSF.

“You shouldn’t be surprised to see processing artifacts here and there,” cautioned Ugarkovic via email to Universe Today. “It is, after all, based on raw JPEG images only.”

See more of Gordan’s work at his Flickr page.

You can read more details about this from Emily Lakdawalla at the Planetary Society, or Phil Plait at Bad Astronomy/Slate.

But in the words of UMSF’s Astro0, “That’s the sort of view I’ve dreamed I would only ever see in a science fiction movie or if we had some kind of amazing futuristic spacecraft orbiting around that distant ringed planet….WAIT! We do!”

For more of what NASA did during the shutdown, Bill Dunford at Riding With Robots put together a great summary, quoting the @SarcasticRover that “You can’t shut down awesome.” Bill started the #ThingsNASAMightTweet hashtag that reminded everyone of all the things NASA does, but they couldn’t tweet about during the shutdown. People from around the world chimed in, adding what was important to them about NASA, and as of today, tweets with that hashtag have passed 27 million impressions.

September 24, 2013December 23, 2015 by Nancy Atkinson

Enceladus, Afterburners Still Firing

This view of Saturn's moon Enceladus and its prominent plumes was taken by the Cassini spacecraft on April 2, 2013. Credit: NASA/JPL-Caltech/Space Science Institute.

We can never get enough of seeing those intriguing jets and plumes from Saturn’s moon Enceladus, especially this great view from the Cassini spacecraft where the plumes are back-it from the Sun while the moon’s surface is lit with reflected light from Saturn. And as you can see, those jets are still firing. There are close to 100 geyser jets of varying sizes near Enceladus’s south pole spraying water vapor, icy particles, and organic compounds out into space. If you look closely, you’ll see the entire plume is as large as the moon itself.

Can we please send another spacecraft just to study this fascinating moon?

The image was taken in blue light with the Cassini spacecraft narrow-angle camera on April 2, 2013, when Cassini was about 517,000 miles (832,000 kilometers) from Enceladus.

See more details at the Cassini website.

September 17, 2013December 23, 2015 by Jason Major

A “Mini Jet” Juts from Saturn’s F Ring

A bright "mini-jet" spotted in Saturn's F ring

We all know that Saturn’s moon Enceladus has a whole arsenal of geysers jetting a constant spray of ice out into orbit (and if you didn’t know, learn about it here) but Enceladus isn’t the only place in the Saturnian system where jets can be found — there are some miniature versions hiding out in the thin F ring as well!

Watch the 50-mile-wide Prometheus dip into the F ring (CLICK TO PLAY) NASA/JPL/SSI. Animation by J. Major.

The image above, captured by the Cassini spacecraft on June 20, 2013, shows a segment of the thin, ropy F ring that encircles Saturn just beyond the A ring (visible at upper right). The bright barb near the center is what scientists call a mini jet, thought to be caused by small objects getting dragged through the ring material as a result of repeated passings by the shepherd moon Prometheus.

Coincidentally, it’s gravitational perturbations by Prometheus that help form the objects — half-mile-wide snowball-like clusters of icy ring particles — in the first place.

Unlike the dramatic jets on Enceladus, which are powered by tidal stresses that flex the moon’s crust, these mini jets are much more subtle and occur at the casual rate of 4 mph (2 meters/second)… about the speed of a brisk walk.

The reflective jets themselves can be anywhere from 25 to 112 miles (40 to 180 kilometers) long.

See more images of mini jets — also called “classic trails” — below:

Various images of mini jets captured by Cassini from 2005 to 2008.

Over 500 of these features have been imaged by Cassini since 2005. Read more about mini jets here.

(And don’t worry, Enceladus… these little jets are interesting but they have nothing on you!)

Source: Cassini Imaging Central Laboratory for OPerationS (CICLOPS)

Image credits: NASA/JPL-Caltech/SSI/QMUL.