Tag Archives: cassini

Titan’s largest methane sea is over 1000 feet deep, says a new paper

Titan’s seas should be deep enough for a robotic submarine to wade through, a new paper explains. This should help pave the way towards our exploration of Titan’s depths.

Radar map of the polar region of Saturn’s moon Titan. Image credits NASA / JPL-Caltech.

Fancy a dip? Who doesn’t. But if you ever find yourself on Titan, Saturn’s biggest moon, you should stay away from swimming areas. A new paper reports that the Kraken Mare, the largest body of liquid methane on the moon’s surface is at least 1,000 feet deep near its center, making it both very deep and very cold.

While that may not be very welcoming to humans, such findings help increase our confidence in plans of exploring the moon’s oceans using autonomous submarines. It was previously unknown if Titan’s methane seas were deep enough to allow such a craft to move through.

Faraway seas

“The depth and composition of each of Titan’s seas had already been measured, except for Titan’s largest sea, Kraken Mare—which not only has a great name, but also contains about 80% of the moon’s surface liquids,” said lead author Valerio Poggiali, a research associate at the Cornell Center for Astrophysics and Planetary Science (CCAPS).

Titan is a frozen moon that shines with a golden haze as sunlight glints on its nitrogen-rich atmosphere. Beyond that, however, it looks surprisingly Earth-like with liquid rivers, lakes, and seas sprawling along its surface. But these are not made of water — they’re filled with ultra-cold liquid methane.

The findings are based on data from one of the last Titan flybys made during the Cassini mission (on Aug. 21, 2014). During this flyby, the probe’s radar was aimed at Ligeia Mare, a smaller sea towards the moon’s northern pole. Its goal was to understand the mysterious “Magic Island” that keeps disappearing and then popping back up again.

Its radar altimeter measured the liquid depth at Kraken Mare and Moray Sinus (an estuary on the sea’s northern shore). The authors of the paper, made up of members from both NASA’s Jet Propulsion Laboratory and Cornell University, used this data to map the bathymetry (depth) of the sea. They did this by tracking the return time on the radar’s signal for the liquid’s surface and the sea bottom while taking into account the methane’s effect on the signal (it absorbs some of the energy from the radio wave as it passes through, in essence dampening it to an extent).

Colorized mosaic of Titan’s Kraken Mare. Liquids are blue and black, land areas appear yellow to white. The surface was mapped using radar data from NASA’s Cassini. Image credits NASA / JPL-Caltech / Agenzia Spaziale Italiana / USGS via Wikimedia.

According to them, the Moray Sinus is about 280 feet deep, and the Kraken Mare gets progressively deeper towards its center. Here, the sea is too deep for the radar signal to pierce through, so we don’t know its maximum depth. The data also allowed us some insight into the chemical composition of the sea: a mix of ethane and methane, dominated by the latter. This is similar to the chemical composition of Ligeia Mare, Titan’s second-largest sea, the team explains. It might seem inconsequential, but it’s actually a very important piece of information: it suggests that Titan has an Earth-like hydrologic system.

Kraken Mare (‘mare’ is Latin for ‘sea’) is our prime choice for a Titan-scouting submarine due to its size — it is around as large as all five of America’s Great Lakes put together. We also have no idea why this sea doesn’t just evaporate. Sunlight is about 100 times less intense on Titan than Earth, but it’s still enough to make the methane evaporate. According to our calculations, this process should have completely depleted the seas in around 10 million years, but evidently, that didn’t happen. This is yet another mystery our space-faring submarine will try to answer.

“Thanks to our measurements,” he said, “scientists can now infer the density of the liquid with higher precision, and consequently better calibrate the sonar aboard the vessel and understand the sea’s directional flows.”

The paper “The Bathymetry of Moray Sinus at Titan’s Kraken Mare” has been published in the journal Journal of Geophysical Research: Planets.

How Enceladus got its stripes

First seen by the Cassini mission to Saturn, Enceladus’ “tiger stripes” are, to the best of our knowledge, unique in our Solar System. This false-color image from the Cassini mission shows the fissures in blue. Image credits: NASA / JPL.

Enceladus is one of the stranger bodies in our solar system. It’s a frozen, barren satellite, orbiting Saturn, with not much going on about it — or so it would seem at a first glance.

Like Europa, Enceladus is also believed to host an ocean of subsurface water, with hydrothermal vents sending massive jets of water into space. Given that its chemistry is rich in salts, silicates, and iron, it could very well host the ingredients necessary for life to emerge. The Cassini mission also found traces of simple and complex organic molecules (such as benzene) around Enceladus.

With this alone, Enceladus has become one of the most interesting spots in our solar system. But that’s not its only trick.

Slashed across its south pole are four straight, parallel fissures where water erupts. These “tiger stripes” are unlike anything we’ve seen in the solar system. We don’t know how they were formed and why they exist in the first place. To make matters even more mysterious, they only lie in the southern hemisphere and are spaced at even distances.

“We want to know why the eruptions are located at the south pole as opposed to some other place on Enceladus, how these eruptions can be sustained over long periods of time and finally why these eruptions are emanating from regularly spaced cracks,” said Max Rudolph, assistant professor of earth and planetary sciences at the University of California, Davis.

Now, researchers at UC Davis, the Carnegie Institution and UC Berkeley believe they have an explanation. Using numerical modeling, they explain that tidal heating is responsible for the fissures and their unusual distribution.

“First seen by the Cassini mission to Saturn, these stripes are like nothing else known in our Solar System,” lead author Hemingway explained. “They are parallel and evenly spaced, about 130 kilometers long and 35 kilometers apart. What makes them especially interesting is that they are continually erupting with water ice, even as we speak. No other icy planets or moons have anything quite like them.”

They found that there’s no particular reason why the stripes emerged in the southern hemisphere — they could have emerged in any one half, it was a coin toss — and it just happened to be the southern one.

As it orbits Saturn, Enceladus’ internal structure is tidally drawn to the planet. Just like the Earth’s seas experience low tide and high tide due to gravitational attraction by the moon, Enceladus’ ice, water, and rocky core are tidally drawn to Saturn. This force creates a lot of friction, which in turn produces heat — this is the reason why Enceladus isn’t completely frozen and has liquid water beneath its surface, despite being so far away from the sun.

But due to its eccentric orbit, Enceladus is sometimes closer to Saturn, and other times a little farther away — which causes the moon to be slightly deformed. This means that in some regions, more water warms and becomes liquid, while in other parts, the opposite process takes place. As liquid water solidifies under the shell, it expands in volume, putting pressure on the surface ice; when this happens and enough force is exerted, the ice simply cracks.

The tiger stripes are essentially the Enceladus version of stretch marks.

The researchers modeled this phenomenon and found that it also explains why the stripes are spread evenly.

“That caused the ice sheet to flex just enough to set off a parallel crack about 35 kilometers away,” Rudolph added.

But it gets even more interesting. The surface of Enceladus is approximately -200 degrees Celsius cold — so it’s cold enough to freeze back in place quite quickly. The continuous tidal forces would constantly generate cracks, but it would be a dynamic stretching-healing process, which does not seem to be the case. Instead, the stability of the cracks indicates that they stretch all the way down to the liquid ocean below.

In addition, if the moon was a bit larger, its own gravity would be strong enough to prevent the fractures from opening all the way down — so these stripes could have only formed on Enceladus, researchers conclude.

“Since it is thanks to these fissures that we have been able to sample and study Enceladus’ subsurface ocean, which is beloved by astrobiologists, we thought it was important to understand the forces that formed and sustained them,” Hemingway said. “Our modeling of the physical effects experienced by the moon’s icy shell points to a potentially unique sequence of events and processes that could allow for these distinctive stripes to exist.”

Saturn.

Planetary rings are surprisingly chemically-rich, paper reports

Saturn’s rings are very chemically complex, new research shows, and actively change the makeup of the planet’s atmosphere.

Saturn.

Titan in front of Saturn and its rings.
Image credits NASA / JPL-Caltech / Space Science Institute.

Data beamed back from the Cassini spacecraft during its final descent into the depths of Saturn shows that the giant’s rings are more chemically complex than we’ve believed.

If you like it, study the rings on it

“This is a new element of how our solar system works,” said Thomas Cravens, professor of physics & astronomy at the University of Kansas and a co-author of the new paper.

Cravens is a member of Cassini’s Ion and Neutral Mass Spectrometer (INMS) team. Back in 2017, as Cassini plunged into Saturn’s upper atmosphere, it sampled the chemical makeup of points at various altitudes between Saturn’s rings and atmosphere using its onboard mass spectrometer.

The paper reports finding a surprising chemical complexity in the planet’s rings. This challenges the current view, based on past observations, that the rings “would be almost entirely water”, Cravens explains.

“Two things surprised me. One is the chemical complexity of what was coming off the rings — we thought it would be almost entirely water based on what we saw in the past. The second thing is the sheer quantity of it — a lot more than we originally expected.”

“the mass spectrometer saw methane — no one expected that. Also, it saw some carbon dioxide, which was unexpected,” Cravens explains. “The rings were thought to be entirely water. But the innermost rings are fairly contaminated, as it turns out, with organic material caught up in ice.”

The INMS-readings were performed in the gap between the inner ring and upper atmosphere. They uncovered the presence of water, methane, ammonia, carbon monoxide, molecular nitrogen, and carbon dioxide in the rings.

Dust grains from Saturn’s D (innermost) ring constantly rain down into the planet’s upper atmosphere, carrying a coating of this ‘chemical cocktail’. This process takes place at an extraordinary rate, the team adds — 10 times faster than previously estimated. This process is powered by the different spin rates of the planet and its rings (the rings spin faster than the planet’s atmosphere). Over time, this process likely changed the carbon and oxygen content of Saturn’s atmosphere.

“We saw it was happening even though it’s not fully understood,” Cravens adds. “What we saw is this material, including some benzine, was altering the uppermost atmosphere of Saturn in the equatorial region. There were both grains and dust that were contaminated.”

The findings not only shed light on the chemical complexity of planetary rings, but also raise important questions pertaining to their formation, lifespan, and interaction with the host planet.

For example, given the very high rate of material transfer to the atmosphere, it may be safe to assume that planetary rings are much more short-lived than previously estimated. In the absence of a source of fresh material to make up for this particle flow, rings may simply drain away into nothingness. One possibility that derives from these findings is that Jupiter likely also had its own set of fully-fleshed out rings, which gradually drained into the wispy trail that surrounds the gas giant today.

The origin of these complex materials is also of interest to astronomers; “[is material in the rings] left over from the formation of our solar system? Does it date back to proto pre-solar nebula, the nebula that collapsed out of interstellar media that formed the sun and planets?”

Finally, the team reports that this influx of matter also impacts the planet’s ionosphere by converting hydrogen ions and triatomic hydrogen ions into heavier molecular ions — thereby depleting the ionosphere of charged particles.

But Cravens’ main contribution involved interpreting that data with a focus on how materials from the rings are altering Saturn’s ionosphere.

“My interest was in the ionosphere, the charged-particle environment, and that’s what I focused on,” Cravens said. “This gunk coming in chews up a lot of the ionosphere, affects its composition and causes observable effects — that’s what we’re trying to understand now. The data are clear, but explanations are still being modeled and that will take a while.”

The paper has been published in the journal Science.

Artist impression of a dust storm on Titan. Credit: IPGP/Labex UnivEarthS/University Paris Diderot – C. Epitalon & S. Rodriguez.

Scientists spot dust storms on Titan for the first time

Artist impression of a dust storm on Titan. Credit: IPGP/Labex UnivEarthS/University Paris Diderot – C. Epitalon & S. Rodriguez.

Artist impression of a dust storm on Titan. Credit: IPGP/Labex UnivEarthS/University Paris Diderot – C. Epitalon & S. Rodriguez.

Although Titan is a moon, it has an intriguing geology and, in many aspects, is very similar to Earth. Titan has a substantial atmosphere and is the only body in the solar system other than Earth to host stable liquid (in its case, methane) on its surface. Now, researchers have identified giant dust storms in equatorial regions of Saturn’s moon. This makes Titan the third object in the solar system, along with Earth and Mars, where such a meteorological phenomenon has been observed.

Dust storms on Titan

Titan has active weather that changes from season to season, particularly during the equinox — the time when the sun crosses Titan’s equator — when massive clouds of methane and ethane can cause powerful storms in the moon’s tropical regions.

[panel style=”panel-info” title=”Titan: a strange world” footer=””]Titan is the only known moon with a fully developed atmosphere that consists of more than just trace gases. Titan’s temperature is about 94 K (−179 °C, or −290.2 °F) at the surface. At this temperature, water ice does not sublimate from solid to gas, so the atmosphere is nearly free of water vapor. “You have all these things that are analogous to Earth. At the same time, it’s foreign and unfamiliar,” said Ray Pierrehumbert, the Louis Block Professor in Geophysical Sciences at Chicago.[/panel]

During its numerous flybys of Titan, NASA’s Cassini spacecraft recorded many such storms. However, on one occasion, it spotted three unusual equatorial brightenings with its infrared instruments. At the time, in 2009, scientists thought these were some kind of methane clouds — but a subsequent examination revealed that they were dealing with something totally different.

The features were not frozen methane rain or icy lavas, either, because they did not match the chemical signature and should have remained visible for much longer than the bright features observed in the study. These appeared for only 11 hours to five weeks.

Bright spots recorded in infraded by NASA’s Cassini mission between 2009 and 2010. Credit: NASA/JPL-Caltech/University of Arizona/University Paris Diderot/IPGP/S. Rodriguez et al. 2018.

Modeling of the bright features also showed that the features must be atmospheric but still close to the surface, forming a thin layer of solid organic particles. Finally, because the features were located right above dune fields on Titan’s equator, the authors of the new study concluded that the only viable explanation remaining was that the spots were actually clouds of dust.

“Titan is a very active moon,” said Sebastien Rodriguez, an astronomer at the Université Paris Diderot, France, and the paper’s lead author. “We already know that about its geology and exotic hydrocarbon cycle. Now we can add another analogy with Earth and Mars: the active dust cycle, in which organic dust can be raised from large dune fields around Titan’s equator.”

Nine Cassini flybys of Titan in 2009 and 2010 show three instances when clear bright spots suddenly appeared in images taken by the spacecraft’s Visual and Infrared Mapping Spectrometer. Credit: NASA/JPL-Caltech/University of Arizona/University Paris Diderot/IPGP/S. Rodriguez et al. 2018.

Titan’s dust probably forms when organic molecules, resulting from methane’s interaction with sunlight, grow large enough to fall to the surface. In fact, Rodriguez says that one of NASA’s probe that touched down on Titan raised dust upon its landing — a first hint that dust storms were occurring on Saturn’s moon.

“We believe that the Huygens Probe, which landed on the surface of Titan in January 2005, raised a small amount of organic dust upon arrival due to its powerful aerodynamic wake,” said Rodriguez. “But what we spotted here with Cassini is at a much larger scale. The near-surface wind speeds required to raise such an amount of dust as we see in these dust storms would have to be very strong—about five times as strong as the average wind speeds estimated by the Huygens measurements near the surface and with climate models.”

Dust storms on Titan imply that the moon’s giant dunes are still active and continually changing. Wind could be transporting dust from far-away regions, triggering a global cycle of organic dust on the moon.

Scientific reference: S. Rodriguez et al. Observational evidence for active dust storms on Titan at equinox, Nature Geoscience (2018). DOI: 10.1038/s41561-018-0233-2.

Enceladus interior.

Enceladus “the only body besides Earth to satisfy all of the basic requirements for life,” Cassini reveals

Data beamed back by the Cassini spacecraft reveals that Enceladus, Saturn’s sixth-largest moon, isn’t shy about blasting large organic molecules into space.

Enceladus interior.

Hydrothermal processes in the moon’s rocky core could synthesize organics from inorganic precursors. Alternatively, these processes could be transforming preexisting organics by heating, or they could even generate geochemical conditions in the subsurface ocean of Enceladus that would allow possible forms of alien life to synthesize biological molecules.
Image credits NASA/JPL-Caltech/Space Science Institute/LPG-CNRS/Nantes-Angers/ESA

Mass spectrometry readings beamed back by NASA’s Cassini craft show that Enceladus is bursting with organic molecules. The moon’s icy surface is pockmarked with deep cracks that spew complex, carbon-rich compounds into space. Scientists at the Southwest Research Institute (SwRI) say these compounds are likely the result of interactions between the moon’s rocky core and warm waters from its subsurface ocean.

Why so organic?

“We are, yet again, blown away by Enceladus,” said SwRI’s Dr. Christopher Glein, co-author of a paper describin the discovery.

“Now we’ve found organic molecules with masses above 200 atomic mass units. That’s over ten times heavier than methane. With complex organic molecules emanating from its liquid water ocean, this moon is the only body besides Earth known to simultaneously satisfy all of the basic requirements for life as we know it.”

The Cassini mission, a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency, is widely-held to be one of the most ambitious space exploration missions we’ve ever embarked upon. Launched on October 15, 1997, Cassini spent some 13 years studying the gas giant and its moons. The craft also flew by Venus (April 1998 and July 1999), Earth (August 1999), the asteroid 2685 Masursky, and Jupiter (December 2000), before settling in on Saturn’s orbit on July 1st, 2001.

Enceladus. Image credits: NASA/JPL.

On September 15, 2017, NASA de-commissioned the aging craft with a bang: they deorbited Cassini, letting it fall towards Saturn’s core and burn up in its atmosphere.

However, the wealth of information this tiny craft beamed back from its travels is still giving astronomers a lot to work on. Before its fiery demise, Cassini sampled the plume material ejected from the subsurface of Enceladus. Using its Cosmic Dust Analyzer (CDA) and the SwRI-led Ion and Neutral Mass Spectrometer (INMS) instruments, the craft analyzed both the plume itself and Saturn’s E-ring — which is formed by ice grains from the plumes trapped in Saturn’s gravity well.

Chemicals Enceladus.

Synthesis path of different aromatic cations identified in Enceladus’ plume.
Image credits F. Postberg et al., 2018, Nature.

During one of Cassini’s particularly close flybys of Enceladus (Oct. 28, 2015), the INMS detected molecular hydrogen in the moon’s plume ejections. Previous flybys also revealed the presence of a global subsurface ocean and a rocky core. This was the first indication that the moon can boast active geochemical below the surface, most likely between water and rocks in hydrothermal vents.

The presence of hydrogen was also grounds for great enthusiasm at NASA — the element is a known source of chemical energy for microbes living in hydrothermal vents here on good ol’ Earth.

“Once you have identified a potential food source for microbes, the next question to ask is ‘what is the nature of the complex organics in the ocean?'” says SwRI’s Dr. Hunter Waite, INMS principal investigator and paper coauthor. “This paper represents the first step in that understanding — complexity in the organic chemistry beyond our expectations!”

The findings are significant enough to influence further exploration, Glen believes. Any spacecraft that flies towards Enceladus in the future should make a point of going through its plume to analyze these complex organic molecules with a high-resolution mass spectrometer to “help us determine how they were made.”

“We must be cautious, but it is exciting to ponder that this finding indicates that the biological synthesis of organic molecules on Enceladus is possible.”

The paper “Macromolecular organic compounds from the depths of Enceladus” has been published in the journal Nature.

Cassini's last full-view picture of Saturn. Credit: NASA/JPL-Caltech/Space Science Institute.

Cassini’s stunning farewell picture of Saturn

On September 15, 2017, the daredevil Cassini spacecraft ended its 20-year voyage through space. It did so in style, plunging into Saturn’s atmosphere — the planet it had most closely studied in the past 13 years. Two days before spiraling into oblivion, the spacecraft fired the shutters of its wide-angle camera one last time. The result is this stunning full-body view of Saturn and its dazzling rings.

Cassini's last full-view picture of Saturn. Credit: NASA/JPL-Caltech/Space Science Institute.

Cassini’s last full-view picture of Saturn. Credit: NASA/JPL-Caltech/Space Science Institute.

A total of 80 wide-angle images were acquired over two hours. This mosaic view was pieced together from 42 of these shots, which were taken using red, green, and blue spectral filters, which when combined produce a natural-color picture.

“It was hard to say goodbye, but how lucky we were to be able to see it all through Cassini’s eyes!”

Though rather faint, you can spot six of Saturn’s 53 moons in the image — Enceladus, Epimetheus, Janus, Mimas, Pandora, and Prometheus.

“For 37 years, Voyager 1’s last view of Saturn has been, for me, one of the most evocative images ever taken in the exploration of the solar system,” said Carolyn Porco, Cassini imaging team leader.

“In a similar vein, this ‘Farewell to Saturn’ will forevermore serve as a reminder of the dramatic conclusion to that wondrous time humankind spent in intimate study of our sun’s most iconic planetary system,” she added.

Annotated version. Credit: NASA/JPL-Caltech/Space Science Institute.

Annotated version. Credit: NASA/JPL-Caltech/Space Science Institute.

When it took the shot, Cassini was approximately 698,000 miles (1.1 million kilometers) from Saturn, facing the gas giant’s sunlit side about 15 degrees above the ring plane.

NASA’s Cassini-Huygens mission launched in 1997 and took seven years to reach its destination around Saturn. Over the course of its long mission, Cassini’s achievements were legion. Besides landing a freaking probe on Titan, a methane-filled world similar to the early days of Earth before life evolved, Cassini made the most planetary flybys of any spacecraft — over 100. Before arriving in Saturn’s orbit, Cassini circled Earth, Venus, and Jupiter.

“It was all too easy to get used to receiving new images from the Saturn system on a daily basis, seeing new sights, watching things change,” said Elizabeth Turtle, an imaging team associate at the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland. “It was hard to say goodbye, but how lucky we were to be able to see it all through Cassini’s eyes!”

 

Saturn rings

Cassini is no more, but it left us one of the most memorable photos of Saturn

After twenty years in space, thirteen of which orbiting Saturn and its moons, the enduring Cassini spacecraft finally met its end on September 15, 2017. The trove of images and scientific data it beamed back, however, will keep scientists busy and the general public entertaining for many more years to come. For instance, NASA spoils us with this amazing shot of Saturn and its icy rings — one of the most spectacular we’ve seen so far.

Saturn rings

Credit: NASA/JPL-Caltech/Space Science Institute.

 

The photo was taken just a month before the spacecraft made a suicide plunge into Saturn’s atmosphere. At the time, Cassini was a staggering 600,000 km away from the planet, which, even so, still looks enormous.

Saturn has four main groups of rings and three fainter, narrower ring groups, separated by gaps called divisions. Each ring group is made up of thousands of smaller rings made of ice and debris, in some places no thicker than a few meters. In between Saturn’s cloud tops and the innermost D ring, the spacecraft passed through 22 times before it ended its mission. Before Cassini’s plunges were routed, scientists spent countless hours analyzing such images in search for debris that might prove hazardous to the spacecraft.

Remarkably, besides Saturn and some of its ring groups, the image also features an outlier: Saturn’s moon Pandora. Discovered in October 1980 by Voyager 1, the potato-shaped moon has 25.3 miles (40.7 km) mean radius. In this particular image, seen in the top-right corner, it barely measures more than a single pixel.

The image was taken in  with the spacecraft’s wide-angle camera. To increase visibility, Pandora was brightened by a factor of 2.

Cassini's best close-up view of Saturn's F ring shepherd moon, Pandora, taken in December 2016. Credit: NASA.

Cassini’s best close-up view of Saturn’s F ring shepherd moon, Pandora, taken in December 2016. Credit: NASA.

Over the course of its long mission, Cassini’s achievements were legion. Besides landing a probe on Titan, a methane-filled world similar to the early days of Earth before life evolved, Cassini made the most planetary flybys of any spacecraft — over 100. Before arriving in Saturn’s orbit, Cassini circled Earth, Venus, and Jupiter.

goodbye-cassini

Cassini’s farewell photo of Saturn’s dark side

goodbye-cassini

Credit: NASA/JPL-Caltech/Space Science Institute

Last month, the formidable Cassini spacecraft ended its 20-year-mission with a nose dive into Saturn’s atmosphere. NASA’s Cassini-Huygens mission launched in 1997 and took seven years to reach its destination around Saturn and its 53 moons. Over the course of its long mission, Cassini’s achievements were legion. Besides landing a freaking probe on Titan, a methane-filled world similar to the early days of Earth before life evolved, Cassini made the most planetary flybys any man-made craft ever has — over 100. Before arriving in Saturn’s orbit, Cassini circled Earth, Venus, and Jupiter.

It was over the course of these flybys that Cassini took some of the most breath-taking pictures of Saturn. Now, NASA has another one worthy of Cassini’s ‘best of’ collection — a unique view of Saturn’s dark side.

Because Earth orbits much closer to the sun than Saturn, ground-based telescopes were never able to observe the gas giant’s dark side. As such, this image would have never been possible were it not for the Cassini spacecraft.

The picture was taken on 7 June 2017, with the spacecraft’s onboard wide-angle camera. At the time, Cassini was about 1.21 million kilometers from Saturn, facing the sun-lit side of the rings seven degrees above the plane of rings.

Though the spacecraft itself is toast, the mission will live on for many years. During its 20-year trip, Cassini has beamed back a trove of data and images which will keep scientists busy for a long time. Perhaps, the mission’s most important contributions to science are still a work in progress.

cassini-spacecraft

Cassini spacecraft ends 20-year-old voyage in style, crashes into Saturn

Earlier this month, NASA’s Cassini probe embarked on a death spiral around Saturn’s orbit. Now, on Friday morning, September 15, scientists reported that they have received the last-ever message relayed by the probe, shortly before in plunged into the gas giant’s atmosphere.

cassini-spacecraft

Illustration of Cassini spacecraft prepping to dive into Saturn’s atmosphere. Credit: NASA.

This was the climax of a 20-year mission which was the $4-billion probe travel over two billion miles to Saturn. The collaborative mission between NASA, the European Space Agency and the Italian Space Agency aimed to study Saturn and its moons from close up and in the process learn more about the solar system and how it was formed.

Cassini-Huygens launched in 1997 and took seven years to reach its destination around Saturn and its 53 moonsThe Huygens probe detached from the Cassini spacecraft in 2005 when it landed on Titan, Saturn’s largest moon. “This was humanity’s first successful attempt to land a probe on another world in the outer solar system,” the ESA says.

Over the course of its long mission, Cassini’s achievements were legion. Besides landing a freaking probe on Titan, a methane-filled world similar to the early days of Earth before life evolved, Cassini made the most planetary flybys any man-made craft ever has — over 100. Before arriving in Saturn’s orbit, Cassini circled Earth, Venus, and Jupiter. It was during these flybys that the most detailed true color photos of the gas giant ever recorded were beamed back to Earth.

Amazing real-life photo of Jupiter captured by Cassini in 2000. Credit: NASA.

Amazing real-life photo of Jupiter captured by Cassini in 2000. Credit: NASA.

Like a true explorer, Cassini has found hidden ‘lands and treatures’. No fewer than seven moons orbiting Saturn were identified by the spacecraft.  These include Methone, Pallene, Polydeuces, Daphnis, Anthe and Aegaeon.

The most important findings, however, were those considering Saturn’s icy moon Enceladus. During the spacecraft’s frequent flybys of the icy moon thought to host a hidden ocean of liquid water beneath hundreds of miles of ice, scientists found hints of conditions favorable for microbial life. NASA claims Enceladus has “water, organic carbon, nitrogen [in the form of ammonia], and an energy source,” which no other environment besides Earth can boast.

“As we continue to learn more about Enceladus, and compare data from different instruments, we are finding more and more evidence for a habitable ocean world,” Linda Spilker, Cassini Project Scientist, told NASA. “If life is eventually discovered in Enceladus’ ocean by a mission after Cassini, then our Enceladus discoveries will have been among the top discoveries for all planetary missions.”

After two decades of interplanetary travel, however, Cassini finally ran out of fuel. It still had enough left to power its boosters for another few years but NASA mission engineers didn’t want to take the risk of an uncontrolled landing on Titan or Enceladus. Instead, NASA seized the opportunity to plunge the spacecraft into Saturn’s atmosphere. For one last time, Cassini spread its wings and used its instruments to sample Saturn’s atmosphere. This information will teach us new things about a totally alien environment. A few minutes later, Cassini vaporized bellowing a ‘scream’ that took 83 minutes to reach Earth. It was then that the mission control announced ‘the end of the mission’ in a burst of applause, commemorating one of the most successful space missions in history.

We’re not done yet

Despite 13 years in Saturn’s orbit, there are still many unanswered questions. It’s still not clear how long a Saturnian day lasts and the planet’s magnetic field seems to behave capriciously. And though Cassini made extremely exciting discoveries that signal potentially habitable conditions on Enceladus, we still need more data before we can come to any sensible conclusions.

“We’ve left the world informed, but still wondering,” Cassini-Huygens program manager Earl Maize told reporters at a press conference days before Cassini’s suicidal death plunge. “As a scientist, I couldn’t ask for more.”

After all this mission, there’s a single conclusion we can draw: we have to come back. One thing’s for sure, Cassini didn’t perish in vain.

Yup, that's Earth as seen by Cassini from 1.44 billion kilometres away. Is this worth your tax dollar? YES!

Yup, that’s Earth as seen by Cassini from 1.44 billion kilometres away. Is this worth your tax dollar? YES! Credit: NASA/JPL.

Cassini.

The Grand Finale: NASA plans to see Cassini off with a trail of fire as it crashes into Saturn

The Cassini spacecraft will get a burial place fit for such a long-trekked explorer: Saturn.

Cassini.

Artist’s redering of Cassini passing below Saturn’s innermost ring.
Image credits NASA/JPL-Caltech.

This small but venerable craft let humanity peer into Saturn and its moons on a level of detail our ancestors couldn’t even dream about. Throughout its explorations, Cassini beamed back breathtaking photographs, ignited hope for life on Jovian and Saturnian moons, and performed humanity’s most distant landing.

After a life of exploratory glory, Cassini is currently about halfway through the last leg of its journey. So NASA has decided to show the craft off with fire in the sky: on its last day before fuel runs out, 15 September, Cassini will dive into Saturn’s atmosphere to be vaporized in a blaze of glory. This is necessary to ensure that Cassin won’t infect any of the other nearby places (which could harbor indigenous life) with any clandestine Earth germs.

Still, the ship isn’t beat yet, and still, has important work to do as it gets closer to Saturn than any man-made object ever has. For instance, it has recently found that Saturn’s magnetic field doesn’t have any particular tilt, which is quite problematic since a) scientists were planning to use that to calculate how long a day is on Saturn and b) it kinda throws a wrench in our understanding of planets. It was thought that tilt is instrumental in generating a planet’s magnetic field, by allowing charges to form and flow through the liquid metal — but Saturn does without it.

“This planned conclusion for Cassini’s journey was far and away the preferred choice for the mission’s scientists,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “Cassini will make some of its most extraordinary observations at the end of its long life.”

“No spacecraft has ever gone through the unique region that we’ll attempt to boldly cross 22 times,” added Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. “What we learn from Cassini’s daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve.”

“This is truly discovery in action to the very end.”

Here’s a video from NASA detailing Cassini’s final mission. It’s quite epic.

EDIT: This article has been edited. The title and one paragraph erroneously stated that Cassini was headed for Jupiter, instead of Saturn.

Artist illustration of Cassini diving through Saturn's rings. Credit: NASA.

Cassini heard ‘the big empty’ when it dived through Saturn and its rings

Today, May 2nd, a spacecraft that has been orbiting Saturn since 2004 is preparing to embark on its grand finale: a series of trips that will see Cassini zip through the planet’s rings. A week earlier, however, the spacecraft dived through a previously unexplored area between Saturn and its innermost ring. As it dived, it listened for any signs of particles, like dust, that might hit its sensitive antenna. Cassini recorded the sound of ’emptiness’ and this was totally unexpected for everyone involved.

“The region between the rings and Saturn is ‘the big empty,’ apparently,” said Cassini Project Manager Earl Maize of NASA’s Jet Propulsion Laboratory, in a statement to the press. “Cassini will stay the course, while the scientists work on the mystery of why the dust level is much lower than expected.”

Artist illustration of Cassini diving through Saturn's rings. Credit: NASA.

Artist illustration of Cassini diving through Saturn’s rings. Credit: NASA.

The dive from April 26 did record ‘something’. The spacecraft is equipped with a highly sensitive device called the Radio and Plasma Wave Science instrument which picks up radio and plasma waves around Saturn. Dust that hits the antenna is also recorded although not directly acoustically like in the case of a microphone. Be them charged particles or chunks of dust, these signals are ultimately converted to an audio format, where the peaks in the signal correspond to pops and cracks. See how different it sounded when Casini passed through a faint, dusty ring on Dec. 18, 2016: Tom Yulsman wrote for Discover that the “pops and cracks toward the middle is the sound of a very dusty environment.”

“It was a bit disorienting — we weren’t hearing what we expected to hear,” William Kurth, RPWS team lead at the University of Iowa, said in a statement. “I’ve listened to our data from the first dive several times and I can probably count on my hands the number of dust particle impacts I hear.”

So, even though the gap between Saturn and its rings is just 1,200 miles (2,000 kilometers) wide and despite NASA images of ice and rock particles, this region is surprisingly empty.

After today’s dive, Cassini is scheduled to make no more than two dozen orbits around Saturn. Each time, it will dive through some of Saturn’s rings until ultimately crashing into the planet’s atmosphere during the grand finale on September 15.

NASA’s Cassini spacecraft to finally reach Saturn’s rings

The Cassini spacecraft, which has already had a helluva ride, is preparing for an exciting stage: studying Saturn’s rings.

Saturn’s rings were named alphabetically in the order they were discovered. The narrow F ring marks the outer boundary of the main ring system.
Credits: NASA/JPL-Caltech/Space Science Institute

After more than 19 years, 300,000 mind-blowing images and the discovery of seven moons, Cassini is starting its swansong. After orbiting Saturn since 2004 and making numerous dramatic discoveries including a global ocean within Enceladus and liquid methane seas on Titan, Cassini is preparing for its final maneuvers.

“We’re calling this phase of the mission Cassini’s Ring-Grazing Orbits, because we’ll be skimming past the outer edge of the rings,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California. “In addition, we have two instruments that can sample particles and gases as we cross the ringplane, so in a sense Cassini is also ‘grazing’ on the rings.”

By April 2017, Cassini is expected to dive through the unexplored region at the outer edge of the main rings 20 times, a region where no other spacecraft has even attempted to go. During these flybys, Cassini will also gather sample ring particles and molecules of faint gases that are found close to the rings. This is the closest we’ve ever gotten to Saturn and its rings.

The thing is, Cassini was never really designed for this but its mission was so successful that NASA just aimed higher and higher. We at ZME Science have written no less than 271 articles on Cassini’s work, and by now it’s without a doubt one of the most exciting scientific missions ever undertaken. But even so, Cassini is not safe.

“I am a little unsettled by what we are going to try and do as far as the science is concerned because neither the instrument nor the spacecraft were designed to do this,” said Michele Dougherty,” professor of space physics at Imperial College London and lead for Cassini’s Magnetometer. But for the moment, she is confident and looking forward to the task.

“We are going to try and understand what is going on in the interior of Saturn and we are going to try and work out how long a day on Saturn is – it is a bit embarrassing, but we still don’t know, “said Dougherty. “You use the magnetic field, which is what my instrument measures, to almost see inside the planet.”

If that goes fine, then Cassini, which is running quite low on fuel, will enter its final stage. After April 2017, it will start making maneuvers to dive towards Saturn, preparing its mission-ending plunge into the planet’s atmosphere on Sept. 15. The design and success of the spacecraft remains an inspiration for future missions

Computer models confirm icy eruptions on Saturn’s Moon

A few years ago, the Cassini spacecraft made a surprising discovery: there are geysers erupting on Saturn’s moon Enceladus, spewing water and ice to great heights. However, the process which causes these geysers remained unknown or controversial. Now, scientists at the University of Chicago and Princeton University have pinpointed a mechanism through which Saturn’s tidal forces exert constant stress and cause long-term icy eruptions.

Ice and volcanoes

This enhanced color view of Enceladus shows much of the southern hemisphere and includes the south polar terrain at the bottom of the image. Scientists at the University of Chicago and Princeton University have published a new study describing the process that drives and sustains this moon of Saturn's long-lived geysers. Photo by NASA/JPL

This enhanced color view of Enceladus shows much of the southern hemisphere and includes the south polar terrain at the bottom of the image. Scientists at the University of Chicago and Princeton University have published a new study describing the process that drives and sustains this moon of Saturn’s long-lived geysers. Photo by NASA/JPL

Enceladus is is the sixth-largest moon of Saturn, measuring only 500 kilometers (310 mi) in diameter. Enceladus is covered by fresh, clean ice, reflecting almost all the sunlight that strikes it. However, Enceladus displays a surprisingly large variety of geological features, including rifts, canyons, grooves, ridges and fractures, likely caused by the stress exerted on the moon by its parent planet, Saturn. This stress also causes massive friction inside the planet, which led researchers to believe that there might be a liquid ocean under Enceladus’ frozen surface — and potentially, life. Disregarded once as frozen and barren wasteland, the moon is now one of the likeliest places to find extraterrestrial life.

But one big question still remained: why are these eruptions happening in the first place?

“On Earth, eruptions don’t tend to continue for long,” said Edwin Kite, assistant professor of geophysical sciences at UChicago, who led this study. “When you do see eruptions that continue for a long time, they’ll be localized into a few pipelike eruptions with wide spacing between them.”

Enceladus has multiple fissures along its south pole. These “tiger stripes” have been erupting for decades, and it’s strange that the geysers haven’t clogged up on themselves. Somehow, these icy eruptions kept going and going.

“It’s a puzzle to explain why the fissure system doesn’t clog up with its own frost,” Kite said. “And it’s a puzzle to explain why the energy removed from the water table by evaporative cooling doesn’t just ice things over.”

Kite suspected there was another source of energy, responsible for cleaning the site. Now, after creating several models of the site, they believe they’ve zoomed in on this factor:

“We think the energy source is a new mechanism of tidal dissipation that had not been previously considered,” Kite said. Kite and Princeton’s Allan Rubin present their findings the week of March 28 in the Early edition of the Proceedings of the National Academy of Sciences.

Life beneath a frozen moon

: Possible Hydrothermal Activity (Artist’s Concept)
This cutaway view of Saturn’s moon Enceladus is an artist’s rendering that depicts possible hydrothermal activity that may be taking place on and under the seafloor of the moon’s subsurface ocean, based on recently published results from NASA’s Cassini mission. Credits: NASA/JPL

Understanding this system is extremely important for astrobiological studies (the search for extraterrestrial life). As I mentioned above, Enceladus is one of the top candidates for extraterrestrial life. Kite even calls it “an opportunity for the best astrobiology experiment in the solar system,” and for good reason. Not only is it extremely likely that it hosts an ocean of liquid water, but Cassini’s data indicates that the icy volcanoes probably originate in a biomolecule-friendly oceanic environment.

The erupted plumes have been shown to have grains of silica-rich sand, nitrogen (in ammonia), nutrients and organic molecules, including trace amounts of simple hydrocarbons such as methane. All these are indicators of hydrothermal activity in Enceladus’ ocean; hydrothermal vents are generally regarded as ideal places for life to thrive. To make things even better, models indicates the large rocky core is porous, allowing water to flow through it to pick up heat.

Europa, one of Jupiter’s moons is in a very similar situation, and the team now wants to apply similar models for it.

“Europa’s surface has many similarities to Enceladus’s surface, and so I hope that this model will be useful for Europa as well,” Kite said.

Robotic exploration missions have been planned for both moons, but no clear timeline has been drawn.

NASA prepares for historic Cassini flyby

NASA is preparing for a historical approach to Enceladus, plunging its Cassini spacecraft deep through the icy spray coming from the ocean on Enceladus.

An Ocean and Geysers on Enceladus

A Cassini mosaic of degraded craters, fractures, and disrupted terrain in Enceladus’s north polar region. Image via Wikipedia.

After years and years of observations, deductions and scientific reasoning, NASA can now say with almost certainty that there is an ocean of liquid water on Enceladus, hidden beneath its frozen surface – which makes it a very interesting target for detecting alien life.

Enceladus is the sixth-largest moon of Saturn, measuring only 500 km in diameter. It’s covered in fresh, clean ice that reflects most of the sun waves that reach it, but it has long been believed that Saturn’s tidal forces cause a shear stress on Enceladus, which in turn causes friction and generates enough heat for water to remain liquid beneath the surface. In 2005, the Cassini spacecraft started multiple close flybys of Enceladus, revealing its surface and environment in greater detail. Among its most interesting findings, Cassini reported a water-rich plume venting from the south polar region of Enceladus; by now, over 100 geysers have been identified, spewing not only liquid water, but also volatiles and even solid material, such as salt (sodium chloride). This seems to indicate that Enceladus not only has a liquid ocean of water, but also hydrothermal activity – which also rises the chances of emerging life.

These geyser observations, along with the finding of escaping internal heat and very few (if any) impact craters in the south polar region, show that Enceladus is geologically active today; you can see tectonic features on its surface, most notably the above described “water volcanism“. There are also relatively crater-free regions filled with numerous small ridges and scarps, as well as fissures, plains, corrugated terrain and other crustal deformations.

This artist’s rendering showing a cutaway view into the interior of Saturn’s moon Enceladus. Image via NASA.

Flying by

It’s not the first time Cassini flew by Enceladus, but it’s the first time it will be plunging deep through a fountain of this water/ice spray.

“This daring flyby will bring the spacecraft within 30 miles (48 kilometers) of the surface of Enceladus’s south polar region,” NASA said in a statement.  “The encounter will allow Cassini to obtain the most accurate measurements yet of the plume’s composition, and new insights into the ocean world beneath the ice.”

The mission’s purpose is not to directly detect life, but rather to provide powerful new insights about how habitable the ocean environment is within Enceladus. Specifically, Cassini’s flyby will offer chemical and physical information about the hydrothermal activity, both about the water and the rock around it. The low altitude of the encounter is, in part, intended to afford Cassini greater sensitivity to heavier, more massive molecules, including organics. We will also find out whether the icy spurts are column-like, individual jets, or sinuous, icy curtain eruptions (or some combination of both, or something completely different). Researchers also want to see just how much material is ejected.

All in all, Cassini can’t figure out on its own if there is life on Enceladus – it wasn’t built for that. But it can do the next best thing – see if the conditions are suitable for life. Enceladus looks like one of the hottest places to find life in the solar system.

Image credits: NASA/JPL

New ‘Mystery Islands’ found on Titan’s Methane Sea

The enduring Cassini spacecraft returns with new insight into the hydrocarbon seas from Saturn’s moon Titan. The latest findings were reported after the spacecraft’s most recent flyby above Titan’s northern hemisphere on August 21, where it performed observations of the largest liquid methane/ethane sea, the 400,000 square kilometre Kraken Mare. The Cassini astronomers were looking to probe the methane sea’s depths, but meanwhile they come across something more interesting: strange floating features reminiscent of the “Magic Island” found on Ligeia Mare, another large methane sea.

Bright features on a huge sea of liquid methane

In contrast to a previously reported bright, mystery feature called “Magic Island” in another of Titan’s large seas, Ligeia Mare, these new features were observed with both  radar data and images from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS). Because the researchers have two different data sets at two different wavelengths this will help them better assess what these mysterious features represent. So far, the VIMS data suggests these features might be waves or floating debris.

Mystery island

Cassini’s radar instrument images show that a bright feature appeared in Kraken Mare, Titan’s largest sea.
Image Credit: NASA/JPL-Caltech/ASI/Cornell

Ligeia Mare’s Magic Island was first discovered in July 2013,  covering an area of some 260 square kilometres. During another flyby in August 2013, data from the Synthetic Aperture Radar (SAR) showed that Magic Island was still there yet the bright features had evolved. Clearly, Cassini shows that Titan’s polar seas are extremely dynamic and hold many mysteries. More observations are required, but our next shot won’t be until January 2015, when Cassini is scheduled to observe the original “magic island” feature in Ligeia Mare once more.

On another note, just last week the same Cassini team put a huge grin up all our faces when they release some stunning photos of light bouncing off Titan’s atmosphere. Here are two of the best shots:

Image credits: NASA/JPL

Image credits: NASA/JPL

Another image from Cassini’s Visual and Infrared Mapping Spectrometer on July 24, 2012, showing a sunlight reflection on a Titanian sea. Image credits: Barnes et al./NASA/JPL/University of Arizona

Another image from Cassini’s Visual and Infrared Mapping Spectrometer on July 24, 2012, showing a sunlight reflection on a Titanian sea. Image credits: Barnes et al./NASA/JPL/University of Arizona

A shallow extraterrestrial sea

During this most recent flyby, Cassini also probed the depths of Kraken Mare. The spacecraft collect altimetry (or height) data, using the spacecraft’s radar instrument along a 120-mile (200-kilometer) shore-to-shore track of Kraken Mare. Reflections were isolated for a shallow 40 km segment. The distinctive double-peaked returns from a region near the mouth of a flooded river valley that feeds the sea indicates liquid methane depths of 20-35 m. For the remainder of 160 km, no observations could be made. The signal most likely became skewed because the liquid was more absorbing than Ligeia Mare or the depths were too high (greater than 200m). For comparison, central Ligeia Mare was 160 m deep. It should be interesting to see how deep Kraken Mare is off-coast.

Cassini radar data reveal the depth of a liquid methane/ethane sea on Saturn's moon Titan near the mouth of a large, flooded river valley. Image Credit: NASA/JPL-Caltech/ASI/Cornell

Cassini radar data reveal the depth of a liquid methane/ethane sea on Saturn’s moon Titan near the mouth of a large, flooded river valley.
Image Credit: NASA/JPL-Caltech/ASI/Cornell

Learn more at NASA’s Cassini mission homepage.

 

 

 

Cassini captures stunning picture of Titan’s seas

Saturn’s Moon Titan is a remarkable place; it’s the only place aside for the Earth which has liquids on its surface – albeit, the liquid isn’t water, but rather hydrocarbons: methane and ethane. Titan is too cold to have liquid water on its surface, but that doesn’t make it any less spectacular. NASA’s Cassini spacecraft captured some amazing pictures of the sunlight bouncing off of them, as you can see below.

Image credits: NASA/JPL

“In the past, Cassini had captured, separately, views of the polar seas and the sun glinting off them, but this is the first time both have been seen together in the same view”, NASA said on their website.

Indeed, the achievements of the Cassini probe are fantastic. From Saturn’s orbit, it took pictures of Venus, the Earth, and of course, Saturn and Titan. It even managed to capture some hydrocarbon rivers flowing on the satellite’s surface. These images were taken in infrared, to allow researchers to better see the surface through the hydrocarbon haze which perpetually shrouds the moon.

The atmosphere of Titan is known as the only fully developed atmosphere that exists on a natural satellite in the Solar System. Ever since the early 20th century it was believed that Titan has not only an atmosphere, but also liquids on its surfaces. Observations from the Voyager space probes have shown that the Titanean atmosphere is denser than Earth’s, hazing the satellite, and the Cassini probe showed that Titan has a complex weather system, with hydrocarbon rains, rivers and oceans.

Another image from Cassini’s Visual and Infrared Mapping Spectrometer on July 24, 2012, showing a sunlight reflection on a Titanian sea. Image credits: Barnes et al./NASA/JPL/University of Arizona

 

As you can see, an arrow-shaped complex of bright methane clouds hovers near Titan’s north pole. These clouds are causing almost continuous rainfall, constantly refilling the lakes. However, evaporation is the dominant phenomenon at this time. You can observe a “bathtub ring,” or bright margin, around Kraken Mare (the sea containing the reflected sunglint). This means that it was bigger at some point, but through evaporation, it has lost some of its liquids. This bears a striking similarity to Earth’s own hydrological system, where some seas become smaller while others grow. Along the years, Cassini has often time showed photos which supported this similarity, most notably rivers flowing into lakes and oceans.

However, there are also many huge differences. Titan is much colder than the coldest places on our planet, hence we have liquid methane instead of water. Also, there appear to be no currents in the water bodies, only shallow waves; for the most part, they seem to be almost perfectly flat.

Radar image of some of the many seas and lakes near Titan’s north pole. Image Credit: NASA/JPL

It’s still not clear if Titan hosts any type of life forms. In June 2010, scientists analysing data from the Cassini–Huygens mission reported anomalies in the atmosphere near the surface which could be consistent with the presence of methane-producing organisms, but may alternatively be due to non-living chemical or meteorological processes. The fact that it doesn’t have any liquid water on the surface indicates that we shouldn’t expect to find water-based life forms, but there have been consistent indications of liquid water under the layer of ice. The proposed Titan Mare Explorer mission, a low-cost lander which would splash down in a lake, “would have the possibility of detecting life”, according to cosmologist Chris Impey of the University of Arizona. The proposed start date for that mission is 2016.

The Cassini probe has been taking pictures ever since 2004 and is planned to last until at least 2017, promising more discoveries. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA’s Science Mission Directorate in Washington. You can find out more information about Cassini here:

http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov

Ingredient of Household Plastic Found on Saturn Moon

NASA’s Cassini spacecraft has detected propylene, a chemical used greatly in everyday life, in things like food-storage containers, car bumpers and other consumer products, on Saturn’s Moon Titan. I really recommend watching the video below, as it explains the situation in great detail:

A small amount of propylene was identified in Titan’s lower atmosphere by Cassini’s Composite Infrared Spectrometer (CIRS); the device measures infrared emissions given away by Saturn and Saturn’s moons in a similar way to the way our hands feel a fire’s warmth. Every gas has a unique thermal fingerprint, and based on that, CIRS can identify pretty much every gas. The only problem is isolating the signal from other, interfering signals.

“This measurement was very difficult to make because propylene’s weak signature is crowded by related chemicals with much stronger signals,” said Michael Flasar, Goddard scientist and principal investigator for CIRS. “This success boosts our confidence that we will find still more chemicals long hidden in Titan’s atmosphere.”

This detection brings a valuable piece of the puzzle, a piece which was sought after since the Voyager 1 spacecraft and the first-ever close flyby of this moon in 1980. Voyager identified many of the gases in Titan’s hazy brownish atmosphere as hydrocarbons, a class of organic chemical compounds composed only of the elements carbon (C) and hydrogen (H) which compose most of the petroleum and natural gas.

False-color images, made from data obtained by NASA's Cassini spacecraft, shows clouds covering parts of Saturn's moon Titan in yellow.

False-color images, made from data obtained by NASA’s Cassini spacecraft, shows clouds covering parts of Saturn’s moon Titan in yellow.

In Titan’s atmosphere, hydrocarbons form after sunlight breaks apart methane, the second-most plentiful gas in that atmosphere. The new fragments can bond together, forming chains of 2, 3, or even more carbons – ethane and propane for example, can be created this way.

As Cassini continued to discover more and more hydrocarbons on Titan, propylene remained elusive until the CIRS analysis.

“I am always excited when scientists discover a molecule that has never been observed before in an atmosphere,” said Scott Edgington, Cassini’s deputy project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “This new piece of the puzzle will provide an additional test of how well we understand the chemical zoo that makes up Titan’s atmosphere.”

For more information on the Cassini mission, visit NASA’s page.

Via NASA.

Water churned up from Saturn’s depths by massive storm

If you were to look at them from the safety and serenity of your home, the gas giants of our solar system seem to be quite peaceful. Their surface appears smooth, unscathed by meteor impacts or other such phenomena – but this couldn’t be further from the truth, as they sometimes show us.

saturn

In 2010, Saturn began stirring things up, with a giant storm; the storm quickly grew to amazing proportions, reaching 15,000 kilometers (more than 9,300 miles) in width and visible to amateur astronomers on Earth as a great white spot dancing across the surface of the planet.

Now, thanks to near-infrared spectral measurements taken by NASA’s evergreen Cassini orbiter and analysis conducted by the University of Wisconsin-Madison, Saturn’s superstorm is helping researchers understand more about the planet’s deep atmosphere – at heighs typically obscured by a thick haze.

The size of this storm is just mind blowing: 15.000 km wide, 300 km long, covering an entire surface of 4,500,000,000 square km. Just so you can get a term of comparison, the size of the Earth is 510,000,000 square km – almost 1.000 times less!

Astronomers found that loud particles at the top of the great storm are composed of a mix of three substances: water ice, ammonia ice, and… something else, which is yet to be identified – possibly ammonium hydrosulfide. The phenomena which brought these substances forth is also significant.

“We think this huge thunderstorm is driving these cloud particles upward, sort of like a volcano bringing up material from the depths and making it visible from outside the atmosphere,” explains Sromovsky, a senior scientist at UW-Madison and an expert on planetary atmospheres. “The upper haze is so optically pretty thick that it is only in the stormy regions where the haze is penetrated by powerful updrafts that you can see evidence for the ammonia ice and the water ice. Those storm particles have an infrared color signature that is very different from the haze particles in the surrounding atmosphere.”

The new work also helps to validate current models of Saturn storms, giving us a better understanding of gas giant atmospheric processes.

“The water could only have risen from below, driven upward by powerful convection originating deep in the atmosphere. The water vapor condenses and freezes as it rises. It then likely becomes coated with more volatile materials like ammonium hydrosulfide and ammonia as the temperature decreases with their ascent,” Sromovsky adds.

Journal Reference:
L.A. Sromovsky, K.H. Baines, P.M. Fry. Saturn’s Great Storm of 2010–2011: Evidence for ammonia and water ices from analysis of VIMS spectra. Icarus, 2013; 226 (1): 402 DOI: 10.1016/j.icarus.2013.05.043

Iapetus – the black-and-white walnut Moon

Iapetus is the third largest moon of Saturn, with a radius of about 42% that of our moon, and a mass that weighs up to only 2.5%. But Iapetus has a number of shocking features, unique throughout the entire solar system.

The Walnut Moon

walnut moon

This is the equatorial ridge that  runs along the center of Cassini Regio; in case you were wondering, the ridge has an average height of 13 km, occasionally going up to 20km, a length of 1,300 km and a width of about 20 km. It was discovered when the Cassini spacecraft imaged Iapetus on December 31, 2004, and even in 2013, it has astronomers baffled. Why did it form and why does it follow the equator so closely, no one knows for sure, though there are three competing theories:

1. The ridge could be a remnant of the oblate shape of the young Iapetus, when it was rotating more rapidly than it does today, but if this were to be true, for reasons you can read here, this would mean that the moon was formed much earlier than previously believed.

2. The ridge could be icy material that welled up from beneath the surface and then solidified – this hypothesis requires that rotational axis would have been driven to its current position by the ridge.

3. Iapetus could have had a ring system during its formation and the ridge is actually an accretion of that material. However, the ridge appears too solid to be the result of a collapsed ring, and images show tectonic faults crossing the ridge, so this seems highly unlikely.

The likelihood of any theory is not striking, and the matter is still a hot topic among some astronomic circles.

Black and white

iapetus bright

In the 17th century, Giovanni Cassini observed that he could see Iapetus only on the west side of Saturn and he could never see it on the east. So Cassini, the bright man that he was, deducted that Iapetus is locked in synchronous rotation about Saturn (much like the Moon is to the Earth) and that one side is darker than the other. Centuries passed until actual images confirmed this man’s deduction, but Cassini wasn’t able to explain why this is.

The difference is striking – the leading hemisphere and sides are dark while most of the trailing hemisphere and poles are bright. To make it even more puzzling, when the Cassini spacecraft passed at only 1640 km from Iapetus, it showed that both hemispheres are heavily cratered.

Now, NASA researchers believe the dark material is a lag (residue) from the sublimation (evaporatio

iapetus darkn) of water ice on the surface of Iapetus, possibly darkened by exposure to sunlight. Another possibility is that the front hemisphere is gathering brighter matter, much like your windshield gathers most of the dust, leaving the back of the car cleaner.

 

Iapetus has been imaged multiple times from moderate distances by the Cassini orbiter, but due to its distance to Saturn, close observation remains difficult; no near future flybys are planned, but a viewing opportunity will be possible 2 years from now.

Saturnian storm caught choking on its own tail

The Uroburos is a mythological symbol representing a serpent or dragon eating its own tail – a symbol of cyclicality and eternal return. The Cassini spacecraft watching Saturn recently caught a glimpse of a storm that looks remarkably like the mythological creature – only it choked on its own tail.

saturn

This mosaic of false-color images from NASA’s Cassini spacecraft shows what a giant storm in Saturn’s northern hemisphere looked like about a month after it began. The bright head of the storm is on the left. Via NASA.

The storm came out incredibly violent, churned around the planet until it made it to the other side and back again, choking on its own tail.

“This Saturn storm behaved like a terrestrial hurricane – but with a twist unique to Saturn,” said Andrew Ingersoll, a Cassini imaging team member based at the California Institute of Technology, Pasadena, who is a co-author on the new paper in the journal Icarus. “Even the giant storms at Jupiter don’t consume themselves like this, which goes to show that nature can play many awe-inspiring variations on a theme and surprise us again and again.”

Earth’s hurricanes typically feed off energy from warmer waters, leaving behind a cold-water wake – this storm in Saturn’s northern hemisphere also feasted off warm “air” in the gas giant’s atmosphere in a similar fashion. From what we know of however, terrestrial storms have never encountered their own wakes – they stumble upon topographic features such as mountains and are blocked by them. The bright, turbulent storm head was able to stomp a path all the way across the planet, and it was only when it ran into itself again that it stopped.

saturn2

This is also a mosaic of false color.

“This thunder-and-lightning storm on Saturn was a beast,” said Kunio Sayanagi, the paper’s lead author and a Cassini imaging team associate at Hampton University in Virginia. “The storm maintained its intensity for an unusually long time. The storm head itself thrashed for 201 days, and its updraft erupted with an intensity that would have sucked out the entire volume of Earth’s atmosphere in 150 days. And it also created the largest vortex ever observed in the troposphere of Saturn, expanding up to 7,500 miles [12,000 kilometers] across.”

Every Saturn year (~30 Earth years), massive storms occur – but this one was definitely the largest in that period.

“Cassini’s stay in the Saturn system has enabled us to marvel at the power of this storm,” said Scott Edgington, Cassini‘s deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We had front-row seats to a wonderful adventure movie and got to watch the whole plot from start to finish. These kinds of data help scientists compare weather patterns around our solar system and learn what sustains and extinguishes them.”

Via NASA