Tag Archives: Saturn

Storms on Saturn baffle scientists

The uncertainty of science: Scientists have identified a new type of storm on Saturn, and they don’t understand the weather processes that produced it.

Until now, astronomers had seen only two kinds of Saturnian storms: relatively small storms about 2,000 kilometers across that appear as bright clouds for a few days and Great White Spots that are 10 times as large and last for months. The newly spotted weather disturbance was a series of four midsize storms. Each was several thousand kilometers across and lasted between about 1.5 weeks and about seven months.

It appears that these midsize storms don’t fit any of their present theories about the formation of storms on Saturn.

However, for any scientist at this time to suggest that any theory about the storms on gas giants like Jupiter or Saturn can explain things is for that scientist to reveal themselves to be arrogant fools. We simply do not know anything about the deep atmospheres and vast climates of such planets. For example, we have yet to send a satellite to either planet devoted entirely to studying their atmospheres. And considering the size of these planets, such research would require a lot more than one orbiter to get a global picture. And it would require decades of coverage to get a long term picture.

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Astronomers find 20 more moons orbiting Saturn

Astronomers have discovered an additional twenty moons orbiting Saturn, bringing the total known to 82, three more than the 79 moons known to circle Jupiter.

Each of the newly discovered moons is about five kilometers, or three miles, in diameter. Seventeen of them orbit the planet backwards, or in a retrograde direction, meaning their movement is opposite of the planet’s rotation around its axis. The other three moons orbit in the prograde—the same direction as Saturn rotates.

Two of the prograde moons are closer to the planet and take about two years to travel once around Saturn. The more-distant retrograde moons and one of the prograde moons each take more than three years to complete an orbit.

The astronomers have also created a contest allowing the public to help name these new moons.

I will make one prediction: They are going to find many more.

In fact, Saturn’s rings and its numerous moons raise the question of what defines a moon. At present, a moon is defined as any object orbiting a planet, regardless of size. With Saturn’s rings however we have millions of objects orbiting that planet, many very tiny. It seems we have never put a size limit on the definition of a moon, and really need to.

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More organics detected in Enceladus’ plumes

Using Cassini archived data scientists have detected evidence of new organic molecules in the water-ice plumes coming from the tiger stripe fissures on Saturn’s moon Enceladus.

Powerful hydrothermal vents eject material from Enceladus’ core, which mixes with water from the moon’s massive subsurface ocean before it is released into space as water vapor and ice grains. The newly discovered molecules, condensed onto the ice grains, were determined to be nitrogen- and oxygen-bearing compounds.

On Earth, similar compounds are part of chemical reactions that produce amino acids, the building blocks of life. Hydrothermal vents on the ocean floor provide the energy that fuels the reactions. Scientists believe Enceladus’ hydrothermal vents may operate in the same way, supplying energy that leads to the production of amino acids.

For clarity I should point out that I am using the term “organics” as chemists do. It refers not to life, but to any molecule that is formed using carbon.

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The never-ending snowstorm circling Saturn

New data suggests that the water being spewed out of Enceladus’s tiger stripes is depositing so much snow and ice on Saturn’s three inner moons, Mimas, Enceladus and Tethys, that these moons, as well as Enceladus, are about twice as bright in radar than previously thought.

Dr Le Gall and a team of researchers from France and the US have analysed 60 radar observations of Saturn’s inner moons, drawing from the full database of observations taken by the Cassini mission between 2004 and 2017. They found that previous reporting on these observations had underestimated the radar brightness by a factor of two.

Unprotected by any atmospheres, Saturn’s inner moons are bombarded by grains of various origins which alter their surface composition and texture. Cassini radar observations can help assess these effects by giving insights into the purity of the satellites’ water ice.

The extreme radar brightness is most likely related to the geysers that pump water from Enceladus’s internal ocean into the region in which the three moons orbit. Ultra-clean water ice particles fall back onto Enceladus itself and precipitate as snow on the other moons’ surfaces.

Dr Le Gall, of LATMOS-UVSQ, Paris, explained: “The super-bright radar signals that we observe require a snow cover that is at least a few tens of centimetres thick. However, the composition alone cannot explain the extremely bright levels recorded. Radar waves can penetrate transparent ice down to few meters and therefore have more opportunities to bounce off buried structures. The sub-surfaces of Saturn’s inner moons must contain highly efficient retro-reflectors that preferentially backscatter radar waves towards their source.”

While the new results suggest that the surfaces of these moons are much brighter that expected, I find the circumstances they describe far more fascinating: a never-ending snow storm in the orbits around Saturn and landing continually on these moons.

My, isn’t the universe wonderful?

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New Hubble image of Saturn

Saturn taken by Hubble in 2019
Click for full image.

Astronomers have used the Hubble Space Telescope to snap a new high resolution image of Saturn. That image, cropped and reduced to post here, can be seen on the right.

The image was part of a new Hubble program to obtain regular images of the outer planets, begun in 2018.

[The Saturn images] reveal a planet with a turbulent, dynamic atmosphere. This year’s Hubble offering, for example, shows that a large storm visible in the 2018 Hubble image in the north polar region has vanished. Smaller storms pop into view like popcorn kernels popping in a microwave oven before disappearing just as quickly. Even the planet’s banded structure reveals subtle changes in color.

But the latest image shows plenty that hasn’t changed. The mysterious six-sided pattern, called the “hexagon,” still exists on the north pole. Caused by a high-speed jet stream, the hexagon was first discovered in 1981 by NASA’s Voyager 1 spacecraft.

As beautiful as this Hubble photograph is, I cannot help but be saddened by it. It is now the best image of Saturn we will get until 2036 at the earliest, when a NASA mission to Titan finally arrives.

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Exploding nitrogen on Titan

A new theory proposes that some of the smaller high rimmed methane lakes on Titan were formed when underground nitrogen warmed and exploded, forming the basin in which the methane ponded.

Most existing models that lay out the origin of Titan’s lakes show liquid methane dissolving the moon’s bedrock of ice and solid organic compounds, carving reservoirs that fill with the liquid. This may be the origin of a type of lake on Titan that has sharp boundaries. On Earth, bodies of water that formed similarly, by dissolving surrounding limestone, are known as karstic lakes.

The new, alternative models for some of the smaller lakes (tens of miles across) turns that theory upside down: It proposes pockets of liquid nitrogen in Titan’s crust warmed, turning into explosive gas that blew out craters, which then filled with liquid methane. The new theory explains why some of the smaller lakes near Titan’s north pole, like Winnipeg Lacus, appear in radar imaging to have very steep rims that tower above sea level – rims difficult to explain with the karstic model.

This is a theory that has merit. It also must be treated with skepticism, as our knowledge of Titan remains at this time very superficial, even with the more detailed information garnered from Cassini.

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A journey to Saturn’s moon Dione

Global Map of Dione

Cool image time! Today, for a change, I decided to spend some time rummaging through the Cassini raw image archive, mainly because I wanted to see some variety. At this time sadly almost all the good images coming from space are limited to Mars images, and I wished to post a cool image from somewhere else in the solar system.

The global map above was compiled from photographs of the Saturn moon Dione taken by Cassini during its thirteen years in orbit around the ringed giant.

The orange box indicates the sector of interest. The white outline indicates the location of the next photograph below and to the right, taken by Cassini during its first close fly-by of the moon on October 11, 2005, when the spacecraft was approaching the moon.
» Read more

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Weird minerals discovered in simulated Titan environment

In recreating their best guess as to the conditions and environment of Saturn’s moon Titan, scientists have produced a number of weird never-before-seen minerals.

To create Titan-like conditions in the laboratory, the researchers started with a custom-built cryostat, an apparatus to keep things cold. They filled the cryostat with liquid nitrogen to bring the temperature down. They then warmed the chamber slightly, so the nitrogen turned to gas, which is mostly what Titan’s atmosphere contains. Next, they threw in what abounds on Titan, methane and ethane, as well as other carbon-containing molecules, and looked for what formed.

The first things to drop out of their Titan hydrocarbon soup were benzene crystals. Benzene is perhaps best known as a component of gasoline and is a snowflake-shaped molecule made out of a hexagonal ring of carbon atoms. But Titan benzene held a surprise: The molecules rearranged themselves and allowed ethane molecules inside, creating a co-crystal.

The researchers then discovered the acetylene and butane co-crystal, which is probably a lot more common on Titan than benzene crystals, based on what’s known about the moon’s composition, Cable said.

The scientists think that these crystals might be found on the edge of Titan’s methane lakes, encrusted there like a bathtub ring.

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Data from Cassini’s last fly-by of Titan

Based on data from Cassini’s last fly-by of Titan, scientists have been able to estimate the depth of some of that planet’s northern lakes while also finding that they were filled mostly with methane.

The depths measured were as much as 300 feet. The data also shows that the geology of one hemisphere in the north was different from the other hemisphere.

On the eastern side of Titan, there are big seas with low elevation, canyons and islands. On the western side: small lakes. And the new measurements show the lakes perched atop big hills and plateaus. The new radar measurements confirm earlier findings that the lakes are far above sea level, but they conjure a new image of landforms – like mesas or buttes – sticking hundreds of feet above the surrounding landscape, with deep liquid lakes on top.

The fact that these western lakes are small – just tens of miles across – but very deep also tells scientists something new about their geology: It’s the best evidence yet that they likely formed when the surrounding bedrock of ice and solid organics chemically dissolved and collapsed. On Earth, similar water lakes are known as karstic lakes. Occurring in in areas like Germany, Croatia and the United States, they form when water dissolves limestone bedrock.

This data also suggests, as has previous data, that Titan could very well have extensive underground cave systems. Unlike the Moon or Mars, however, these are not going to be very hospitable to colonization, considering the presence of methane and the cold temperatures.

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Saturn’s rings desposit material on its tiny nearest moons

Pan

A new analysis of data from Cassini has confirmed that the tiny moons orbiting close to Saturn’s rings are repeatedly coated by material from those rings.

The new research, from data gathered by six of Cassini’s instruments before its mission ended in 2017, is a clear confirmation that dust and ice from the rings accretes onto the moons embedded within and near the rings.

Scientists also found the moon surfaces to be highly porous, further confirming that they were formed in multiple stages as ring material settled onto denser cores that might be remnants of a larger object that broke apart. The porosity also helps explain their shape: Rather than being spherical, they are blobby and ravioli-like, with material stuck around their equators. “We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators,” Buratti said. “A denser body would be more ball-shaped because gravity would pull the material in.”

This result is not a surprise. It has been hypothesized since the first images of these weirdly shaped moons (as illustrated by the picture of Pan from March 2017 above) were first beamed back by Cassini. This new analysis just helps confirm it.

I will add that searching through Behind the Black for that image of Pan made me realize how much I miss Cassini. I used to post lots of its images, always spectacular and breath-taking. With it gone, the images from Saturn have stopped, and will not resume for decades to come.

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Scientists calculate length of Saturn’s day

Using Cassini data of the rotation rate of Saturn’s rings, scientists have calculated what they think is the precise rotation rate of the planet itself.

Using new data from NASA’s Cassini spacecraft, researchers believe they have solved a longstanding mystery of solar system science: the length of a day on Saturn. It’s 10 hours, 33 minutes and 38 seconds. The figure has eluded planetary scientists for decades, because the gas giant has no solid surface with landmarks to track as it rotates, and it has an unusual magnetic field that hides the planet’s rotation rate.

The answer, it turned out, was hidden in the rings. During Cassini’s orbits of Saturn, instruments examined the icy, rocky rings in unprecedented detail. Christopher Mankovich, a graduate student in astronomy and astrophysics at UC Santa Cruz, used the data to study wave patterns within the rings. His work determined that the rings respond to vibrations within the planet itself, acting similarly to the seismometers used to measure movement caused by earthquakes. The interior of Saturn vibrates at frequencies that cause variations in its gravitational field. The rings, in turn, detect those movements in the field.

…Mankovich’s research, published Jan. 17 by Astrophysical Journal, describes how he developed models of Saturn’s internal structure that would match the rings’ waves. That allowed him to track the movements of the interior of the planet – and thus, its rotation. [emphasis mine]

This work certainly seems ingenious, clever, and somewhat convincing, but I must admit I laughed when I read their estimate of the day length above, to the second. That is ridiculous. Their margin of error cannot possibly be that small. Mankovich has for sure narrowed the uncertainty in the length of Saturn’s day, but forgive me if I remain skeptical as to the precision claimed.

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Summer has finally arrived on Titan’s northern hemisphere

The uncertainty of science: In a review of Cassini data from 2016, scientists have finally identified rain in the northern polar regions of Titan, signaling the onset of summer there.

The whole Titan community has been looking forward to seeing clouds and rains on Titan’s north pole, indicating the start of the northern summer, but despite what the climate models had predicted, we weren’t even seeing any clouds,” said Rajani Dhingra, a doctoral student in physics at the University of Idaho in Moscow, and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. “People called it the curious case of missing clouds.”

Dhingra and her colleagues identified a reflective feature near Titan’s north pole on an image taken June 7, 2016, by Cassini’s near-infrared instrument, the Visual and Infrared Mapping Spectrometer. The reflective feature covered approximately 46,332 square miles, roughly half the size of the Great Lakes, and did not appear on images from previous and subsequent Cassini passes.

Analyses of the short-term reflective feature suggested it likely resulted from sunlight reflecting off a wet surface. The study attributes the reflection to a methane rainfall event, followed by a probable period of evaporation. “It’s like looking at a sunlit wet sidewalk,” Dhingra said.

Though the data somewhat matches their climate models, those models did not predict the rain’s late arrival, which means they need revision. I guarantee that this will not be the last revision, though without an orbiter at Saturn it will probably be decades before we have new data to make that possible.

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Saturn’s rings are dying

Using new ground-based observations, scientists now predict that Saturn’s rings are dying at the fastest predicted rate, and will disappear within 300 million years, at the most.

Dr Tom Stallard, Associate Professor in Planetary Astronomy at the University of Leicester and Dr James O’Donoghue, who studied for his PhD at the University of Leicester, have found that Saturn’s rings are dying at the maximum rate estimated from Voyager 1 and 2 observations made decades ago.

The rings of ice are being pulled into Saturn by gravity as particles of ice under the influence of Saturn’s magnetic field. Dr O’Donoghue, who now works at NASA’s Goddard Space Flight Center in Greenbelt, Maryland said: “We estimate that this ‘ring rain’ drains the equivalent of an Olympic-sized swimming pool from Saturn’s rings in half an hour. The entire ring system will be gone in 300 million years.”

Dr O’Donoghue believes that the rings could even disappear quicker than this. “Add to this the Cassini-spacecraft detected ring-material falling into Saturn’s equator, and the rings have less than 100 million years to live.”

Over the decades I have read numerous papers by scientists saying that rings this bright and large must be a relatively short-lived event, and that we are lucky to have seen them. This research only reinforces this conclusion.

At the same time, we do not yet know the frequency or the cause of the events that give rise such bright rings. It could be that such rings are short-lived, but happen frequently enough that it is still not rare to see them in any solar system. And we won’t know this until we get a more complete census of many solar systems, seen up-close.

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Stripes on Dione

Using data produced by Cassini while orbiting Saturn scientists have discovered long narrow stripes on the moon Dione.

Dione’s linear virgae are generally long (10 to 100s of kilometers), narrow (less than 5 kilometers) and brighter than the surrounding terrains. The stripes are parallel, appear to overlie other features and are unaffected by topography, suggesting they are among the youngest surfaces on Dione.

“Their orientation, parallel to the equator, and linearity are unlike anything else we’ve seen in the Solar System,” Patthoff said. “If they are caused by an exogenic source, that could be another means to bring new material to Dione. That material could have implications for the biological potential of Dione’s subsurface ocean.”

That they cut across the topography implies strongly that they were laid down from above, after the surface irregularities were created.

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Dust storms spotted on Titan

Scientists reviewing Cassini data have identified dust storms for the first time of Saturn’s moon Titan.

When Rodriguez and his team first spotted three unusual equatorial brightenings in infrared images taken by Cassini around the moon’s 2009 northern equinox, they thought they might be the same kind of methane clouds; however, an investigation revealed they were something completely different. “From what we know about cloud formation on Titan, we can say that such methane clouds in this area and in this time of the year are not physically possible,” said Rodriguez. “The convective methane clouds that can develop in this area and during this period of time would contain huge droplets and must be at a very high altitude — much higher than the 6 miles (10 kilometers) that modeling tells us the new features are located.”

The researchers were also able to rule out that the features were actually on the surface of Titan in the form of frozen methane rain or icy lavas. Such surface spots would have a different chemical signature and would remain visible for much longer than the bright features in this study, which were visible for only 11 hours to five weeks.

In addition, modeling showed that the features must be atmospheric but still close to the surface — most likely forming a very thin layer of tiny solid organic particles. Since they were located right over the dune fields around Titan’s equator, the only remaining explanation was that the spots were actually clouds of dust raised from the dunes.

Obviously there are large uncertainties here. Nonetheless, the conclusion is a reasonable one, as it is expected that such dust storms would occur on Titan.

Posted just outside Zion National Park in the town of Springdale.

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Cassini’s last view of Titan

The Cassini science team today released a mosaic of the last images Cassini took of Titan before it crashed into Saturn’s atmosphere four days layer.

The mosaic shows Titan’s north polar region, and shows seas, lakes, and spotty clouds. The lack of clouds is a puzzle to scientists, as they had expected the north polar region to be cloud-covered at this time as summer arrived there, as had been seen at the south pole.

During Titan’s southern summer, Cassini observed cloud activity over the south pole.

However, typical of observations taken during northern spring and summer, the view here reveals only a few small clouds. They appear as bright features just below the center of the mosaic, including a few above Ligeia Mare. “We expected more symmetry between the southern and northern summer,” said Elizabeth (“Zibi”) Turtle of the Johns Hopkins Applied Physics Lab and the Cassini Imaging Science Subsystem (ISS) team that captured the image. “In fact, atmospheric models predicted summer clouds over the northern latitudes several years ago. So, the fact that they still hadn’t appeared before the end of the mission is telling us something interesting about Titan’s methane cycle and weather.”

The truth is we haven’t the slightest idea whether the clouds over the south pole during its previous summer were normal or an aberration. We have barely seen a full year of seasons at Saturn and Titan. To confidently extrapolate any pattern from this slim data is silly.

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Saturn’s polar hexagonal vortex might tower high above clouds

The uncertainty of science: A long term analysis of data from the probe Cassini suggests that Saturn’s north polar hexagonal vortex might tower many miles high above the planet’s clouds.

A new long-term study has now spotted the first glimpses of a northern polar vortex forming high in the atmosphere as Saturn’s northern hemisphere approached summertime. This warm vortex sits hundreds of kilometres above the clouds, in a layer of atmosphere known as the stratosphere, and reveals an unexpected surprise. “The edges of this newly-found vortex appear to be hexagonal, precisely matching a famous and bizarre hexagonal cloud pattern we see deeper down in Saturn’s atmosphere,” says Leigh Fletcher of the University of Leicester, UK, lead author of the new study.

“While we did expect to see a vortex of some kind at Saturn’s north pole as it grew warmer, its shape is really surprising. Either a hexagon has spawned spontaneously and identically at two different altitudes, one lower in the clouds and one high in the stratosphere, or the hexagon is in fact a towering structure spanning a vertical range of several hundred kilometres.”

There are many uncertainties here. For one thing, we have not yet even observed Saturn from up close through a complete year. We might be seeing random weather events having nothing to do with the gas giants overall planetary weather patterns.

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The aurora of Saturn

Cool movie time! Using the Hubble space telescope scientists have compiled an animation showing the changes in Saturn’s north pole aurora over time.

In 2017, over a period of seven months, the NASA/ESA Hubble Space Telescope took images of auroras above Saturn’s north pole region using the Space Telescope Imaging Spectrograph. The observations were taken before and after the Saturnian northern summer solstice. These conditions provided the best achievable viewing of the northern auroral region for Hubble.

…The images show a rich variety of emissions with highly variable localized features. The variability of the auroras is influenced by both the solar wind and the rapid rotation of Saturn, which lasts only about 11 hours. On top of this, the northern aurora displays two distinct peaks in brightness — at dawn and just before midnight. The latter peak, unreported before, seems specific to the interaction of the solar wind with the magnetosphere at Saturn’s solstice.

The animation of all the images is embedded below. At the link is a second video showing the aurora in close-up

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Global mosiacs of Titan in infrared

Titan in infrared

The Cassini science team today released global infrared mosaics of Titan, created from images accumulated during the more than 100 fly-bys of the moon during the spacecraft’s thirteen years in orbit around Saturn.

The image on the right, cropped and reduced in resolution to post here, is only one such global mosaic. Go to the story to see them all.

Making mosaics of VIMS images of Titan has always been a challenge because the data were obtained over many different flybys with different observing geometries and atmospheric conditions. One result is that very prominent seams appear in the mosaics that are quite difficult for imaging scientists to remove. But, through laborious and detailed analyses of the data, along with time consuming hand processing of the mosaics, the seams have been mostly removed. This is an update to the work previously discussed in PIA20022.

Any full color image is comprised of three color channels: red, green and blue. Each of the three color channels combined to create these views was produced using a ratio between the brightness of Titan’s surface at two different wavelengths (1.59/1.27 microns [red], 2.03/1.27 microns [green] and 1.27/1.08 microns [blue]). This technique (called a “band-ratio” technique) reduces the prominence of seams, as well as emphasizing subtle spectral variations in the materials on Titan’s surface. For example, the moon’s equatorial dune fields appear a consistent brown color here. There are also bluish and purplish areas that may have different compositions from the other bright areas, and may be enriched in water ice.

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Complex carbon molecules from within Enceladus

Scientists have determined, using Cassini data, that there are complex carbon molecules spewing from the tiger stripes on Saturn’s moon Enceladus.

Putting it all together, the scientists concluded that the Cassini spacecraft was encountering dust particles rich in carbon in large, complex “macromolecular structures”. The only place this material could have come from was the interior of Enceladus, from which ice, dust and gas is jetting out in geyser-like plumes. These plumes are fed by vapours escaping from a sub-surface ocean.

“So this is a direct sample of the Enceladus ocean,” Khawaja says.

What exactly the newly discovered organic materials are is open for debate, although Khawaja believes they most likely are made of large numbers of ring-like structures cross-linked by hydrocarbon chains. An important hint comes from the fact that the organic-rich grains don’t contain much water, implying that the materials in them don’t easily mix with water. Khawaja hypothesises that they formed deep inside Enceladus, then rose to the top of its underwater ocean, where they formed a thin film akin to an earthly oil slick.

Just to be very clear, they have not discovered life. What they have found however increases the chances that there is life within Enceladus’s underground ocean.

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Methane detected on Enceladus could come from microbes

The uncertainty of science: New research has found that the methane that Cassini detected being released from Enceladus’s interior could conceivably come from at least one Earth-type microbe.

Using various mixtures of gases held at a range of temperatures and pressures in enclosed chambers called “bioreactors,” Rittmann and his co-authors cultivated three microorganisms belonging to the oldest branch of Earth’s tree of life, known as Archaea. In particular, they focused on Archaean microbes that are also methanogens, which are able to live without oxygen and produce methane from that anaerobic metabolism. The team examined the simplest types of microbes, which could be the primary producers of methane at the base of a possibly more complex ecological food chain within the moon.

They tried to simulate the conditions that could exist within and around Enceladus’s hydrothermal vents, which are thought to resemble those found at a few deep-sea sites on Earth, often near volcanically active mid-oceanic ridges. According to their tests, only one candidate, the deep-sea microbe Methanothermococcus okinawensis, could grow there—even in the presence of compounds such as ammonia and carbon monoxide, which hinder the growth of other similar organisms.

There are a lot of fake news stories today trumpeting this result as proof that alien microbes can exist on Enceladus. The data does no such thing. All it shows that one methane producing microbe could possibly live in an environment that researchers guess might somewhat resemble the situation on Enceladus. However, as the article admits,

Scientists do not really know the precise conditions on Enceladus yet, of course. And in any case it is possible any life there, if it exists, is nothing like any DNA-based organism on our planet, rendering our Earth-based extrapolations moot. What’s more, these findings only show microbial life might exist in one particular subset of possible environments within the moon’s dark ocean.

This result is interesting, but it really proves nothing about Enceladus itself.

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Titan’s liquid hydrocarbon seas have a global sea level

New research using Cassini data has revealed that the liquid hydrocarbon oceans of Saturn’s moon Titan have a global sea level, with some small lakes perched at higher elevations.

The new study suggests that elevation is important because Titan’s liquid bodies appear to be connected under the surface in something akin to an aquifer system at Earth. Hydrocarbons appear to be flowing underneath Titan’s surface similar to the way water flows through underground porous rock or gravel on Earth, so that nearby lakes communicate with each other and share a common liquid level.

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Saturn’s rings are very young

Data from Cassini’s last ring-diving orbits has now strengthened the hypothesis that Saturn’s rings formed very recently, just a few hundred million years ago.

Saturn acquired its jewels relatively late in life. If any astronomers had gazed at the sky in the time of the dinosaurs, they might have seen a bare and boring Saturn.

It was then that some sort of catastrophe struck the gas giant. Perhaps a stray comet or asteroid struck an icy moon, tossing its remnants into orbit. Or maybe the orbits of Saturn’s moons somehow shifted, and the resulting gravitational tug-of-war pulled a moon apart. However it happened, two new lines of evidence from Cassini make it clear that the rings were not around in the early days of the solar system 4.5 billion years ago, as scientists had long believed, says Jeff Cuzzi, a ring specialist at NASA’s Ames Research Center in Mountain View, California. “It rules out the primordial ring story,” Cuzzi says. “That’s what it looks like to me.”

At the moment there is no consensus on what might have caused the rings formation so recently.

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Cassini’s last full mosaic of Saturn and its moons

Cassini's last full mosaic of Saturn

Cool image time! The image above, cropped and reduced in resolution to show here, was created by Cassini from 42 images taken on September 13, 2017, two days before the spacecraft dived into Saturn to end its mission.

Be sure to take a look at the full image. It shows six of Saturn’s moons, as well as many stars.

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Billionaire Yuri Milner considering funding mission to Enceladus

Capitalism in space: Billionaire Yuri Milner, who already funds several astronomy projects aimed at interstellar travel, is now considering funding a planetary probe to the Saturn moon Enceladus.

At the moment all he is doing is holding workshops with scientists and engineers to see if such a mission can be done for an amount he can afford. Considering that Elon Musk’s first concept to send a private probe to Mars, before SpaceX existed, was stopped because of high launch costs, thus becoming the inspiration for SpaceX itself in order to lower those costs, Milner’s private effort might actually be affordable now.

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The glory of Cassini’s Saturn

The glory of Saturn

Cool image time! The image on the right, reduced in resolution to post here, was taken by Cassini on August 17, 2017, one month before the spacecraft dived into Saturn to end its mission.

This view looks toward the sunlit side of the rings from about 19 degrees above the ringplane. The image was taken in green light with the Cassini spacecraft wide-angle camera on Aug. 12, 2017. Pandora was brightened by a factor of 2 to increase its visibility.

The view was obtained at a distance to Saturn of approximately 581,000 miles (935,000 kilometers) from Saturn. Image scale is 35 miles (56 kilometers) per pixel. The distance to Pandora was 691,000 miles (1.1 million kilometers) for a scale of 41 miles (66 kilometers) per pixel.

The moon Pandora can be seen in the full resolution image just beyond the outermost ring near the top of the screen.

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New findings from Cassini’s final months

Link here. Among a bunch of other interesting results, this one I found the most tantalizing:

The spacecraft’s Ion and Neutral Mass Spectrometer (INMS) returned a host of first-ever direct measurements of the components in Saturn’s upper atmosphere, which stretches almost to the rings. From these observations, the team sees evidence that molecules from the rings are raining down onto the atmosphere. This influx of material from the rings was expected, but INMS data show hints of ingredients more complex than just water, which makes up the bulk of the rings’ composition. In particular, the instrument detected methane, a volatile molecule that scientists would not expect to be abundant in the rings or found so high in Saturn’s atmosphere.

The results generally leave behind more questions than answers, but that is exactly why exploring the universe is so much fun.

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Storms on Titan dump a lot of liquid methane, quickly

A new climate model for Titan that suggests the planet’s methane rainstorms occur about once a Saturn year (29.5 years) and at about 60 degree latitude correlates with Cassini surface data that found a high concentration of alluvial fans at that latitude.

“The most intense methane storms in our climate model dump at least a foot of rain a day, which comes close to what we saw in Houston from Hurricane Harvey this summer,” said Mitchell, the principal investigator of UCLA’s Titan climate modeling research group.

Sean Faulk, a UCLA graduate student and the study’s lead author said the study also found that the extreme methane rainstorms may imprint the moon’s icy surface in much the same way that extreme rainstorms shape Earth’s rocky surface. On Earth, intense storms can trigger large flows of sediment that spread into low lands and form cone-shaped features called alluvial fans. In the new study, the UCLA scientists found that regional patterns of extreme rainfall on Titan are correlated with recent detections of alluvial fans, suggesting that they were formed by intense rainstorms.

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The kittens of Saturn’s rings

The scientists who used Cassini to identify about 60 transient clumps in Saturn’s rings have dubbed them “kittens” and have been naming them appropriately.

Saturn’s kittens are a group of small clumps and baby moons, or moonlets, that occupy the planet’s F ring. Like the rest of Saturn’s rings, this thin outer ring is made up of countless particles that range in size. When enough of those particles bump into one another and stick together, they aggregate into larger clumps — and become eligible for a kitten name.

So far, the list of Saturn’s kitten names includes several classics, like Fluffy, Garfield, Socks and Whiskers. These are unofficial nicknames for more-complicated (and less adorable) official titles like “Alpha Leonis Rev 9” (aka, Mittens). The technical names for these features come from events called stellar occultations, during which Cassini was able to detect the little clumps. In a stellar occultation, a star passes behind Saturn’s rings from Cassini’s point of view.

Most of these clumps will likely never be found again, so their unofficial kitten names are essentially just for fun.

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Cassini’s last image of Iapetus

Iapetus

The image on the right is a cropped and scaled up version of one of Cassini’s last images of Saturn’s moon, Iapetus.

The moon is unique in that its east and west hemispheres have completely opposite albedos, with one being very dark and the other very bright. It also has a very distinctive large crater, seen in this image. Scientists do not quite understand what causes the dichotomy, though they have models that partly explain it, partly from material being deposited on the moon’s leading hemisphere combined with the temperature differences at different latitudes.

The cause of the extreme brightness dichotomy on Iapetus is likely to be thermal segregation of water ice on a global scale. Thermal effects are usually expected to act latitudinally. That is, polar areas are colder than equatorial terrain in most cases due to the more oblique angle of the solar irradiation. Therefore, an additional process is required to explain the longitudinal difference as well. In one model, dark, reddish dust coming in from space and preferentially deposited on the leading side forms a small, but crucial difference between the leading and trailing hemispheres, which is sufficient to allow the thermal effect to evaporate the water ice on the leading side completely, but only marginally on the trailing side.

It was this moon’s strange dichotomy that had Arthur Clarke use it in 2001: A Space Odyssey. While Cassini’s images clearly prove that the brightness difference was not created by an alien civilization, as imagined by Clarke, those images have not really provided us a full explanation for its cause. The uncertainty of science marches on!

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