Using six years of archival data from the Cassini Saturn orbiter, scientists now think Saturn’s magnetic field is lopsided, pulled sideways due to the planet’s very fast rotation as well as the material that surrounds the ringed planet.

The graphic to the right, Figure 4 from the research paper [pdf], compares the Earth’s symmetric magnetic field (top) with that of Saturn’s (bottom). From the press release:

The team found that the cusp was dragged to the right as viewed from the Sun, and was located most often between 1:00 and 3:00 (as it might appear on a clockface), compared to 12:00 as it would be on Earth.

The researchers said this was likely because of Saturn’s extremely fast rotation (a Saturn day is 10.7 hours) and the heavy “soup” of plasma (ionised gas) it pulls around it, a product of gases emitted by Saturn’s moons, especially Enceladus. Together, these are thought to drag the magnetic field lines to the right. But more simulations are needed to confirm this interpretation.

When the solar wind hits the Earth’s magnetic field lines at the cusp, that wind is funneled down along those lines to the poles, where it produces the aurora. This new analysis at Saturn will help scientists better understand the behavior of Saturn’s aurora, which is made even more complex by the planet’s many moons.

Cool image time! The image to the right, reduced and sharpened to post here, was taken on September 10, 2007 by the Saturn orbiter Cassini as it made its first close fly-by of the moon Iapetus, from a distance of about 45,000 miles.

Iapetus, about 912 miles in diameter, is one of the strangest objects in the solar system. As it orbits Saturn, its leading hemisphere is very dark, covered with almost pitch black material, while its trailing hemisphere is very bright. This picture captures a bit of both, with the dark leading hemisphere visible along the right edge.

In many places, the dark material–thought to be composed of nitrogen-bearing organic compounds called cyanides, hydrated minerals and other carbonaceous minerals–appears to coat equator-facing slopes and crater floors. The distribution of this material and variations in the color of the bright material across the trailing hemisphere will be crucial clues to understanding the origin of Iapetus’ peculiar bright-dark dual personality.

There are several theories to explain the planet’s strange ying-yang two-tone coloration. One suggests it is material thrown off by other Saturn moons that Iapetus sweeps up. Other theories suggest the planet’s orbit itself causes the two hemispheres to have different temperatures, allowing material to sublimate off the dark side and to the bright side.

No theory is presently accepted. Nor does any explain the data fully.

Tomorrow I’ll post a most intriguing close-up of Iapetus taken by Cassini during that 2007 fly-by.

Cool image time! When Voyager-1 did its fly-by of Saturn in December 1980, its cameras captured something in the gas giant’s rings that no one had predicted or expected, spokes of brightness pointing outward along the surface of the rings at right angles to the planet. Even more puzzling, these spokes actually appeared to rotate around Saturn, always pointing away from it.

The picture to the right, cropped, reduced, and enhanced to post here, was taken on March 7, 2007 by the Saturn orbiter Cassini. It shows a close-up of one such spoke, though in this case it is bent. From the press release:

A bright spoke extends across the unilluminated side of Saturn’s B ring about the same distance as that from London to Cairo. The background ring material displays some azimuthal (i.e., left to right) asymmetry. The radial (outward from Saturn) direction is up in this view. A noticeable kink in the spoke occurs very close to the radius where ring particles orbit the planet at the speed of Saturn’s magnetic field. Such a connection is most intriguing to scientists studying these ghostly ring phenomena.

If gravity alone were affecting the spoke material, there would be no kink and the entire spoke would be angled toward right, like the bottom portion. That it bends to the left above the kink indicates that some other force, possibly related to the magnetic field, is acting on the spoke material. The shape might also indicate that the spoke did not form in a radial orientation, thus challenging scientists’ assumptions about these features.

In other words, the spokes exist because of multiple factors, some still unknown, that cause these streaks of brightness in the rings. For some reason, the millions of tiny ice particles that comprise the rings are brightened along these spokes, and it isn’t just gravity that is causing it.

Cool image time! The picture to the right, cropped and enhanced to post here, was taken on December 23, 2005 by Cassini as it orbited Saturn.

The larger cratered moon is Mimas, known best for the single giant crater that dominates one hemisphere. I have not been able to identify the brighter but smaller moon.

Note the pattern within the largest bright central ring in the background. It is possible this is an optical illusion, but it is also possible this pattern is inherent in the ring itself. Other images show similar patterns that scientists have concluded were real.

This image was part of a set of eight images all taken in the space of less than two minutes, as the smaller moon moved from the lower left to the upper right and was eclipsed by Minas as it did so. Below are four of those pictures, showing the sequence.

For original images, go here, here,
here, and here.

The four images to the right, cropped and reduced to post here, were all taken on December 12, 2005 over a span of less than two minutes (see here, here, here, and here).

As far as I can determine after some extensive searching, it appears the Cassini science team never issued a press release about this particular eclipse. If so, this means this is the first time these images have been highlighted in the general press.

The speed in which the small moon moves is an illusion. The camera was pointed at Mimas, so it remains still as the scenery around it shifts. In addition, the moons are not as close to each other as this sequence suggests.

That other moon appears to orbit closer to the rings. It also appears brighter with fewer craters. If anyone can identify it please say so in the comments.

Cool image time! On December 19, 2015 the Saturn orbiter Cassini made its last close fly-by of the moon Enceladus, known best for the many geysers detected on its surface venting water and other carbon-based materials.

The picture to the right, reduced and enhanced to post here, shows that the entire face of this
Saturn’s moon Enceladus, as seen during that fly-by. The moon itself is only about 310 miles across.

Its icy surface is evident, as are the many fractures, some meandering almost like rivers. Interestingly, for some reason there are a lot more craters in the lower hemisphere, while the upper hemisphere is more completely covered with fractures.

The black outline indicates the approximate area captured by the two close-up images below.

Close-up of Enceladus’ equatorial regions. Click
here and here for original images.

The two pictures to the right, reduced and cropped to post here, were taken (here and here) only a few minutes before Cassini made its closest approach, 3,106 miles from the surface.

Based on data obtained during Cassini’s fly-bys of Enceladus, scientists believe a liquid ocean exists beneath the surface. And if you have ever looked at images of the Arctic ice coverage on the North Pole, this surface will look somewhat familiar, reinforcing that conclusion. Over time the Arctic cap of ice cracks and shifts as it floats on the liquid, causing fractures as well as curving lines.

It sure does appear the same thing is happening on Enceladus.

The presence of only a few craters suggests however this surface does not change quickly. It does change, though, wiping out earlier impact evidence.

Using data collected by the orbiter Cassini while it orbited Saturn more than a decade ago, scientists now think they have mapped out how the moon Enceladus interacts with Saturn’s magnetic field and helps create an aurora in Saturn’s polar regions.

You can read the paper here. The artist rendering to the right comes from the press release, and shows that interaction. From that release:

The study, published in the Journal of Geophysical Research: Space Physics, shows how wave structures, known as ‘Alfvén wings’, travel like vibrations on a string along magnetic field lines connecting Enceladus to Saturn’s pole. The initial ‘main’ Alfvén wing is reflected back-and-forth both by Saturn’s ionosphere and the plasma torus that encircles Enceladus’s orbit, resulting complex and structured system. By using a multi-instrumental approach, researchers were able to show that the influence of Enceladus extends over a record distance of over 504,000 km – more than 2,000 times the moon’s radius.

…As well as the large-scale structures, the team found evidence that turbulence teases out the waves into filaments within the main Alfvén wing. This fine-scale structure helps the waves bounce off Enceladus’s plasma torus and reach the high-latitudes in Saturn’s ionosphere where auroral features associated with the moon form.

The white haze below Enceladus in the graphic represents the material that comes out of the “tiger stripe” fractures near its south pole.

Cool image time! My exploration of the Cassini image archive continues. The picture to the right, reduced and enhanced to post here, was taken on May 2, 2005 by Cassini soon after it moved into a close orbit of Saturn where it could get high resolution images of Saturn’s rings. This is one of the first.

This is also a raw image that has not been calibrated or validated, to use the science team’s terms. Thus, the white dots scattered across the image could be artifacts that need to be cleaned up, not examples of Saturn’s many moons.

Regardless, the image illustrates the incredible delicacy of these rings, despite the fact that they are gigantic, spanning almost 45,000 miles in width, with a thickness ranging from 30 to 1,000 feet. And yet, there are so many distinct rings they almost resemble an old-fashioned vinyl record.

Cool image time! The picture to the right, cropped and reduced to post here, was taken on April 13, 2017 by the orbiter Cassini as it began it last close loops around Saturn before diving into its atmosphere to burn up.

Those close loops allowed it to get good close-up images of a few of the tiny moons that orbit in or close to the gas giant’s rings. On the right is one of those pictures, of the moon Atlas, taken from a distance of about 10,000 miles.

The moon’s weird ravioli shape is thought to be caused by the accretion of dust and ice from the nearby rings along Atlas’s equator.

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.”

Atlas itself is about 25 miles wide and about 11.5 miles thick, at its thickest point. I suspect if you tried to walk on it you would sink into the accumulated dust and ice, as it is likely no more dense as newly fallen snow.

Cool image time! Rather than posting another Mars orbital image, I decided today to delve into the archive of pictures taken by the Cassini orbiter during the thirteen years it circled Saturn, from 2004 until 2017. The picture to the right, cropped to post here, was released on December 14, 2015, and is just one example of the many breath-taking photographs that the Cassini science team took during that mission. From the caption:

Like a cosmic bull’s-eye, Enceladus and Tethys line up almost perfectly for Cassini’s cameras. Since the two moons are not only aligned, but also at relatively similar distances from Cassini, the apparent sizes in this image are a good approximation of the relative sizes of Enceladus (313 miles across) and Tethys (660 miles across).

This view looks toward the un-illuminated side of the rings from 0.34 degrees below the ring plane. The image was taken in red light with the Cassini spacecraft narrow-angle camera on Sept. 24, 2015.

The image was obtained at a distance of approximately 1.3 million miles from Enceladus. Image scale on Enceladus is 7 miles per pixel. Tethys was at a distance of 1.6 million miles with a pixel scale of 10 miles per pixel.

Enceladus is in the foreground, and is the planet that has what scientists have labeled tiger stripe fractures that vent water and other material, including carbon molecules.

Using archival radar data obtained by the Saturn orbiter Cassini from one of its many fly-bys of the moon Titan, scientists now believe that most of the high northern latitude lakes on Titan are mostly made of pure methane, not ethane, and that their surface is remarkably calm and smooth. From the abstract:

During its 119th flyby of the moon, the Cassini spacecraft conducted a bistatic radar experiment observing a group of seven lakes in Titan’s Northern Lake District located between (72°N, 143°W) and (77°N, 131°W). The orbiter transmitted a continuous-wave signal at a wavelength of 3.56 cm (X-band) toward Titan’s surface, targeting the moving specular reflection point between the spacecraft and Earth. As the antenna footprint intercepted the liquid surfaces of the lakes, distinct specular reflections were detected on Earth by the 70-m antenna at NASA’s Canberra Deep Space Network complex. Analysis of these reflections shows that all seven lakes exhibit similar dielectric properties—linked to their composition—and surface roughness, suggesting they are methane-dominated and may have a few millimeters of surface roughness. [emphasis mine]

The highlighted phrase underscores what previous data had shown, that the methane lakes of Titan are remarkably calm, almost to the point of absurdity.

The image to the right, figure 1 of the paper, shows the track of this radar observation. Based on this data as well as data obtained during a later fly-by of another nearby lake, the scientists posit that all the lakes in this region are likely similar, mostly filled with methane having a surface with barely no ripples at all.

This information is crucial for the planned Dragonfly mission, that will fly over and onto Titan’s methane lakes, though not in the high latitudes but in its equatorial regions. Knowing the conditions as best as possible will increase the odds that this very risky mission will succeed.

Cool image time! Rather than post another Mars image, I decided today to dig into the archive left from the Cassini orbiter that circled Saturn from July 1, 2004 until September 15, 2017. The picture to the right, cropped to post here, was taken on September 13, 2017, only two days before the orbiter burned up in Saturn’s atmosphere. From the caption:

This image of Saturn’s outer A ring features the small moon Daphnis and the waves it raises in the edges of the Keeler Gap. The image was taken by NASA’s Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth. The view was taken in visible light using the Cassini spacecraft wide-angle camera at a distance of 486,000 miles from Saturn. Image scale is 2.7 miles [per pixel].

The moon is traveling downward in this image. As it moves past the outer ring, its gravity causes that edge to ripple, producing the waves.

The scale will give you an idea of how big the rings of Saturn are. The Keeler Gap is at the outer edge of the A ring of Saturn, which is the outermost ring that is clearly visible using ordinary amateur telescopes. That edge however is more than 90,000 miles from Saturn. And grayish bands to the right of Daphne and the Keeler Gap are only the outer half of the A ring, which is by itself about 9,000 miles wide.

Cool image time! As most of the new cool images coming down from space seem mostly limited to Mars and deep space astronomy, I decided today to dig into the archive of the probe Cassini, which orbited Saturn from July 1, 2004 until September 15, 2017, when it was sent plunging into the gas giant’s atmosphere.

The picture to the right heralded the start of that mission, in that it was taken on February 19, 2004, a little over four months before the spacecraft fired its engines and entered orbit. I have rotated the image and cropped it to post here.

When Cassini snapped this picture it was just approaching the gas giant. The image itself is relatively small, with the resolution also relatively poor. You can see one of Saturn’s moons above the planet, but I can’t tell you which one. As noted at the webpage, this is a raw image that has not been “validated or calibrated.”

While not up to the amazing standard exhibited by Cassini’s images during its thirteen year stay at Saturn, it gave us a flavor of the wonders to come. Of all the planets, Saturn might be the most beautiful.

A new analysis of the archived Cassini data taken when the spacecraft flew through the plumes of the Saturn moon Enceladus in 2008 has revealed a number of new organic molecules (not life but carbon-based) that suggest the chemistry of the moon of Saturn is far more complex that expected.

You can read the paper here. From the abstract:

Here we present a comprehensive chemical analysis of organic-bearing ice grains sampled directly from the plume during a Cassini fly-by of Enceladus (E5) at an encounter speed of nearly 18 km [per second]. We again detect aryl and oxygen moieties in these fresh ice grains, as previously identified in older E-ring grains. Furthermore, the unprecedented high encounter speed revealed previously unobserved molecular fragments in Cosmic Dust Analyzer spectra, allowing the identification of aliphatic, (hetero)cyclic ester/alkenes, ethers/ethyl and, tentatively, N- and O-bearing compounds. These freshly ejected species are derived from the Enceladus subsurface, hinting at a hydrothermal origin and involvement in geochemical pathways towards the synthesis and evolution of organics.

In other words, this data further suggests there exists an underground ocean inside Enceladus, and that ocean has a lot of complex organic chemistry energized by the planet’s internal heat and the tidal forces imposed by Saturn’s gravity.

This is not the first time scientists have reviewed archived Cassini data of these plumes and found new molecules. It is simply a closer look at earlier analyses in 2018 and 2019.

This data has not discovered life, but it suggests that life is certainly possible within that proposed underground ocean. At a minimum, the chemistry there will be very complex and alien.

The uncertainty of science: Scientists doing computer simulations now posit that Saturn’s rings are not young, between 100 to 400 million years old as has been believed for the last few decades, but formed instead when Saturn formed, 4.6 billion years ago.

You can read their paper here [pdf].

The young age had been based on data from the Cassini orbiter, which showed the ring particles to be very bright and clean. If old those particles would have been darker as they accumulated dust over time on their surface. The new computer simulations suggest a process whereby those particles get “cleaned,” thus making it possible for the rings to be very old, possibly as old as Saturn itself.

Must I point out the uncertainties? The paper itself admits in its abstract “uncertainties in our models that assume no porosity, strength, or ring particle granularity.” Seems these assumptions make the conclusions very uncertain indeed.

Then again, the previous young estimates of the age of the rings had many similar assumptions and uncertainties. Essentially, we don’t have enough information to make any definitive determinations.

[I]n 2014, a team that included Lainey and that was led by Radwan Tajeddine, an astronomer then at the Paris Observatory, analysed images taken by NASA’s Cassini spacecraft, which explored Saturn and its moons between 2004 and 2017. By studying how the 400-kilometre-wide Mimas wobbled in its orbit around Saturn, the researchers concluded that it had either a buried ocean or a rugby-ball-shaped core. As more scientists studied how an ocean could have formed and evolved, it became harder to explain the geology of Mimas without invoking an ocean.

In the 2024 study, Lainey and his colleagues seem to have nailed the case. They went further than they had in 2014, by analysing not just the orbit’s wobble but also how Mimas’s rotation around Saturn changed over time. The team combined Cassini observations with simulations of Mimas’s interior and its orbit to conclude that there must be an ocean 20–30 kilometres below Mimas’s surface.

The journal Nature published the paper, and the link above goes to an article in Nature describing the results, with a headline “The Solar System has a new ocean — it’s buried in a small Saturn moon.” This is very poor journalism, but very typical these days from Nature. Nowadays that journal routinely pushes the results it publishes with great certainty, even if the data is quite uncertain.

And these results are quite uncertain. They are based on computer simulations using orbital data only. No data from Mimas itself is involved. While that orbital data and computer models might suggest an underground ocean that is very young, that is the best it does, “suggest.” Without question this conclusion is very intriguing, but it should not be treated as a discovery, only a theory that still needs confirmation with much better data.

Cool image time! Though the Saturn orbiter Cassini is long gone, having been sent into Saturn’s atmosphere to burn up in 2017, its image archive of magnificent pictures is still available to peruse. To encourage others to do so, NASA today issued a series of press releases, listing the spacecraft’s top ten pictures from 2011, 2012, 2013, 2014, and 2015.

The picture to the right, cropped, reduced, and sharpened to post here, comes from the 2011 collection and was taken on June 18, 2011. It shows a close-up of 21-mile-wide Helene, one of Saturn’s many many moons and only discovered in 1980. Back in 2010 I featured another Cassini image of Helene, but that picture did not reveal the small surface features seen in the photo to the right.

The light and dark streaks probably indicate dust flowing downhill on the surface. Though the gravity of this object is tiny, it will be enough for dust to act like almost like a liquid, flowing down grade and then pooling in the central pond at the lowest point near the center of the picture. That process is so much like liquid flowing that it appears to have even eroded gullies on slopes near the top and bottom of the picture.

Side note: NASA’s “Science Editorial Team” also issued a press release today that falsely and ignorantly claimed these releases were “to celebrate 10 years since arriving at Saurn,” implying that Cassini arrived in 2013 and is still functioning.

The problem is that Cassini arrived in orbit around Saturn in 2004 and as I noted above ended its mission in 2017. It thus appears that the NASA Science Editorial Team is unable to do even one five-second web search to find out what really happened.

Just another data point indicating the dark age we now live in.

The small moon is known to possess a subsurface ocean, and water from that ocean erupts through cracks in Enceladus’ icy crust as geysers at its south pole, creating a plume. The plume then feeds Saturn’s E ring (a faint ring outside of the brighter main rings) with icy particles.

During its mission at the gas giant from 2004 to 2017, Cassini flew through the plume and E ring numerous times. Scientists found that Enceladus’ ice grains contain a rich array of minerals and organic compounds – including the ingredients for amino acids – associated with life as we know it.

Phosphorus, the least abundant of the essential elements necessary for biological processes, hadn’t been detected until now. The element is a building block for DNA, which forms chromosomes and carries genetic information, and is present in the bones of mammals, cell membranes, and ocean-dwelling plankton. Phosphorus is also a fundamental part of energy-carrying molecules present in all life on Earth. Life wouldn’t be possible without it.

“We previously found that Enceladus’ ocean is rich in a variety of organic compounds,” said Frank Postberg, a planetary scientist at Freie Universität Berlin, Germany, who led the new study, published on Wednesday, June 14, in the journal Nature. “But now, this new result reveals the clear chemical signature of substantial amounts of phosphorus salts inside icy particles ejected into space by the small moon’s plume. It’s the first time this essential element has been discovered in an ocean beyond Earth.”

You can read the paper here. It is very important to emphasize that though phosphorus is essential for life, life in the underground ocean of Enceladus has not been discovered. The scientists have merely found evidence of this specific ingredient needed for life, suggesting that these ingredients are common in our solar system. Going from a list of ingredients to a finished dish one can eat is something else entirely.

From 2004 to 2017, the team used an instrument called the Cosmic Dust Analyzer aboard NASA’s late Cassini spacecraft to analyze specks of dust flying around Saturn. Over those 13 years, the researchers collected just 163 grains that had originated from beyond the planet’s close neighborhood. But it was enough. Based on their calculations, Saturn’s rings have likely been gathering dust for only a few hundred million years.

Though I cannot cite the earlier research, I distinctly remember a study from about a decade ago that posited the rings being young, only a few hundred million years old. This research confirms this conclusion, and likely firms up the theory considerably.

Then, for the second half of the movie Gil used Cassini images taken when in orbit around Saturn to show the moon Titan moving across the rings of Saturn.

I have embedded this short video below. If I had posted this back in 2018, I don’t remember. No matter. It is amazing enough to watch again.

Hat tip BtB’s stringer Jay.

Using archival data from the Cassini orbiter that mapped ripples in the rings of Saturn, scientists have produced a model of Saturn’s core that suggests it is a slushy soup that as it sloshes about shifts the gas giant’s gravitational field.

By using the famous rings like a seismograph, scientists studied processes in the planet’s interior and determined that its core must be “fuzzy.” Instead of a solid sphere like Earth’s, the core of Saturn appears to consist of a ‘soup’ of rocks, ice and metallic fluids that slosh around and affect the planet’s gravity.

…Not only does the planet’s core seem sludgy, it also appears to extend across 60% of the planet’s diameter, making it much larger than previously estimated. The analysis showed that Saturn’s core might be about 55 times as massive as the entire planet Earth. Of the total mass of the core, 17 Earth masses are made of ice and rock, with the rest consisting of a hydrogen and helium-based fluid, the study suggests.

The image above was taken in 2017, and shows both a density wave in the rings (the parallel lines in the center) caused by a Saturn moon, and numerous “propellers”, small distortions in the rings caused by slightly larger objects.

Their effort was an attempt to identify an unknown spectroscopy absorption feature at a specific wavelength.

In comparison to chloromethane, the production of hydrazine monohydrate was easier to explain due to chemical reactions involving water-ice and ammonia or delivery from Titan’s nitrogen rich atmosphere. Elowitz et al. considered the possibility of contamination of the UVIS data by a hydrazine propellant from the Cassini spacecraft, although it was highly unlikely since the hydrazine thrusters were not used during icy satellite flybys.

The team confirmed the specific signature of a 184-nm feature on Rhea’s surface using the UV spectrometer observations made by the Cassini spacecraft. In addition to that, the irradiation of ammonia by charged particles from Saturn’s magnetosphere induced the dissociation of ammonia molecules to form diazene and hydrazine. The source of ammonia on Rhea could be primordial, incorporated into its interior during formation and brought to the surface within a period of endogenic activity, as evident in Cassini ISS imagery, although ammonia was unlikely to survive indefinitely on the surface. The team suggest further analysis to understand the potential for satellite-to-satellite transfer of materials across Titan’s atmosphere to explain the presence of hydrazine monohydrate on Rhea.

Though useful as a fuel, its poisonous nature will make any exploration of these moons very hazardous, and will also likely make its usefulness difficult initially in that exploration

The uncertainty of science: In a new paper scientists have taken the radar data from the more than 120 fly-bys by Cassini of Titan to map out the estimated depths for several of Titan’s seas, using that data to also better constrain the make-up of those seas. From their abstract:

Our analysis reveals that the seafloor at the center of Moray Sinus—an estuary located at the northern end of Kraken Mare, is up to 85 m deep. The radar waves are absorbed to an extent such that the liquid composition is compatible with 70% methane, 16% nitrogen, and 14% ethane (assuming ideal mixing). The analysis of the altimetry data in the main body of Kraken Mare showed no evidence for signal returns from the sea floor, suggesting the liquid is either too deep or too absorptive for Cassini’s radio waves to penetrate. However, if the liquid in the main body of Kraken Mare is similar in composition to Moray Sinus, as one would expect, then its depth exceeds 100 m.

The image above, cropped and reduced to post here, is figure two from the paper. The horizontal red line indicates a radar track, with the resulting depths shown in the profile along the bottom. The scientists think the first flat signal, labeled A, is a now dry seabed on land, while B represents Arnar Sinus, C the bay south of the large landform dubbed Mayda Insula, and D the estuary dubbed Moray Sinus. All these bays and estuaries flow into Kraken Mare, the largest sea on Titan.

What the data suggests is that these alien seas of methane, nitrogen, and ethane are very deep, and that the depth drops quickly from the shoreline. This conclusion matches earlier data of Titan’s rivers, which often flow through spectacularly deep slot canyons. In both cases, it appears the strange liquid “water” of Titan is aggressively erosive, and carves deeply wherever it is found.

The data also suggests that the surface of these seas might be coated with a material that has mechanical properties similar to terrestrial snow.

While the deposits on Titan would not be snow composed of water ice, the mechanical properties leading to high porosity might be analogous. … Wind stress, tidal currents in the presence of topographic obstacles, and/or convection by solar heating would then cause agglomerates of large particles and polymer chains to move upward in the liquid and be maintained in the mixed layer near the surface of the sea.

In other words, if there is a coating on the surface of these alien seas, it did not arrive by snowfall, but instead precipitated upward from the sea’s depths to gather on the surface. In many ways this surface material and its formation reminds me of the calcite rafts you sometimes see forming on ponds within cave. The water is so saturated with calcium calcite that some precipitates out to float on the surface. Given enough time those rafts can thicken and form a hard solid coating.

While there are some vague similarities, I am certain that the material on Titan is different. We just don’t know enough to pin down exactly how different it is.

Lakes on Saturn’s moon Titan, composed of methane, ethane, and nitrogen rather than water, experience density driven stratification, forming layers similar to lakes on Earth. However, whereas lakes on Earth stratify in response to temperature, Titan’s lakes stratify solely due to the strange chemical interactions between its surface liquids and atmosphere, says a paper by Planetary Science Institute Research Scientist Jordan Steckloff.

Stratification occurs when different parts of a lake have different densities, with the less dense layer floating atop the denser layer. On Earth, lakes in temperate climates often stratify into layers in the summer as the Sun heats the surface of the lake, causing this water to expand and become less dense, forming a layer of warm water that literally floats upon the cooler water below. This density-driven stratification can occur on Titan as well; however it happens due to the amount of atmospheric nitrogen that Titan’s surface liquids can dissolve, rather than the liquids warming up and expanding.

…Because liquid methane is less dense than liquid ethane, it has been long assumed that Titan’s methane would generally float atop its liquid ethane. However, when methane’s affinity for atmospheric nitrogen is accounted for, methane can dissolve sufficient nitrogen at low temperatures to become denser than ethane.

This result has a great deal of uncertainty, mostly because of the relatively small dataset available of Titan. What it really shows is the possibility of this phenomenon. To confirm it will require some in situ measurements.

Using data collected by Cassini while it orbited Saturn for thirteen years, scientists have found that there might be more relatively fresh ice on the surface of the moon Enceladus than previously believed.

Cassini scientists discovered in 2005 that Enceladus – which looks like a highly reflective, bright white snowball to the naked eye – shoots out enormous plumes of ice grains and vapor from an ocean that lies under the icy crust. The new spectral map shows that infrared signals clearly correlate with that geologic activity, which is easily seen at the south pole. That’s where the so-called “tiger stripe” gashes blast ice and vapor from the interior ocean.

But some of the same infrared features also appear in the northern hemisphere. That tells scientists not only that the northern area is covered with fresh ice but that the same kind of geologic activity – a resurfacing of the landscape – has occurred in both hemispheres. The resurfacing in the north may be due either to icy jets or to a more gradual movement of ice through fractures in the crust, from the subsurface ocean to the surface.

The image above, cropped, reduced, and rearranged to post here, shows two views of Enceladus. On the left we are looking at one hemisphere, with the south pole at the bottom. On the right we are looking straight down at the south pole. The red areas are where scientists think there is relatively fresh ice. While the new ice is very pronounced at the south pole, where the tiger-striped vents have been found, the northern ice is much less evident, though clearly there.

That northern fresh ice however might not come from the planet’s interior, as suggested by the press release. It might also be new ice deposited from space that came from those very active tiger stripes. At the present time the data doesn’t allow for any solid conclusions.

Volcano-like features seen in polar regions of Saturn’s moon Titan by NASA’s Cassini spacecraft could be evidence of explosive eruptions that may continue today, according to a new paper by Planetary Science Institute Senior Scientist Charles A. Wood and coauthor Jani Radebaugh of Brigham Young University.

Morphological features such as nested collapses, elevated ramparts, halos, and islands indicate that some of the abundant small depressions in the north polar region of Titan are volcanic collapse craters, according to “Morphologic Evidence for Volcanic Craters near Titan’s North Polar Region” that appears in the Journal of Geophysical Research: Planets. A few similar depressions occur near the south pole of Titan. “The close association of the proposed volcanic craters with polar lakes is consistent with a volcanic origin through explosive eruptions followed by collapse, as either maars or calderas,” Wood said. “The apparent freshness of some craters may mean that volcanism has been relatively recently active on Titan or even continues today.”

The data being somewhat think, there is a great deal of uncertainty with this theory. Nonetheless, it makes perfect sense, and in fact it would be a surprise if some sort of volcanic activity was not occurring on Titan.

Planetary scientists today released the first global geologic map of the Saturn moon Titan. The image on the right is a reduced version of the full image.

In the annotated figure, the map is labeled with several of the named surface features. Also located is the landing site of the European Space Agency’s (ESA) Huygens Probe, part of NASA’s Cassini mission.

The map legend colors represent the broad types of geologic units found on Titan: plains (broad, relatively flat regions), labyrinth (tectonically disrupted regions often containing fluvial channels), hummocky (hilly, with some mountains), dunes (mostly linear dunes, produced by winds in Titan’s atmosphere), craters (formed by impacts) and lakes (regions now or previously filled with liquid methane or ethane).

To put it mildly, there is a lot of uncertainty here. Nonetheless, this is a first attempt, and it shows us that the distribution of these features is not homogeneous. The dunes favor the equatorial regions, the lakes the polar regions. Also, the small number of craters could be a feature of erosion processes from the planet’s active atmosphere, or simply be because Cassini’s radar data did not have the resolution to see smaller craters. I suspect the former.

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.

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.

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.

Click for original raw image.

The black box in the approach image to the right indicates the location of the close-up below. It covers a region dubbed Padua Chasmata, named for the white lined features running north-south near its center and separating the heavily cratered terrain to the east and the smoother plains to the west.

To help you understand the Cassini image, note that the spacecraft was approaching from the east, so that the approach image looks west. You can see Padua Chasmata cutting diagonally across the photograph. The giant shallow crater to the east of the chasmata is clearly visible on the global map above.

The black box indicates the location of one of 20 close-up images taken during that fly-by, and which I have posted below and to the right.

Click for full resolution image.

The photograph was taken from about 2,787 miles, with a resolution of 75 feet per pixel.

The Cassini science team gave this image a press release, noting;

The terrain in this image is located within a 60-kilometer-wide (37-mile) impact crater along the feature called Padua Linea. The western rim of the encompassing crater runs from the middle left to the upper right. The crater’s central peak can be seen at the lower right.

Multiple generations of fractures are visible here. Numerous fine, roughly parallel linear grooves run across the terrain from top to bottom and are interrupted by the larger, irregular bright fractures. In several places, fractures postdate some deposits in the bottoms of craters that are not badly degraded by time. Such a fracture, for example, runs from the center toward the upper right.

Most of the craters seen here have bright walls and dark deposits of material on their floors. As on other Saturnian moons, rockslides on Dione may reveal cleaner ice, while the darker materials accumulate in areas of lower topography and lower slope (e.g. crater floors and the bases of scarps).

This close-up photograph showed that the white lines of Padua Chasmata were both cliffs and fractures. Also, note now the largest white cliff near the top slight to the right of center appears to be the wall of a small crater, as if that impact had sliced down the side of the larger crater rim wall as it came in.

The make-up of these cliffs and fractures is only vaguely known. We know even less of the geological processes going on here, though scientists of course have made some educated guesses.

While Cassini did a number of additional close flybys of Dione in the next dozen years, none was ever as close. Cassini is now gone, so we shall not get a better view of this terrain until a new mission arrives, something that is likely not to occur for many decades. At the moment the only mission planned for Saturn, Dragonfly, is going to head to the moon Titan. At the moment it does not look like the mission will include a Saturn orbiter.

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.