Archive for February, 2011

Saturn posts

Saturn is an impressive planet, even though it’s not quite the grandiosity of Jupiter. The extensive and bright ice rings surrounding the planet make it an object of fascination for many people. Although Jupiter has some ring activity going on, Saturn has more. It is very interesting to know that we may be seeing the rings of Saturn at a particularly bright period and that they will wane over the next several million years. It is a bit mind-blowing to think about how short and yet how long a time-span these rings are particularly bright due to impacts with Saturn’s icy moons. We are lucky, in a sense, to exist in this time so as to see the rings in a bright state.

That Saturn has Titan as its moon is also of intense interest. Titan seems to be another possibility for finding life outside of Earth in our solar system. The fact that it has such a dense atmosphere and liquid (even if it’s not water)on its surface is exciting. Its weather patterns which are similar to those on Earth also add to the excitement. I hope that we are able to find out a whole lot more about this planet-like moon in my lifetime.

As for Holst’s music regarding Saturn: It starts out so slowly and quietly that it almost seems ominous—like something is creeping forward. It doesn’t seem to pick up much at all until the slow growth in dynamics which begins about half-way through the piece. This gradual increase in volume and intensity doesn’t reach its climax for a couple minutes after it begins; it plods along like an elephant walks.In fact, the pace is relatively slow and steady all the way through. I could almost describe the feeling of the piece as vaguely sinister, but I’m a on the fence on that. I’m not convinced of it being sinister, but it is definitely eerie. It reminds me of the hands of time marching forward wearily and slowly, which is appropriate if Saturn is the bringer of old age. The part at the end after the momentary break in music does sound a lot more hopeful and bright. It’s lovely, really. I can envision new life—as if the piece goes from old age into new life.


NASA update Cassini

NASA’s Cassini spacecraft has successfully completed its closest flyby of Saturn’s moon Rhea, returning raw images of the icy moon’s surface.

Pictures of the Rhea surface taken around the time of closest approach at 4:53 a.m. UTC on Jan. 11, 2011, which was 8:53 p.m. PST, Jan. 10, show shadowy craters at a low sun angle. A portrait of bright, icy Rhea also captures Saturn’s rings and three other moons clearly visible in the background.

Images obtained by Cassini’s imaging science subsystem show an old, inert surface saturated with craters, just like the oldest parts of Earth’s moon. But there appear to be some straight faults that were formed early in Rhea’s history, which never developed the full-blown activity seen on another of Saturn’s moons, Enceladus.

The flyby of Rhea also presented scientists with their best available chance to study how often tiny meteoroids bombard the moon’s surface. Scientists are now sifting through data collected on the close flyby by the cosmic dust analyzer and the radio and plasma wave science instrument. They will use the data to deduce how often objects outside the Saturn system contaminate Saturn’s rings, and to improve estimates of how old the rings are.

Scientists using Cassini’s fields and particles instruments are also looking through their data to see if they learned more about Rhea’s very thin oxygen-and-carbon-dioxide atmosphere and the interaction between Rhea and the particles within Saturn’s magnetosphere, the magnetic bubble around the planet.

At closest approach, Cassini passed within about 69 kilometers (43 miles) of the surface.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.

For more information about the Cassini-Huygens mission, visit and .

Media contact:
Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.


Surprise Hidden in Titan’s Smog: Cirrus-Like Clouds

Saturn and Titan Titan, the largest of Saturn’s moons, is about to slip behind the planet in this portrait captured by the Cassini spacecraft in 2008. Credit: NASA’s Jet Propulsion Laboratory

Titan seen behind Saturn's rings The blurring effects of Titan’s aerosol are obvious in this image, where the orange moon peeks from behind two of Saturn’s rings. Small, battered Epimetheus, another of Saturn’s 62 moons, appears just above the rings. Credit: NASA/JPL/Space Science Institute
› Larger image

Titan Titan’s northern half, where it’s early spring, appears slightly darker than the southern half, where it’s early fall, in this image taken on March 22, 2010. Like Earth, Titan has four distinct seasons, each of which lasts about seven of Earth’s years. Credit: NASA/JPL/Space Science Institute
› Larger image Every day is a bad-air day on Saturn’s largest moon, Titan. Blanketed by haze far worse than any smog belched out in Los Angeles, Beijing or even Sherlock Holmes’s London, the moon looks like a dirty orange ball. Described once as crude oil without the sulfur, the haze is made of tiny droplets of hydrocarbons with other, more noxious chemicals mixed in. Gunk.

Icky as it may sound, Titan is really the rarest of gems: the only moon in our solar system with an atmosphere worthy of a planet. This atmosphere comes complete with lightning, drizzle and occasionally a big, summer-downpour style of cloud made of methane or ethane — hydrocarbons that are best known for their role in natural gas.

Now, thin, wispy clouds of ice particles, similar to Earth’s cirrus clouds, are being reported by Carrie Anderson and Robert Samuelson at NASA’s Goddard Space Flight Center in Greenbelt, Md. The findings, published February 1 in Icarus, were made using the Composite Infrared Spectrometer (CIRS) on NASA’s Cassini spacecraft.

Unlike Titan’s brownish haze, the ice clouds have the pearly white appearance of freshly fallen snow. Their existence is the latest clue to the workings of Titan’s intriguing atmosphere and its one-way “cycle” that delivers hydrocarbons and other organic compounds to the ground as precipitation. Those compounds don’t evaporate to replenish the atmosphere, but somehow the supply has not run out (yet?).

“This is the first time we have been able to get details about these clouds,” says Samuelson, an emeritus scientist at Goddard and the co-author of the paper. “Previously, we had a lot of information about the gases in Titan’s atmosphere but not much about the [high-altitude] clouds.”

Puffy methane and ethane clouds had been found before by ground-based observers and in images taken by Cassini’s imaging science subsystem and visual and infrared mapping spectrometer. Compared to those clouds, these are much thinner and located higher in the atmosphere. “They are very tenuous and very easy to miss,” says Anderson, the paper’s lead author. “The only earlier hints that they existed were faint glimpses that NASA’s Voyager 1 spacecraft caught as it flew by Titan in 1980.”

Out on a Limb

Even before Voyager 1 reached Titan, scientists knew the moon was wrapped in a thick atmosphere that probably contained hydrocarbons. Part of that atmosphere, Voyager found, is a haze so smothering that it hides every bit of the moon’s surface.

Only a small amount of visible light penetrates this haze, or aerosol, so studies rely on instruments that operate at wavelengths beyond human sight. This is how Voyager learned that Titan’s atmosphere is made mostly of nitrogen, as is Earth’s. Unlike Earth’s atmosphere, though, Titan’s has neither oxygen nor water to speak of. Instead, it contains small amounts of organic materials, including members of the hydrocarbon family such as methane, ethane and propane.

Voyager also picked up indications that Titan’s stratosphere, the second-lowest layer of its atmosphere, harbored “ices made from some exotic organic compounds,” Samuelson says. “At the time, that was about all we could tell.”

Fast-forward a quarter-century to mid-2006, past decades of research conducted from telescopes, past Cassini’s arrival at Saturn, past the European Space Agency’s Huygens probe landing on Titan and taking the first pictures of the surface, past the discovery of the methane and ethane clouds. At this point, Cassini continues to orbit Saturn and visit Titan and other moons periodically.

More than a half-dozen hydrocarbons have been identified in gas form in Titan’s atmosphere, but many more probably lurk there. Researchers worldwide are looking for them, including Anderson and Samuelson, who are using the CIRS (pronounced “sears”) instrument on Cassini.

Pinpointing the altitudes where such gases turn into ices is painstaking work. The researchers scan up and down the atmosphere, pausing at each altitude to catalog a slew of signals that have to be teased apart later so that the molecules can be identified. “You can learn a lot about a compound, even if you have no idea what it is, by looking at how it is distributed vertically,” says Anderson. “Where does it accumulate? Where does it dissipate? How thick is the boundary? Is there layering going on?”

Anderson and Samuelson start a series of observations near Titan’s north pole, at roughly the same latitudes Voyager looked at, 62 °N and 70 °N. On Earth, these would fall just inside and outside the ring for the Arctic Circle.

The team focuses on the observations made when CIRS is positioned to peer into the atmosphere at an angle, grazing the edge of Titan. This path through the atmosphere is longer than the one when the spacecraft looks straight down at the surface. Planetary scientists call this “viewing on the limb,” and it raises the odds of encountering enough molecules of interest to yield a strong signal.

It works. When the researchers comb through their data, they succeed in separating the telltale signatures of ice clouds from the aerosol. “These beautiful, beautiful ice clouds are optically thin, and they’re diffuse,” says Anderson. “But we were able to pick up on them because of the long path lengths of the observations.”

In addition to spotting the clouds, the researchers gather enough information to measure the sizes of the ice particles. The results get reported in a January 2010 Icarus paper by Anderson, Samuelson, their Goddard colleague Gordon Bjoraker and Richard Achterberg, a University of Maryland staff member working at Goddard.

“That was convincing evidence,” Anderson says. “What Voyager had seen was real.”

That Sinking Feeling

Clouds on Titan can’t be made from water because of the planet’s extreme cold. “If Titan has any water on the surface, it would be solid as a rock,” says Goddard’s Michael Flasar, the Principal Investigator for CIRS.

Instead, the key player is methane. The action starts high in the atmosphere, where some of the methane gets broken up and reforms into ethane and other hydrocarbons, or combines with nitrogen to make materials called nitriles. Any of these compounds can probably form clouds if enough accumulates in a sufficiently cold area.

The cloud-forming temperatures occur in the “cold, cold depths of Titan’s stratosphere,” says Anderson. Researchers think that the compounds get moved downward by a constant stream of gas flowing from the pole in the warmer hemisphere to the pole in the colder hemisphere. There, the gas sinks.

This circulation pattern steals so much gas from the warmer hemisphere that researchers can measure the imbalance. The influx of all this gas gives the colder hemisphere more clouds. “At colder temperatures, more gas will condense anyway,” Anderson explains, “and on top of that, the atmosphere dumps a whole bunch of extra gas there.”

She and Samuelson think this is why the ice clouds were first spotted in the north. When Voyager flew by in November 1980, the north had just crossed from winter into spring. And the north was in mid-winter when the team conducted their early observations. (One Titan year lasts 29-1/2 Earth years, so spring came again to Titan’s north in August 2009.)

Still, the team figured, the south shouldn’t lack ice clouds; it should just have fewer of them. “For 30 years, Bob [Samuelson] had been saying that these clouds should exist in the southern hemisphere,” says Anderson, “so we decided to look.”

The team checked Titan’s southern hemisphere (at 58 °S latitude) and both sides of the equator (15 °N and 15 °S). Sure enough, they spotted clouds in all three locations. And as predicted, the clouds in the north were more plentiful — in fact, three times more plentiful — than those just south of the equator.

“The fact that the clouds are more enhanced at the cold polar region is a promising sign,” says Flasar. “It strengthens this idea that the molecules making up these clouds are being carried downward by this global circulation.”

Exotic Ices

Part of Titan’s allure has long been the organic compounds in the atmosphere, especially because some are thought to be involved in the events that led to life on Earth. One of those is cyanoacetylene, a member of the nitrile family. The compound’s distinctive signature made it the first to be picked up in the northern ice clouds by Voyager 1 and by Anderson and Samuelson.

To make a connection between these molecules and life isn’t the point for Anderson, though. “I just love ices and aerosols,” she says, “and Titan is this great natural laboratory for studying them.”

As the researchers continue to identify compounds in Titan’s atmosphere, the next likely candidate for an ice is hydrogen cyanide, a nitrile with an earthly reputation as a poison. In the aerosol, the team is investigating an intriguing feature in the data that seems to represent larger hydrocarbons than anybody has identified before, according to Samuelson. Early clues suggest the signature could indicate polycyclic aromatic hydrocarbons (PAHs), which typically get noticed on Earth as pollutants released by the burning of fossil fuels. In space, PAHs form in the regions where stars are born and die.

Each nugget of information like this is helping scientists piece together the life cycle and ultimate fate of Titan’s hydrocarbons, which never reenter the atmosphere via evaporation. “They fall to the surface, and it’s a dead end,” says Samuelson, “and yet Titan’s atmosphere still has methane in it. We are trying to find out why.”

The Great Switcheroo

At first, Titan’s frozen nitriles seem entirely unrelated to Earth clouds. Even putting aside their exotic ingredients, they form much higher in the atmosphere: at altitudes of about 30 to 60 miles (in the stratosphere) versus no more than 11 miles (in the troposphere) for nearly all Earth clouds.

But Earth does have a few polar stratospheric clouds that appear over Antarctica (and sometimes in the Arctic) during winter. These clouds form in the exceptionally cold air that gets trapped in the center of the polar vortex, a fierce wind that whips around the pole high in the stratosphere. This is the same region where Earth’s ozone hole is found.

Titan has its own polar vortex and may even have a counterpart to our ozone hole. The degree of similarity is intriguing, says Flasar, given the different compositions and chemistries of the stratospheric clouds on Earth versus Titan.

“We are starting to find out how similar Titan’s clouds are to Earth’s,” says Samuelson. “How do they compare? How do they not compare?”

The big test of scientists’ understanding of Titan’s atmosphere will come in 2017, when summer comes to the north and the south plunges into winter. “We expect to find a complete reversal in the circulation of gas then,” says Anderson. “The gas should start to flow from the north to the south. And that should mean most of the high-altitude ice clouds will be in the southern hemisphere.”

Other major changes are in store for Titan then, Flasar adds, including the disappearance of the fierce winds around the north pole. “The big question is: will the vortex go out with a bang or whimper?” he says. “On Earth, it goes out with a bang. It’s very dramatic. But on Titan, maybe the vortex just gradually fizzles out like the smile of the Chesire cat.”

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The CIRS team is based at NASA’s Goddard Space Flight Center in Greenbelt, Md., where the instrument was built.

Carl Sagon Saturn





Saturn Aurora


Jupiter Posts

Week 7 Reflection: Jupiter

Holst’s movement Jupiter might be the most famous of the suite’s pieces next to Mars. While not used as frequently in science-fiction films, it is the movement most often played by itself on the radio or in a performance. And it is no wonder – the piece is memorable, with a strong, repeated melody and variations on it supported, rather than contested, by the accompanying instruments. In this way, the structure of the song is more like a pop or vocal song, with a main voice performing the melody and the rest of the instrumentation providing the background.

However, Holst does something in this movement different from the majority of music with a strong melodic line: he gives the melody to the bass instruments. The theme is first introduced by the brass, namely the tubas, trombones, and euphoniums, echoed briefly by the bright trumpets before bouncing back to the lower brass. Again and again, any new section of the melody or variation on it is first played by the low instruments, and only echoed by the higher instruments – the clarinets, flutes, trumpets, oboes, etc… – which the rest of the time are relegated to providing a scintillating background. This conveys the effect of the mass, weight, and sheer gargantuan proportions of the largest planet in the system.

The melody itself is audacious and jovial… except for the middle section. Here the melody shift to the mid-tone instruments – french horns, lower strings, and the lower registers of the clarinets – and takes on a slower, steadier, reflective tone, like someone thinking of happy, by-gone days. In fact, the conductor in the video has to make an exaggerated face to remind the players this section is supposed to be happy too as the emotion of the section almost slips into a melancholic nostalgia. Besides simply providing contrast, it’s difficult to imagine what the purpose of the middle section is suppose to be. Wistfulness doesn’t quite seem to fit the personality of the god of joy.

The sheer size of sound in the piece is absolutely evocative of the size of Jupiter – it is 11 times the diameter of Earth and almost 318 times its mass. There the similarities end, however. Jupiter is an inhospitable planet. The composition is mostly hydrogen and helium, similar to the sun, mostly in liquid form because of the intense atmospheric pressure. This liquid hydrogen forms the largest ocean in the solar system. The atmosphere itself, though, is incredibly only 1% of the planet’s radius. The entire “surface” of the planet that can be seen through a telescope is actually clouds, rotating around the planet in belts of high, bright gasses and lower clouds which reflect back less light, therefore appearing darker. While we can’t get an instrument down far enough to tell what the temperature is deeper than 130km, the core itself is estimated to be five times hotter than the surface of the sun. Jupiter also has 63 confirmed moons by the latest count! Its sheer mass is able to hold these numerous satellites in orbit. There is a possibility that on some of the moons, such as Europa, which have evidence of significant amounts of water, there might be life. Eight of these moons are large enough that if they orbited the sun instead, they would be considered dwarf planets. Jupiter is almost a solar system within a solar system. Given today’s knowledge, if The Planets were rewritten, it might be more suitable to evoke Jupiter the King and Jupiter the Father, rather than Jupiter the Jovial.


CHID 496

14 February 2011


I find Jupiter to be the most interesting planet we have studied so far.  The planet is different from any of the terrestrial worlds in almost every respect.  Possessing a mass and size difficult to conceptualize, Jupiter is the center of its own miniature solar system.  The planet is extremely colorful, unlike the monotone visages of Mars, Venus, and Mercury.  The planet has no identifiable surface.  All of the gas giants are of a similar type, but looking first at Jupiter, the grandest gas giant, creates a large contrast between the gas planets and the rocky worlds.

Listening to Holst’s music, the brass section sounds something like a fanfare until 1:03 where the actual melody begins.  Jupiter, the king of the gods is the namesake of the king of the planets, so this amount of introduction makes a great deal of sense.

Holst characterizes Jupiter as the bringer of jollity.  Thus I would expect the piece to be full of exuberant energy and an almost drunken happiness.  But it nowhere attains this reveling attitude.  Instead, much of the piece maintains a measure of dignity as the melody marches on.  The movement in the melody suggests purpose and direction; the music is inspiring.  I find all this to be an appropriate characterization of creator king of gods.  I am not sure what Holst means by jollity.  The music is too serious in parts, such as 3:40, to be considered happy.  Perhaps Holst refers to the feelings brought on by hope and self-confidence.

Either way, I am glad that the music’s emotional content is multi-dimensional.  Mars was almost entirely a nerve-wracking war march, and Venus never once left its peaceful demeanor.  But Jupiter is not always blasting majestic tones.  Consider the quietness of 2:50 and the use of a tambourine at 6:30.  These sections seem slightly outside of the unassailable dignity of royalty which seems to pervade other sections of the peace.  This fits the god Jupiter, who was anything but constant.  There are times when Jupiter is the role-model and mediator, but also Jupiter is a womanizer.  Sometimes too, Jupiter is wrathful.

With Venus and Mercury, I have remarked upon the disparity between the music and the physical counterparts.  However, with Jupiter, I think Holst is right on point.  If anything, Jupiter is awe-inspiring, and the music captures that.  I think of Jupiter with an amount of reverence and wonder.  I think it will be a long time before humans are so familiar with the planet and its workings that Holst’s grand rendition seems out of place.


Weekly Response #4




I like the idea that Jupiter could have been a second sun to our solar system had things turned out a little differently. It is fascinating to me that with all of its moons, Jupiter is almost like a mini-solar system within our own solar system. The sheer size of Jupiter is pretty amazing, especially when the book shows the size of Earth right next to Jupiter. I, like I think a lot of people, am especially interested in Jupiter’s moons. I think it was the movie GATTACA which first interested me most in Jupiter’s moons—in the movie, the main character is set to go to Europa, if I’m not mistaken.

That this large Jovian planet is named after the Roman King of the Gods is appropriate given its sheer size and the dramatic effects it has on the rest of the solar system. That it affects meteors and asteroids and actually helps protect some of the inner planets from these stray bodies is rather like something you’d expect from the King of the Gods. Without Jupiter, Earth would not be what it is today.

The planet itself from where we can view it looks beautiful with the swirling gasses and the Great Red Spot. This is appropriate for the music of Holst’s. The music is both beautiful and wondrous. There is a feeling of definite joviality in this piece, which seems to reflect a regal ruler of the Gods. The usage of brass instruments in several portions of the piece also add to the idea of royalty being reflected in the music. I really enjoyed this composition. It is indeed very majestic and awe inspiring, just as it should be. I felt the movement of this piece and felt that it had purpose and direction. This is my favorite piece so far. The amount of variability in the music is great. It doesn’t get boring. Everything keeps moving and is optimistic and bright sounding.


Jupiter: Bringer of Jolly


It makes perfect sense that Jupiter was the king of the Roman Gods, given its massive size, strong magnetic field, and intimidating Great Red Spot.  Jupiter’s size is simply impossible for me to imagine, given that it is overwhelming to think about how big the Earth is (relative to me), and that the Great Red Spot alone is twice the diameter of Earth.  Given its daunting nature, it is difficult to connect Jupiter the feeling of being jolly.  Jupiter orbits rapidly, has an extremely hot core temperature, has more moons than any other planet, and even has a ring made up of microscopic particles, easily making it the ruler of the solar system, but not so easily invoking a sense jolliness.

Of all of the unique aspects of Jupiter, perhaps the most interesting are its four Galilean moons: Callisto, Ganymede, Europa, and Io.   Each moon has its own story and distinctive characteristics.  Callisto is a mixture of both ice and rock and while it has only a weak magnetic field of its own, it does interact with Jupiter’s magnetic field, suggesting that this moon actually has a layer of liquid water.  Ganymede is also a mixture of ice and rock, but it is mostly rock.  It has a mysterious magnetic field and relies on tidal heating for its heat source.  Europa is a mixture of rock and metal, with an icy surface that is almost completely free of craters, despite being closer to Jupiter than Ganymede.  It does not have a magnetic field, but the interaction from the magnetic field of Jupiter indicates that Europa has a liquid-water ocean that could contain twice as much water as all of the oceans on the Earth!  Io is the innermost moon, and yet does not have any impact craters on its surface due to its 150 plus active volcanoes.  There is no water on Io; instead it is mostly rock and sulfur.

While Jupiter itself does not seem very jolly, Gustav Holst’s movement for Jupiter certainly does.  It is upbeat and inviting, and even reminded me a bit of Christmas.  It is by far my favorite of all of the Planet songs so far.  The beginning and the end of the song reminded me of another song I had heard, but I could not quite figure out where I had heard it.  After listening to Holst’s music for about 30 minutes, it finally donned on me that I heard similar music in the chorus of a song from the first Shrek movie.  After another 30 minutes, I found this song on YouTube-it’s called It Is You (I Have Loved) by Dana Glover.  I then listened to this song for awhile before going back to Holst, and they indeed sounded very similar to me.  The piece by Holst is very symmetric, with the beginning and the end sounding almost identical, and the middle being a lot softer.




Jupiters Moons

Ring Moons

Metis, Adrastea, Amalthea,Thebe

Galilean Moons

Io, Eurpopa, Ganymede, Callisto

Additional Moons

Themisto, Leda, Himalia, Lysithea, Elara, S/2000J11, Carpo,S/2003J12,Euporie,J3,J18,Thelxinoe,Euanthe,Helike,Orthosie,Locaste,J16,Praxidike,Harpalyke,Mneme,Hermippe,Thyone,Ananke,Herse,Aitne,Kale,Taygete,J19,Chaldene,J15,J10,J23,Erinome,Aoede, Kallichjore,Kalyke,Carme,Callirrhoe,Eurydome,Pasithee,Kore,Cyllene,Eukelade,J4,Pasiphae,Hegemone,Arche,Isonoe, J9,J5,Sinope,Sponde,Autonoe,Megaclite,J2