Close-up view of Enceladus from Cassini's Aug. 11 flyby. Credit" NASA/JPL
Scientists for the Cassini mission called their flyby of Saturn’s small moon Enceladus on August 11 a “skeet shoot,” partially in honor of the current Olympic games underway, but mostly because the spacecraft would be trying to shoot rapidly at the moon with its array of cameras and scientific instruments. As the images begin to stream back, the scientists are definitely excited about what they’re seeing.
“What a dazzling success!” said Carolyn Porco, the Cassini Imaging Team Leader. “There doesn’t even appear to be any smear.” Scientists compared Cassini’s fast flyby of Enceladus to trying to capture a sharp, unsmeared picture of a roadside billboard about a mile away with a 2,000 mm telephoto lens held out the window of a car moving at 50 mph. The imaging team is still poring over the pictures to see if they were successful in “shooting” their target: the active vent regions on the tiger stripe-like features on the moon’s south pole that create the geysers on Enceladus. But the amazingly clear images show a fractured surface littered with boulders and what Porco said could possibly be ice blocks.
Cassini flew over the surface of Enceladus at tremendous speed; about 18 km/sec (about 40,000 mph), which makes taking clear images very difficult. The imaging team devised a technique of turning the spacecraft while taking pictures in rapid succession, shooting at seven, very high priority surface targets. The suite of images ranged in resolution from 8 to 28 meters/pixel, using exposure times that were long enough to see the surface in the twilight near the terminator yet short enough to avoid smear.
Overview of Cassini's flyby. Credit: NASA/JPL
The tiger stripes, officially called sulci, have been identified by the imaging cameras on earlier flybys of Enceladus as the sources of the jets, and also as the “hot spots” or warmer areas on the moon identified by the Cassini’s Composite Infrared Spectrograph.
Porco said the team still has much work to do to decipher all the information in the images and data from the other instruments. “In this painstaking work, we proceed, step by step, to lay bare those things which hold the greatest promise of comprehension, the greatest significance for piecing together the story of the origins of the bodies in our solar system, our Earth, and indeed ourselves,” she wrote in her blog.
We’ll provide further updates on the flyby images as information becomes available.
Rendering of a blue liquid metal... could this be what metallic helium looks like? Source: http://tinyurl.com/6lffol (waxellis)
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The interiors of the two gas giants, Jupiter and Saturn, are pretty extreme places. With atmospheric pressures of around 70 million Earth atmospheres, the phases of material become a bit difficult to understand. Usually when we think of a liquid metal, we have thoughts about liquid mercury at room temperature (or the reassembling liquid metal T-1000 played by Robert Patrick in the film Terminator 2), rarely do we consider two of the most abundant elements in the Universe to be a liquid metal in certain conditions. And yet, this is what a team of physicists from UC Berkley are claiming; helium and hydrogen can mix together, forced by the massive pressures near the cores of Jupiter and Saturn, forming a liquid metal alloy, possibly changing our perception of what lies beneath those Jovian storms…
Usually planetary physicists and chemists focus most of their attention on the characteristics of the most abundant element in the Universe: hydrogen. Indeed, over 90% of both Jupiter and Saturn is hydrogen too. But within these gas giant’s atmospheres is not the simple hydrogen atom, it is the surprisingly complex diatomic hydrogen gas (i.e. molecular hydrogen, H2). So, to understand the dynamics and nature of the insides of the most massive planets in our Solar System, researchers from UC Berkley and London are looking into a far simpler element; the second most abundant gas in the Universe: helium.
Raymond Jeanloz, a professor at UC Berkeley, and his team have uncovered an interesting characteristic of helium at the extreme pressures that can be exerted near the cores of Jupiter and Saturn. Helium will form a metallic liquid alloy when mixed with hydrogen. This state of matter was thought to be rare, but these new findings suggest liquid metal helium alloys may be more common than we previously thought.
“This is a breakthrough in terms of our understanding of materials, and that’s important because in order to understand the long-term evolution of planets, we need to know more about their properties deep down. The finding is also interesting from the point of view of understanding why materials are the way they are, and what determines their stability and their physical and chemical properties.” – Raymond Jeanloz.
Jupiter for example exerts an enormous pressure on the gases in its atmosphere. Due to it’s large mass, one can expect pressures up to 70 million Earth atmospheres (no, that isn’t enough to kick-start fusion…), creating core temperatures of between 10,000 to 20,000 K (that’s 2-4 times hotter than the Sun’s photosphere!). So helium was chosen as the element to study under these extreme conditions, a gas that makes up 5-10% of the Universe’s observable matter.
Using quantum mechanics to calculate the behaviour of helium under different extreme pressures and temperatures, the researchers found that helium will turn into a liquid metal at very high pressure. Usually, helium is thought of as a colourless and transparent gas. In Earth-atmosphere conditions this is true. However, it turns into an entirely different creature at 70 million Earth atmospheres. Rather than being an insulating gas, it turns into a conducting liquid metal substance, more like mercury, “only less reflective,” Jeanloz added.
This result comes as a surprise as it has always been thought that massive pressures make it more difficult for elements like hydrogen and helium to become metal-like. This is because the high temperatures in locations like Jupiter’s core cause increased vibrations in atoms, thus deflecting the paths of electrons trying to flow in the material. If there is no electron flow, the material becomes an insulator and cannot be called a “metal.”
However, these new findings suggest that atomic vibrations under these kinds of pressures actually have the counter-intuitive effect of creating new paths for the electrons to flow. Suddenly the liquid helium becomes conductive, meaning it is a metal.
In another twist, it is thought that the helium liquid metal could easily mix with hydrogen. Planetary physics tells us that this isn’t possible, hydrogen and helium separate like oil and water inside the gas giant bodies. But Jeanloz’s team has found that the two elements could actually mix, creating a liquid metal alloy. If this is to be the case, some serious re-thinking of planetary evolution needs to be done.
Both Jupiter and Saturn release more energy than the Sun provides meaning both planets are generating their own energy. The accepted mechanism for this is condensing helium droplets that fall from the planets’ upper atmospheres and to the core, releasing gravitational potential as the helium falls as “rain.” However, if this research is proven to be the case, the gas giant interior is likely to be a lot more homogenous than previously thought meaning there can be no helium droplets.
So the next task for Jeanloz and his team is to find an alternate power source generating heat in the cores of Jupiter and Saturn (so don’t go re-writing the textbooks quite yet…)
Artist concept of Cassini flying by Saturn's moon Enceladus. Image credit: NASA/JPL
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Saturn’s tiny moon Enceladus is of big interest to planetary scientists trying to understand the dynamics of the moon’s geysers and fissures. On August 11, the Cassini spacecraft will swoop by Enceladus for a close flyby, just 50 kilometers (30 miles) from the surface, with the fractures, or “tiger stripes” near the moon’s south pole, where icy jets erupt as the target of study for the Cassini instruments. “Our main goal is to get the most detailed images and remote sensing data ever of the geologically active features on Enceladus,” said Paul Helfenstein, a Cassini imaging team associate at Cornell University in Ithaca, NY. “From this data we may learn more about how eruptions, tectonics, and seismic activity alter the moon’s surface. We will get an unprecedented high-resolution view of the active area immediately following the closest approach.”
Cassini will actually try to see inside one of the fissures in high resolution, which may provide more information on the terrain and depth of the fissures, as well as the size and composition of the ice grains inside. Refined temperature data could help scientists determine if water, in vapor or liquid form, lies close to the surface and better refine their theories on what powers the jets.
Cassini discovered evidence for the geyser-like jets on Enceladus in 2005, finding that the continuous eruptions of ice water create a gigantic halo of ice and gas around Enceladus, which helps supply material to Saturn’s E-ring. Just after closest approach, all of the spacecraft’s cameras — covering infrared wavelengths, where temperatures are mapped, as well as visible light and ultraviolet — will focus on the fissures running along the moon’s south pole. That is where the jets of icy water vapor emanate and erupt hundreds of miles into space. The image resolution will be as fine as 7 meters per pixel (23 feet) and will cover known active spots on three of the prominent “tiger stripe” fractures.
This will be Cassini’s second flyby of Enceladus this year. During the last flyby in March, the spacecraft snatched up precious samples and tasted comet-like organics inside the little moon. Two more Enceladus flybys are coming up in October, and they may bring the spacecraft even closer to the moon. The Oct. 9 encounter is complimentary to the March one, which was optimized for sampling the plume. The Oct. 31 flyby is similar to this August one, and is again optimized for the optical remote sensing instruments.
The Cassini web page has a mission blog that will follow the fly by, and you can also find images and videos as well.
Project Lucifer. Could the plutonium fuel onboard the Cassini mission cause a nuclear chain reaction on Saturn? Credit: NASA
[/caption] The story: The Lucifer Project is allegedly the biggest conspiracy theory NASA could possibly be involved in. First, back in 2003, the space agency (in co-operation with secret and powerful organizations) dropped the Galileo probe deep into Jupiter’s atmosphere. On board, was a significant quantity of plutonium. As the probe fell though the atmosphere, NASA hoped atmospheric pressures would create an implosion, generating a nuclear explosion thereby kick-starting a chain reaction, turning the gas giant into a second Sun. They failed. So, in a second attempt, they will drop the Cassini probe (again, laden with plutonium) deep into Saturn’s atmosphere in two years time, so this smaller gas giant can succeed where Jupiter failed…
The reality: As investigated briefly in Project Lucifer: Will Cassini Turn Saturn into a Second Sun? (Part 1), we looked at some of the technical problems behind Galileo and Cassini being used as makeshift nuclear weapons. They cannot generate an explosion for many reasons, but the main points are: 1) Tiny pellets of plutonium used to heat and power the probes are in separate, damage-proof cylinders. 2) The plutonium is not weapon grade, meaning the 238Pu makes a very inefficient fissionable fuel. 3) The probes will burn up and break apart, therefore disallowing any chance of lumps of plutonium forming “critical mass” (besides, there is no chance the plutonium could possibly form a configuration to create an implosion-triggered device).
OK, so Galileo and Cassini cannot be used as crude nuclear weapons. But say if there was a nuclear explosion inside Saturn? Could it cause a chain reaction in the core, creating a second Sun?
Thermonuclear bombs The Soviet 50-megaton Tsar Bomba, the largest weapon ever detonated (1961)
Unless nuclear fusion can be maintained within a stellar body, the reaction will very quickly fizz out. So the Lucifer Project proposes Cassini will plunge many hundreds of miles into the atmosphere of Saturn and explode as a crude plutonium-fuelled fission explosion. This explosion will cause a chain reaction, creating enough energy to trigger nuclear fusion inside the gas giant.
I can see where this idea has come from, even though it is inaccurate. The fusion bomb (or “thermonuclear weapon”) uses a fission trigger to kick-start an uncontrolled fusion reaction. The fission trigger is constructed to explode like a normal fission bomb much like the implosion device described in Part 1 of this series. When detonated, huge quantities of energetic X-rays are produced, heating the material surrounding the fusion fuel (such as lithium deuteride), causing the phase transition to a plasma. As very hot plasma is surrounding the lithium deuteride (in a very confined and pressured environment) the fuel will produce tritium, a heavy hydrogen isotope. Tritium then undergoes nuclear fusion, liberating huge quantities of energy as the tritium nuclei are forced together, overcoming the electrostatic forces between nuclei and fusing. Fusion releases large quantities of binding energy, more-so than fission.
How does a star work? A comparison of the size of Jupiter, a brown dwarf, a small star and the Sun (Gemini Observatory/Artwork by Jon Lomberg)
The point that needs to be emphasised here is that in a thermonuclear device, fusion can only be attained when immense temperatures are reached within a very confined and pressurized environment. What’s more, in the case of a fusion bomb, this reaction is uncontrolled.
So, how are nuclear fusion reactions sustained in a star (like our Sun)? In the thermonuclear bomb example above, tritium fusion is achieved through inertial confinement (i.e. rapid, hot and energetic pressure on the fuel to cause fusion), but in the case of a star, a sustained mode of confinement is required. Gravitational confinement is needed for nuclear fusion reactions to occur in the core. For significant gravitational confinement, the star requires a minimum mass.
In the core of our Sun (and most other stars smaller than our Sun), nuclear fusion is achieved through the proton-proton chain (pictured below). This is a hydrogen burning mechanism where helium is generated. Two protons (hydrogen nuclei) combine after overcoming the highly repulsive electrostatic force. This can only be achieved if the stellar body has a large enough mass, increasing gravitational containment in the core. Once the protons combine, they form deuterium (2D), producing a positron (quickly annihilating with an electron) and a neutrino. The deuterium nucleus can then combine with another proton, thus creating a light helium isotope (3He). The outcome of this reaction generates gamma-rays that maintain the stability and high temperature of the star’s core (in the case of the Sun, the core reaches a temperature of 15 million Kelvin).
The proton-proton chain that fuels nuclear fusion inside the core of our Sun. Credit: Ian O'Neill
As discussed in a previous Universe Today article, there are a range of planetary bodies below the threshold of becoming a “star” (and not able to sustain proton-proton fusion). The bridge between the largest planets (i.e. gas giants, like Jupiter and Saturn) and the smallest stars are known as brown dwarfs. Brown dwarfs are less than 0.08 solar masses and nuclear fusion reactions have never taken hold (although larger brown dwarfs may have had a short period of hydrogen fusion in their cores). Their cores have a pressure of 105 million atmospheres with temperatures below 3 million Kelvin. Keep in mind, even the smallest brown dwarfs are approximately 10 times more massive than Jupiter (the largest brown dwarfs are around 80 times the mass of Jupiter). So, for even a small chance of the proton-proton chain occurring, we’d need a large brown dwarf, at least 80 times bigger than Jupiter (over 240 Saturn masses) to even stand the hope of sustaining gravitational confinement.
There’s no chance Saturn could sustain nuclear fusion? Saturn, seen by Cassini. Image credit: NASA/JPL/SSI
Sorry, no. Saturn is simply too small.
Implying that a nuclear (fission) bomb detonating inside Saturn could create the conditions for a nuclear fusion chain reaction (like the proton-proton chain) is, again, in the realms of science fiction. Even the larger gas giant Jupiter is far too puny to sustain fusion.
I have also seen arguments claiming that Saturn consists of the same gases as our Sun (i.e. hydrogen and helium), so a runaway chain reaction is possible, all that is needed is a rapid injection of energy. However, the hydrogen that can be found in Saturn’s atmosphere is diatomic molecular hydrogen (H2), not the free hydrogen nuclei (high energy protons) as found in the Sun’s core. And yes, H2 is highly flammable (after all it was responsible for the infamous Hindenburg airship disaster in 1937), but only when mixed with a large quantity of oxygen, chlorine or fluorine. Alas Saturn does not contain significant quantities of any of those gases.
Conclusion
Although fun, “The Lucifer Project” is the product of someone’s lively imagination. Part 1 of “Project Lucifer: Will Cassini Turn Saturn into a Second Sun?” introduced the conspiracy and focused on some of the general aspects why the Galileo probe in 2003 simply burned up in Jupiter’s atmosphere, scattering the small pellets of plutonium-238 as it did so. The “black spot” as discovered the next month was simply one of the many dynamic and short-lived storms often seen to develop on the planet.
This article has gone one step further and ignored the fact that it was impossible for Cassini to become an interplanetary atomic weapon. What if there was a nuclear explosion inside Saturn’s atmosphere? Well, it looks like it would be a pretty boring affair. I dare say a few lively electrical storms might be generated, but we wouldn’t see much from Earth. As for anything more sinister happening, it is highly unlikely there would be any lasting damage to the planet. There would certainly be no fusion reaction as Saturn is too small and it contains all the wrong gases.
Oh well, Saturn will just have to stay the way it is, rings and all. When Cassini completes its mission in two years time, we can look forward to the science we will accumulate from such an incredible and historic endeavour rather than fearing the impossible…
Update (Aug. 7th): As pointed out by some readers below, molecular hydrogen wasn’t really the cause of the Hindenburg airship disaster, it was the aluminium-based paint that may have sparked the explosion, hydrogen and oxygen fuelled the fire.
Project Lucifer. Could the plutonium fuel onboard the Cassini mission cause a nuclear chain reaction on Saturn? Credit: NASA/US Department of Defense
[/caption] The story: On October 15th 1997, the Cassini-Huygens mission blasted off from Cape Canaveral Air Force Station to explore Saturn and its moons. It continues to study the ringed gas giant today and its mission has been extended till 2010. Cassini is is powered by 32.8 kg (72 lbs) of plutonium fuel. A radioactive power source is the only option for missions travelling beyond the orbit of Mars as sunlight is too weak for solar panels to be effective. However, NASA (in association with secret organizations, such as the Illuminati or the Freemasons) wants to use this plutonium for a “higher purpose”, dropping Cassini deep into Saturn at the end of its mission where atmospheric pressures will be so large that it will compress the probe, detonating like a nuclear bomb. What’s more, this will trigger a chain reaction, kick-starting nuclear fusion, turning Saturn into a fireball. This is what has become known as The Lucifer Project. This second sun will have dire consequences for us on Earth, killing millions from the huge influx of radiation by this newborn star. Earth’s loss becomes the Saturn moon Titan’s gain, suddenly it is habitable and the organizations playing “God” can start a new civilization in the Saturn system. What’s more, exactly the same thing was attempted when the Galileo probe was dropped into Jupiter’s atmosphere in 2003…
The reality: Now that the Cassini mission has been extended by two years, we can expect this conspiracy theory to become more and more vocal in the coming months. But like the Galileo/Jupiter/second sun theory, this one is just as inaccurate, once again using bad science to scare people (much like Planet X then)…
So what happened when Galileo dropped into Jupiter? Galileo undergoing preparations before launch in 1989. Credit: NASA
Well… nothing really.
In 2003, NASA took the prudent decision to terminate the hugely successful Galileo mission by using its last drops of propellent to push it at high speed into the gas giant. By doing so, this ensured the probe would burn up during re-entry, dispersing and burning any contaminants (such as terrestrial bacteria and the radioactive plutonium-238 fuel on board). The primary concern about letting Galileo sit in a graveyard orbit was that if mission control lost contact (very likely as the radiation belts surrounding Jupiter were degrading the probe’s ageing electronics), there may have been the possibility that Galileo would crash into one of the Jovian moons, contaminating them and killing any possible extra-terrestrial microbial life. This was a serious concern, especially in the case of Europa which could be a prime location for life to thrive below its ice-encrusted surface.
Now this is where the intrigue begins. Long before Galileo plummeted into Jupiter’s atmosphere, conspiracy theorists cited that NASA wanted to create an explosion within the body of the gas giant, thus igniting a chain reaction, creating a second sun (Jupiter is often called a ‘failed star’, although it has always been way too small to support nuclear reactions in its core). This was proven wrong on many counts, but there were three main reasons why this could not happen:
The design of the radioisotope thermoelectric generators (RTGs) supplying energy to the craft wouldn’t allow it.
The physics behind a nuclear explosion (nuclear fission) wouldn’t allow it.
The physics of how a star works (nuclear fusion) wouldn’t allow it.
Five years after the Galileo impact, Jupiter still looks to be in fine health (and it certainly isn’t close to being a star). Although history has already proven you can’t create a star from a gas giant using a space probe (i.e. Jupiter + Probe ≠ Star), conspiracy theorists think that NASA’s evil plan failed and there is some evidence that something did happen after Galileo got swallowed by Jupiter (and that NASA is pinning their hopes on the Cassini/Saturn combo).
Cue the Big Black Spot
The mystery black spot in 2003 (by Eric Ng) compared with one of the Shoemaker-Levy 9 fragments impact sites in 1994 (NASA)
Backing up the conspiracy theorists’ claims that there was an explosion inside the Jovian atmosphere after Galileo hit was the discovery of a dark blob near the equator of Jupiter a month after the event. This was widely reported across the web, but only a couple of observations were made before it disappeared. Some explanations pointed out that the blob could have been a short-lived dynamic atmospheric feature or it was a shadow from one of the Jovian moons. After this initial excitement, nothing else surfaced about the phenomenon. However, some were keen to point out that the dark patch on Jupiter’s surface may have been a manifestation of a nuclear detonation from Galileo deep within the planet which, after a month, eventually floated to the surface. Comparisons had even made with the 1994 features generated by the impact of the pieces of Comet Shoemaker-Levy 9 (pictured above).
What ever the cause of this dark feature, it didn’t come from Galileo as a nuclear detonation simply was not possible. What’s more, a nuclear detonation from the Cassini mission when it enters Saturn’s atmosphere in 2010 is also impossible, and here’s why…
The Radioisotope Thermoelectric Generators (RTGs) The Cassini RTG, one of three on board. Credit: NASA
RTGs are a tried and tested technology in use since the 1960’s. Various RTG designs have been used on a huge number of missions including Pioneer 10, Pioneer 11, Voyager 1, Voyager 2, Galileo, Ulysses, Cassini and, most recently, New Horizons. RTGs are a very dependable source of power for space missions where solar panels have not been an option. For Cassini, if solar panels were used, they would need to have a huge area to collect the meagre sunlight at 10 AU, thus impractical to launch and operate.
The three RTGs on board Cassini are fuelled by small pellets of plutonium-238 (238Pu) encased separately in shock-proof containers known as general purpose heat source modules. There are 18 modules in each RTG. Through the use of thermocouples, the steady heat generated by the radioactive decay of the plutonium isotope is converted into electricity to supply Cassini. It is worth noting at this point that 238Pu is not weapon grade (i.e. it is very difficult to generate nuclear fission, 239Pu is more suited for this purpose). There are also dozens of Radioisotope Heater Units (RHUs) on board Cassini that provide a steady heat to critical subsystems, which contain single pellets of Pu-238. Again, these units are separated and shielded, each weighing 40 grams. For more details on this, check out the NASA Factsheet: Spacecraft Power for Cassini.
Inside an RHU and RTG (Roland Piquepaille)
Shielding is critical for each plutonium pellet, primarily to prevent radioactive contamination during launch of space missions. Should there be an incident during launch, space agencies such as NASA must assure the containment of the radioactive material. Therefore all RTGs and RHUs are completely safe regardless of the stresses they are put under.
So, like Galileo, Cassini will hit Saturn’s atmosphere at a high velocity (Galileo hit the Jovian atmosphere at a speed of 50 km/s) and disintegrate very quickly before burning to a cinder. The point I want to highlight here is that Cassini will break apart like any fast-moving object during re-entry.
Still, conspiracy theorists are quick to point out that Cassini is carrying a huge amount of plutonium, totalling 32.8 kg (even though it is not the weapon-grade 239Pu and all the bits of 238Pu are tiny pellets, encased in damage-proof containers, being scattered through Saturn’s atmosphere). But ignoring all the logical arguments against, it will still generate a nuclear explosion, right?
Alas, no.
So how does a nuclear bomb work anyway?
Artist impression of Galileo burning up when falling into the Jovian atmosphere. Credit: David A Hardy
For a general run-down of the basics behind a nuclear weapon, check out the very clear description at How Stuff Works: How Nuclear Bombs Work (scroll down to “Implosion-Triggered Fission Bomb,” as this is what the conspiracy theorists believe Cassini will emulate).
So there’s Cassini, plummeting through Saturn’s atmosphere in two years time. As it gets deeper, bits fall off and burnt by the friction caused by re-entry. When I say fall off, I mean they are no longer attached. For a nuclear detonation to occur we need a solid mass of weapon grade plutonium. By solid mass, I mean we need a minimum amount of the stuff for nuclear fission to occur (a.k.a. “critical mass”). The critical mass of 238Pu is approximately 10 kg (US DoE publication), so Cassini has enough 238Pu for three crude nuclear bombs (ignoring the fact that it is very difficult to build a 238Pu weapon in the first place). But how could all those tiny pellets of 238Pu be pulled together, in free-fall, casings removed, letting the pressure of Saturn’s atmosphere force it all together tipping it toward critical mass? Is that really possible? No.
An imploding nuclear weapon (answers.com)
Even if by some chance all the 238Pu in one RTG melded together, how would it detonate? For detonation of an implosion-triggered fission bomb to occur, sub-critical masses need to be forced together at the same instant. The only way this is possible is to surround the sub-critical masses with high-explosives so a shock wave rapidly collapses the sub-critical masses together. Only then may a chain reaction be sustained. Unless NASA has been really sneaky and hidden some explosives inside their RTGs, detonation is not possible. Using atmospheric pressure alone is not a viable explanation.
Now we can see that it is pretty much impossible for the plutonium on board Cassini to create a nuclear explosion. But if there was a nuclear detonation, could a chain reaction occur? Could Saturn become a star?
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The answer to ”how far is Saturn from Earth” has a different answer every day. As the planets move along their orbital paths they move nearer and further in comparison to each other. For the sake of simplicity, Saturn is 1.2 billion km, roughly 7 AU, from the Earth when the two are at their closest approach to one another. They are 1.67 billion km, around 11 AU, from each other when they are at their most distant. Saturn and Earth are the closest to each other when they are on the same side of the Sun and at similar points in their orbits. The are the most distant when on opposite sides of the Sun.
Here are some of the other orbital and physical characteristics of Saturn compared to those of Earth.
Equatorial Diameter… 120,536 km, 9.44 times that of Earth
Polar Diameter… 108,728 km, 8.55 times that of Earth
Surface Area…4.27×1010 km2, 83.7 times that of Earth
Volume…8.2713×1014 km3, 763.6 times that of Earth
Mass…5.6846×1026 kg, 95.2 times that of Earth
Density… 0.687 g/cm3, one tenth that of Earth…Saturn could float in water.
Here are a few other interesting facts about Saturn that may interest you:
Saturn has 60 moons. That means that about 40% of the moons in our Solar System orbit around the planet. Many of these moons are very small and can not be seen from Earth. The last four were discovered by the Cassini spacecraft and scientist fully expect to find more as more spacecraft make their way toward Saturn.
Saturn is known for its amazing set of rings, but did you know that the occasionally disappear? Well, they disappear from our point of view anyway. The planet is tilted on its axis very similar to Earth. AS it makes its way along its 30 Earth year orbit of the Sun we sometimes see the rings full on and other time they are edge on from our perspective and disappear. This will next happen in 2024-2025.
While Saturn is too hostile for any form of life that we know, its moon Enceladus has ice geysers. That means that some mechanism is keeping the moon warm enough for liquid water to exist. As you know, here on Earth where ever there is liquid water there is life. Some scientist think that there is a chance for some type of life to exist on Enceladus.
Now that you know the answer to ”how far is Saturn from Earth”, we here at Universe Today hope that you will be inspired to find out more about the ringed planet.
An aurora dances on Saturn in this image from the Cassini orbiter. Credit: NASA/JPL/University of Arizona
Saturn’s gorgeous rings. Geysers on Enceladus. Methane lakes on Titan. These are just a few of the images that stand out from the Cassini mission’s four year survey of Saturn and its remarkable system of rings and moons. On June 30 the Cassini spacecraft completes its primary mission at the ringed planet, and now will embark on an extended two year mission, with hopes of studying more closely the most intriguing targets, Titan and Enceladus and the interaction between Saturn’s icy moons and rings.
“We’ve had a wonderful mission and a very eventful one in terms of the scientific discoveries we’ve made, and yet an uneventful one when it comes to the spacecraft behaving so well,” said Bob Mitchell, Cassini program manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We are incredibly proud to have completed all of the objectives we set out to accomplish when we launched. We answered old questions and raised quite a few new ones and so our journey continues.”
Mitchell said while its clear Cassini isn’t just driving off the showroom floor, considering how complex the nature of the mission has been and how long it’s been going, the spacecraft is doing remarkably well.
Cassini launched Oct. 15, 1997, taking seven years to traverse 3.5 billion kilometers (2.2 billion miles) to Saturn. The mission entered Saturn’s orbit on June 30, 2004, and began returning stunning data of Saturn’s rings almost immediately.
Mitchell said the spacecraft has made major discoveries about the dynamics of the rings, and how the moons gravity shapes the rings into the different gaps. “The geysers of Enceladus rank near the top of the excitement of the discoveries that we’ve made,†he said. “ Titan is very different than we expected it to be. It’s a lot like Earth, if you just replace water with methane there a lot of processes on Titan that look like Earth.â€
The extended mission will allow for monitoring seasonal effects on Titan and Saturn, exploring new places within Saturn’s magnetosphere, and observing the unique ring geometry of the Saturn equinox in August of 2009 when sunlight will pass directly through the plane of the rings.
The next two years, Cassini will have 26 more encounters with Titan, seven close encounters with Enceladus, and one each with the icy moons Dione, Rhea and Helene.
And there’s sure to be other discoveries at Saturn as well. “There are a number of surprises yet waiting for us, as the seasons change, we’re bound to find exciting things we haven’t even thought of yet,†said Mitchell.
Scientists from the Cassini mission are finding Saturn’s rings to be very dynamic; constantly changing and evolving. This is especially true for one of Saturn’s outermost rings, the F ring. This ring can change rapidly, sometimes on a timescale of hours, and astronomers believe it’s probably the only location in the solar system where large scale collisions happen on a daily basis. New images from the Cassini spacecraft have revealed unprecedented detail of this ring, including evidence that several small, unseen moons collide with other ring particles and cause perturbations called jets, streamers and fans.
Saturn’s F ring is very thin, just a few hundred kilometers wide, and is held together by two shepherd moons, Prometheus and Pandora, which orbit inside and outside the ring. For some time, scientists have suspected the presence of tiny moonlets that orbit Saturn in association with the clumpy F ring. As the small satellites move close to the F ring core they leave a gravitational signature. In some cases they can draw out material in the form of a “streamer.” Another perturbation called “jets” are the result of collisions between small nearby moonlets and the core of the F ring.
Scientists speculate that there could be several small moons with a variety of sizes that create these structures.
The leader of this analysis, Carl Murray of Queen Mary, University of London said, “Previous research has noted the features in the F ring and concluded that either another moon of radius about 100km must be present and scattering the particles in the ring, or a much smaller moonlet was colliding with its constituent particles. We can now say that the moonlet is the most likely explanation and even confirm the identity of one culprit.”
A ~5km object discovered by Cassini in 2004 (called S/2004 S 6) is the best candidate to explain some of the largest jets seen in the images.
The Cassini images also show new features called “fans” which result from the gravitational effect of small (~1km) satellites orbiting close to the F ring core.
Understanding these processes helps scientists understand the early stages of planet formation.
Professor Keith Mason, CEO of the Science and Technology Facilities Council which funds UK involvement in Cassini-Huygens said “This incredibly successful mission has taught us a great deal about the solar system and the processes at work in it. Understanding how small objects move within the dust rings around Saturn gives an insight into the processes that drive planetary formation, where the proto-planet collects material in its orbit through a dust plane and carves out similar grooves and tracks.”
Every year my car insurance company provides a free road atlas that helps me get where I need to go. Now, the imaging team from the Cassini spacecraft is ensuring that future travelers will be able to find their way around Saturn’s icy moons by providing detailed atlases of the surface features of these remote satellites. The Cassini Imaging Team just released the third in a series of atlases, this one charting the fractured, 1,125 kilometer-wide Dione. To do this, they stitched together 449 high resolution images of the moon to produce a global map. These atlases are being released simultaneously to the public and the scientific community, available with just a click or two of your mouse. So, get your free atlases here!
The atlases can be found at the CICLOPS website (Cassini Imaging Central Laboratory for Operations.) And while you’re getting your free atlas, browse around for other amazing (and free) images of the Saturn system, such as this sensational image of Enceladus backdropped with Saturn’s rings:
The Cassini imaging team previously released atlases of the geologically active Enceladus and the obscure outer moon Phoebe. Atlases of other moons will be released as Cassini’s mission continues, with Iapetus and Tethys next in line.
For Dione, the atlas was produced at a scale of 1:1,000,000, where 1 inch on the map is one million inches, or almost 26 kilometers on the surface of the moon.
These maps will help planetary scientists study these worlds, serving as a basis for geologic interpretations, and help estimate the ages of surface regions, and aid in deciphering the processes that formed the moons’ landscapes. But most importantly, with their accurate calculation of latitude and longitude, these maps allow scientists to easily find, and refer to, features of interest on the moons’ surfaces.
While Cassini has not been able to image every portion of the surfaces of Saturn’s moons, the Imaging Team has been able to combine images from the Voyager mission to help fill in any voids in Cassini data.
Now that they atlases are being assembled, the next task for the Cassini scientists will be to name the features on the moons. This is usually done using names and locations from various mythologies from different cultures. Features from Dione will be named from Virgil’s “Aeneid.”
CICLOPS is located at the Space Science Institute in Boulder, Colorado. The lab’s director and Cassini imaging team leader, Carolyn Porco said, “Both robotic and human travelers to Saturn in the future will surely rely on this growing collection of maps and their derivatives to find their way among the moons of Saturn.”
Reading something like this makes me hopeful that we’re no longer in the infant stage of our understanding of our solar system: we’ve been patient and observant while growing in our knowledge. Scientists have discovered a wave pattern, or oscillation, in Saturn’s atmosphere only visible from Earth every 15 years. This discovery was made only because we’ve been studying Saturn from ground based telescopes for about 22 years. Combined with the Cassini spacecraft’s observations of temperature changes in the giant planet’s atmosphere over time, we’re gaining a better understanding of Saturn and discovering not only how unique it is, but also that Saturn has something in common with Earth. Our own planet has these oscillations too, and so does Jupiter. “You could only make this discovery by observing Saturn over a long period of time,” said Glenn Orton, of JPL, lead author of the ground-based study. “It’s like putting together 22 years worth of puzzle pieces, collected by a hugely rewarding collaboration of students and scientists from around the world on various telescopes.”
The image above shows a pattern ripples back and forth like a wave within Saturn’s upper atmosphere. In this region, temperatures switch from one altitude to the next in a candy cane-like, striped, hot-cold pattern. The temperature “snapshot” shown in these two images captures two different phases of this wave oscillation: the temperature at Saturn’s equator switches from hot to cold, and temperatures on either side of the equator switch from cold to hot every Saturn half-year.
The image on the left was taken in 1997 and shows the temperature at the equator is colder than the temperature at 13 degrees south latitude. Conversely, the image on the right taken in 2006 shows the temperature at the equator is warmer.
Results from Cassini’s infrared camera indicate that Saturn’s wave pattern is similar to a pattern found in Earth’s upper atmosphere, which takes about two years. A similar pattern on Jupiter takes more than four Earth years. The new Saturn findings add a common link to the three planets.
Cassini scientists hope to find out why this phenomenon on Saturn changes with the seasons, and why the temperature switchover happens when the sun is directly over Saturn’s equator.
