In the top layer, which has an air pressure much like Earth’s, the clouds are made up of ammonia ice. In the layer underneath, where temperatures are already approaching zero degrees Celsius, pressures are similar to 100 meters below sea level on Earth. This is the stomping ground of water-ice clouds. Below that is a layer of ammonium-hydrosulfide clouds, transitioning finally into an area characterized by ammonia in an aqueous solution.
Similar to Jupiter, there isn’t a surface to speak of. Pressure and temperature increase steadily, and the properties of the matter change accordingly. Under increasing pressure, at some point, hydrogen will take on metallic properties, until finally you reach a solid rocky core that might have a mass between 9 and 20 times the mass of the Earth and is up to 11,700 degrees Celsius.
Saturn produces about 2.5 times more heat than it receives from the Sun. The mechanisms that produce this heat are thought to include the gradual shrinking of the planet, which releases gravitational energy. But that wouldn’t account for all the heat it radiates—unlike Jupiter.
It is also thought that droplets of helium, which slowly migrate from the surrounding shell toward the core and generate frictional heat in the process, also contribute to the balance of energy. Thus, over time, a mantle of helium might have formed around the core.
Saturn’s Ring System
Saturn weighs as much as 95 Earths, and yet, as previously mentioned, it is the planet with the lowest density in the solar system. Its average density is less than one third that of water. Because its matter is so easily compressed, the Ringed Planet also has the most flattened shape. At the equator, its diameter is ten percent greater than from pole to pole. Saturn easily makes up for this somewhat unattractive figure with its most prominent feature—its ring system. Since it was first discovered, we’ve learned that all gas planets have rings. But no planet has rings as impressive as Saturn’s.
That is primarily due to their composition. The rings, which are, on average, only 20 kilometers thick, consist of around 93 percent very pure water ice, which reflects incident light very well. They extend up to 120,000 kilometers out into space. That’s approximately one third the distance from the Earth to the Moon.
Astronomers have counted about 100,000 individual rings, which are generally sharply separated from each other. Wherever small moons have smuggled themselves into the disk, they have cleared out small swaths of very low particle density.
The particles themselves are between one-thousandth of a millimeter and a few meters in diameter. Their total mass is around 30 quintillion tons. That sounds like a lot, but it’s less than half the mass of the 396-kilometers diameter moon Mimas, which created the clearly visible Cassini partition in the ring system.
The rings probably formed at the same time as Saturn. They are likely the remnants of a much more massive accretion disk that also formed Saturn’s moons. That is the currently preferred theory, in any case. One older theory conjectured that another moon used to orbit Saturn but was ripped apart by Saturn’s gravitational forces.
The Moons of Saturn
Of the 82 known moons of Saturn, only 13 are more significant than 50 kilometers across. At least 38 of the satellites orbit the planet on irregular orbits, that is, in the direction opposite to the others, or at a different angle of inclination. Probably not all of them were created with Saturn—some were likely captured by the planet.
Because the rings are made up of lots of different objects, some bigger than the other, it’s impossible to count the number of Saturn’s moons exactly—there’s no fixed limit for when an astronomical body counts as a moon. Most of the larger satellites, among them Rhea and Dione, are made up primarily from water ice. Some also have a rocky core.
Mimas – Where Star Wars and Pac-Man Meet
On the top-hits list of Saturn’s moons, Mimas would just make it into the top 20. At the same time, it is the smallest astronomical body known to have a spherical shape due to self-gravitation. The moon, which has a diameter of approximately 400 kilometers, is made up primarily of water ice. Its surface displays the scar of a giant wound—the Herschel crater, with a diameter of 130 kilometers. The impact that formed this crater appears to have nearly destroyed Mimas—at least that’s the implication from the fracture lines on the opposite side of the moon.
The crater also makes Mimas resemble the Imperial Death Star from Star Wars.
Another pop-culture symbol also makes an appearance on Mimas. Mapping the temperature distribution on the surface of Mimas produces an image that looks a lot like Pac-Man about to eat a dot. The fact that heat is distributed differently than predicted is a mystery to researchers. They conjecture that the material covering the surface must conduct or store heat differently.
Enceladus – The Moon of Cryovolcanoes
Enceladus is one of the brightest astronomical bodies in the solar system. Its albedo, or reflective power, is almost 100 percent. Covered in fresh, clean ice, Enceladus, which is only 500 kilometers in diameter, is easy to see. But when almost all sunlight is reflected, not much is left to heat the surface. At minus 200 degrees Celsius, a visitor would have to contend with frost and extremely cold conditions.
The phenomenon raises the question of why Enceladus, and none of the other moons, is so bright. Its sibling moons have become darker over millions of years due to cosmic dust from space, but not Enceladus. Therefore, there must be a source that is continuously providing new ice crystals. It must also be a source for its thin atmosphere, because Enceladus itself is not large enough to hold onto a layer of air.
After many attempts to solve the puzzle, the Cassini probe finally found the source in 2005. It photographed plumes of ice crystals erupting in an area near its South Pole. The site is marked by so-called ‘Tiger Stripes,’ deep fractures in Enceladus’s crust. At various points in these fractures, a not yet thoroughly explained mechanism produces ice plumes that eject matter across the entire moon.
One of the possible causes might be a warm ocean under the surface. If the pressure increases too much, water will spray like an Icelandic geyser at enormous speeds—1600 kilometers per hour—out of the underground chambers and then instantly freeze. The crystals would thus reach heights of up to 500 kilometers and would also feed parts of Saturn’s rings. The giant plumes must be a fabulous sight.
The fact that Enceladus is not frozen completely solid is Saturn’s fault. Saturn’s gravitational forces knead Enceladus’s rocky core and icy mantle so vigorously that they generate heat in the layers. As shown during a close flyby by the Cassini probe in 2008, the composition of the plumes is strikingly similar to that of comets, with components of carbon compounds and organic molecules. This finding sparked the speculation about whether life might possibly be found in a warm underground ocean on Enceladus—in any case, energy and the chemical requirements appear to be in place.
Titan – The Methane Earth
A dense atmosphere, weather phenomena like rain and snow, dunes at the equator, mountains up to 2,000 meters high, and large lakes and rivers—Saturn’s moon Titan has many similarities to Earth. Even though it’s only slightly larger than Mercury, the planet closest to the Sun, Titan is the most Earth-like astronomical body in the solar system. If this has you ready to buy some lakefront property on Ontario Lacus, which is about as large as Connecticut, I’d advise you to read the fine print first. There are many small—and vast—differences when compared to the conditions here on Earth.
For one thing, you can leave your surfboard at home. The lake’s biggest waves are a millimeter high—at least, they were when NASA’s Cassini probe imaged the lake with radar. You can also skip packing your diving equipment, because the lake is, on average, only about one-half to three meters deep. However, diving equipment might come in handy for surviving outdoors because, even though the moon has only a seventh of Earth’s force of gravity, its exceptionally dense atmosphere would weigh down anything and anyone visiting it.
On the surface, you would have to deal with
air pressure one and a half times greater than that on Earth. Imagine living at the bottom of a swimming pool. Instead of a sunny and beach-like atmosphere, it would probably smell more like a gas station, because the air is made up of 98 percent nitrogen mixed with argon, methane, and other hydrocarbons. Unfortunately, there’s no oxygen in the atmosphere for us to breathe.
At least Titan has a dense atmosphere. No other moon can boast of such a feature, and because it’s also a little bigger than Mercury, it could even pass as a planet.
The fact that it rains from time to time on Titan shouldn’t be a problem for those who are used to vacationing in the Pacific Northwest. The average temperatures, however, are much lower than on the West Coast of the United States, hanging around minus 180 degrees Celsius. At these temperatures, the raindrops on your umbrella wouldn’t be water, of course, but instead liquid hydrocarbons, such as methane and ethane.
Researchers also believe that the weather cycle on Titan would be significantly different from that on Earth. For one, the atmosphere can hold a lot more liquid, and due to the minimal solar radiation, the liquid methane would also evaporate much more slowly. Therefore, 100-year-long droughts are likely to be followed by short-term floods. In the equatorial region, however, there’s no rain. Instead, large molecules of complex carbon compounds, produced by interactions between methane and sunlight, crystallize to form dunes.
According to NASA researchers, the astronomical body’s meteorology might have even determined the moon’s shape. It is significantly flatter than would be predicted from its rotational velocity. Thus, it must have either been moving about one-third faster around its axis earlier in its life, or been subjected to rainfall from the ethane present in the atmosphere, which would have made the polar caps heavier. This additional mass at the poles could have caused the flattening.
Surface structures are also formed by Titan’s weather. For example, close to the equator, winds have shaped dunes composed of mainly hydrocarbon sand and are 100 meters high and extend for hundreds of kilometers. These areas of sand were probably filled with liquid at an earlier stage in Titan’s history.
Real lakes are found closer to the poles. Two examples: Ontario Lacus, which was mentioned above, has a surface area of 15,000 square kilometers; and Kraken Mare has surface dimensions similar to the Caspian Sea, or Lake Superior and Lake Ontario combined.
Finding water ice is not a problem. At the surface temperatures on Titan it is hard as stone. Researchers have even found volcanism on the moon—but instead of lava, water is spewed out of Titan’s volcanoes. This water comes from a giant, underground reservoir, an ocean that scientists believe to be 45 to 100 kilometers deep.
One of the latest discoveries of the Cassini probe, reported in December 2012, is an approximately 400-kilometer-long river system. It includes a few branches, and runs along a crack that finally empties into the methane lake, Ligeia Mare, which has a diameter of 500 kilometers. Researchers believe the lake is filled with a liquid mixture of ethane and methane, as data from Cassini’s spectrometer indicated in 2008 for Ontario Lacus.
The crack that the river follows does not necessarily indicate plate tectonics like on Earth. However, researchers believe that the cracks in the rock were sufficient for creating such large methane lakes as Ligeia Mare. Instead of plate tectonics, the long-term shrinking of the moon might be responsible for the cracks. The moon’s core is still somewhat hotter than the surface, and it is cooling and therefore contracting. Like an air balloon, this contraction process leads to wrinkles and cracks in the outer skin.
Hyperion – The Flying Sponge
Hyperion might be mistaken for the cartoon character, SpongeBob SquarePants, because the moon has many characteristics of a sponge. A picture is worth more than a thousand words in this case. The moon is the second-largest astronomical body in the solar system with an irregular shape, trailing only Saturn’s Phoebe in that category. It is made up primarily of water ice but is covered by a layer of dark dust.
Like a sponge or Swiss cheese, Hyperion is enormously porous—about 30 to 40 percent of its interior consists of empty space. It may be a fragment broken off from a previously much larger moon. Because it is close to Titan, if it did break off from a larger moon, this event could have also enriched Titan’s atmosphere.
Iapetus – The Two-Faced Moon
At 42 percent the size of Earth’s moon, Iapetus is not tiny. It is famous for its pronounced color differences. The side pointing in the ‘direction of travel,’ that is, the front side when looking at the moon’s trajectory, is significantly darker than Iapetus’s rear side. Iapetus has a tidally locked rotation, so the same side is always pointing in the direction of travel. Today, we know that a layer of deposits—at most a half-meter thick—is responsible for the different colors.
These deposits were left behind when ice, which makes up 80 percent of Iapetus, dissipated (sublimated) on the strongly heated front side. Due to the weak gravitation, gaseous water can easily migrate to the colder rear side, where it re-condenses as ice, there and at the poles, and contributes to the bright color.
As a second distinctive feature, Iapetus also has a pronounced ridge around its equator. Here, a chain of mountains wraps three-quarters of the way around the moon, extending as high as 20 kilometers above their surroundings. Thus, Iapetus has some of the tallest mountains in the solar system. Researchers do not yet agree on how this ridge was formed.
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Glossary of Acronyms
AI – Artificial Intelligence
CoC – Commission of Commanders
EEG – ElectroEncephaloGram
g – g-force (gravitational force)
RC – Research Commission
RTG – Radioisotope Thermoelectric Generator
Metric to English Conversions
It is assumed that by the time the events of this novel take place, the United States will have joined the rest of the world and will be using the International System of Units, the modern form of the metric system.
Length:
centimeter = 0.39 inches
meter = 1.09 yards, or 3.28 feet
kilometer = 1093.61 yards, or 0.62 miles
Area:
square centimeter = 0.16 square inches
square meter = 1.20 square yards
square kilometer = 0.39 square miles
Weight:
gram = 0.04 ounces
kilogram = 35.27 ounces, or 2.20 pounds
Volume:
liter = 1.06 quarts, or 0.26 gallons
cubic meter = 35.31 cubic feet, or 1.31 cubic yards
Temperature:
To convert Celsius to Fahrenheit, multiply by 1.8 and then add 32
To convert Kelvin to Celsius, subtract 273.15
Excerpt: The Triton Disaster
5/23/2080, VSS Freedom
“What is that?”
Startled, Nick turned towards the sound of the voice. One of the passengers, the skinny bald one, was watching the radar image over his shoulder.
“During the flight, you should...” Nick began, but then shook his head. Here we go again, he thought. There wasn’t really anything wrong with people asking him questions during the flight. They were, in the end, paying for him to entertain them.
“Let me see...” He looked for the bald man’s name tag and read it. “Mr. Wiseman. We’ll find out shortly.”
He shifted the radar image to center on the shadow the man had spotted. Usually the autopilot handled the radar and Nick didn’t have to check it. The pilot only had to step in if something was endangering the ship’s flight path and the autopilot hadn’t determined a detour. In other words, never. Whatever was casting the shadow must have been rotating, since the intensity changed at a rate of approximately once per minute. Nick retrieved the orbital data and nodded. It was probably one of the Spacelink satellites a crazy billionaire had paid to
have fired into low orbit, way back when, only to just leave them up there when his company had gone bankrupt.
“Mr. Wiseman? This looks like an old Spacelink satellite. It’s a miracle it hasn’t burned up yet.”
It was strange, though. At such a low orbit, the atmosphere would have caused so much deceleration that the satellite should have fallen long ago. But during one of the launches the satellite deployment hadn’t gone as planned, so four of them had ended up in higher orbits. Nick remembered this only because it had delayed his own first launch into space by a month. NASA had wanted to be sure that the private firm had its technology under control.
“Spacelink?” the curious passenger asked.
“Yes, that’s what the low orbit suggests. If it were an active satellite, the radar would issue a warning.”
“Then that thing is worth a lot!”
“Well, after so much time it’s become electronic waste.”
“Didn’t you hear that one of the company founder’s vehicles was auctioned off at fifty million the other day? A salvage company brought it back from its Mars orbit.”
The man was right. The Spacelink founder’s fans still adored him, and the fact that most of the other satellites in the series had burned up would increase the value of this specimen significantly.
“I think, Mr. Wiseman, that we should note what the exact path of this gem is. Then, later on we can—”
“But why later?” interrupted the passenger. He had become so loud that four of his five fellow travelers stopped photographing from their portholes to look up at him.
Impact Page 27
