9 Essential Facts About Saturn

This portrait looking down on Saturn and its rings was created from images obtained by NASA's Cassini spacecraft on October 10, 2013.
This portrait looking down on Saturn and its rings was created from images obtained by NASA's Cassini spacecraft on October 10, 2013.
NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic

Saturn is the planet you always drew in elementary school because without those rings, it's just a circle. But what is Saturn, anyway, and what makes it special to planetary scientists? Now is a good time to find out: On September 15, the scientists who operate the Cassini spacecraft—which they've used to study the gas giant for 13 years—are going to intentionally destroy Cassini by sending it on a crash course with Saturn. The data it will send back before it meets its fiery demise will be priceless.

Mental Floss is going to be inside mission control at NASA's Jet Propulsion Laboratory in Pasadena, California, as the scientists send Cassini on its grand finale mission. We'll have a full dispatch for you. In anticipation, we spoke to Saturn experts to find out what you need to know about the planet before Cassini takes its final plunge.

1. SATURN BY THE NUMBERS.

At 75,000 miles across, Saturn is nearly 10 times larger than Earth and the second-largest planet in the solar system, behind its neighbor, Jupiter. It is called a gas giant, meaning it is really big and made mostly of gas: in this case, hydrogen and helium. The deeper you get into Saturn, the greater the pressure and heat. How bad could it be, you ask? Bad enough that hydrogen exists as a liquid metal near the planet's core. In other words, don't expect astronauts to plant flags down there anytime soon. One Saturn year lasts about 30 Earth years, and one Saturn day is, well …

2. THE LENGTH OF A SATURNIAN DAY IS A MYSTERY.

The spacecraft Cassini has been operating in the Saturnian system for 13 years doing extraordinary science—and yet the length of a day on Saturn remains elusive. Is it 10 hours and 39 minutes, as suggested by data from Voyager 2 in 1981? Or is it 10 hours and 47 minutes, as Cassini data suggested when the spacecraft first arrived at Saturn in 2004? Or is it 10 hours 33 minutes, as later data suggested?

The problem is that Saturn keeps giving new answers. There are no continents spinning around for scientists to set a stopwatch to; cloud orbits are unreliable; and measurements of the planet's radio radiation and magnetic fields have proven equally frustrating. As Cassini completes its final orbits, it is collecting up-close Saturn data that might finally answer the question. No matter the number to be determined, 10 hours and change is a tremendous speed for a planet of Saturn's size to be spinning, and it affects even the planet's shape; its poles are flattened as a result of its rotation.

3. SATURN HAS SEASONS.

Visiting space aliens would never confuse Saturn with Earth, though the two planets do have one interesting shared characteristic: both are tilted to similar degrees relative to the equator of the Sun. Earth is tilted at 23.5 degrees; Saturn is tilted at 26.7 degrees. Axial tilt is the reason we experience seasons, and Saturn is no different (though the leaves there don't change color due to a pronounced lack of trees). Saturn experienced summer solstice four months ago, marking its maximum axial tilt toward the Sun and making it midsummer in Saturn's northern hemisphere. It will reach Autumn equinox in May 2025.

4. HERE'S MORE ABOUT CASSINI, NASA'S MOST AMBITIOUS PLANETARY MISSION EVER.

After 20 years in space—seven years en route to Saturn and 13 years in orbit around it—the Cassini spacecraft is nearly out of fuel for its thrusters. Rather than enter a permanent orbit around Saturn as an artificial satellite, or sent on an intercept course with Uranus, both risky endeavors, Cassini will burn up like a shooting star when it plunges into the depths of Saturn on September 15. For the past six months, Cassini has been taking daring dives through Saturn's rings in a series of 22 orbits, the last of which will send it on an impact course with the planet. As it speeds into the gas giant, it will return data on the composition of Saturn's atmosphere. Cassini's death mission will protect the moons Enceladus and Titan from contamination by Earth germs. 

5. ENJOY TERRIBLE WEATHER? YOU'D LOVE LIFE ON SATURN.

"Saturn has these absolutely massive storms once every few decades," says Sarah Hörst, a planetary scientist at Johns Hopkins University, "and we actually got to see one of them happen because we've been there so long." Scientists already knew about the storms from Earth-based observation, but close-up study made possible by Cassini gave new insights on how they work and what they do. "These massive storms actually pull up a lot of material from deeper in the atmosphere—stuff that we can't usually see or measure," she tells Mental Floss. This material consists of gases from deep within the planet's atmosphere. Saturn's storms cause dramatic temperature changes, and even have lightning. "If you were somehow managing to stand inside of Saturn's atmosphere, some of the storms would feel quite familiar, and some of these longer-lived storms, these vortexes, are somewhat related to a hurricane."

6. IT HAS A CORE, BUT DETAILS ABOUT IT ARE HAZY.

Saturn has a rocky core surrounded by liquid metallic hydrogen, though the finer details of the planet's interior remain elusive. At Jupiter, NASA's Juno mission is hard at work determining the nature of that planet's core. The 22 proximal orbits of Cassini's "grand finale" have a configuration similar to those of Juno, and scientists hope that data from these orbits can be used with Juno data to learn more about Saturn's interior. "The general picture that there's rocky stuff down there, probably metallic hydrogen, isn't really going to change," says Hörst. "The details of exactly how it looks and where its phase changes are—those types of things—will hopefully be worked out a bit more before Cassini ends."

7. YOU CAN SEE SATURN FROM YOUR BACKYARD.

When the skies are conducive to viewing, even a modest telescope can allow you to see Saturn. It will look just like you imagine: a ball surrounded by a distinctive ring structure. It will even "feel" three dimensional (because it is, of course) in a way that Jupiter or Mars will not. Your telescope might even allow you to spot Titan, Saturn's largest moon. Sky & Telescope offers a guide to help you see Saturn in all its glory.

8. ITS MOONS MIGHT BE YOUNGER THAN SOME DINOSAUR FOSSILS.

Earth's moon is about 4.5 billion years old. Saturn's moons are mere infants in comparison: possibly as young as 100 million years old. Matija Cuk, a research scientist at SETI, modeled the orbital evolution of the Saturn system, and found that the orbital shifts of the moons over time, and the gravitational influences of the moons over each other, suggest origins when dinosaurs ruled the Earth. "If calculations predict that something happened in the past and you don't see it, maybe it never happened," he tells Mental Floss. One scenario sees a different inner moon system whose orbits resonated and eventually crossed, causing the moons to collide. The current system of moons then assembled from the debris.

Those rings around Saturn might not be very old, either, and might be related to the young moons. "The rings might be pieces of broken up moons," he says. "You figure out how old the rings are and you can figure out the last time the moons were broken up and when some of them were put back together."

9. THERE'S A GOOD CHANCE THAT LIFE EXISTS ON THOSE MOONS.

Enceladus, one of Saturn's moons, possesses a global saltwater ocean surrounded by an icy crust. That ocean is in direct contact with a rocky core. Saltwater touching rock is exciting because it allows for interesting chemistry—including the sort that might be conducive to life. Adding to the excitement are hydrothermal vents on the sea floor, spewing water, minerals, and nutrients heated by geothermal activity. Better yet, that ocean is being blasted into space through massive geysers. This means NASA can get to the water, sample it, and hopefully, find life.

Titan, another moon of Saturn, also possesses the right stuff for life—and not boring old liquid water life, either, but something wholly alien: a methane-based life form. Key to such life would be the presence of the molecule acrylonitrile, now known to exist on Titan. The European Space Agency landed the Huygens probe on Titan in 2005, and Cassini later discovered several massive liquid methane lakes on that world. The next step is to send a submarine there and get to work.

Could an Astronaut Steal a Rocket and Lift Off, Without Mission Control?

iStock
iStock

C Stuart Hardwick:

Not with any rocket that has ever thus far carried a person into orbit from Earth, no. Large rockets are complex, their launch facilities are complex, their trajectories are complex, and the production of their propellants is complex.

Let me give you one simple example:

  • Let’s say astro-Sally is the last woman on Earth, and is fully qualified to fly the Saturn-V.
  • Further, let’s say the Rapture (which as I understand it, is some sort of hip-hop induced global catastrophe that liquefies all the people) has left a Saturn-V sitting on the pad, raring to go.
  • Further, let’s grant that, given enough time, astro-Sally can locate sufficient documentation to operate the several dozen controls needed to pump the first stage propellant tanks full of kerosene.
  • Now what? Oxidizer, right? Wrong. First, she has to attend to the batteries, oxygen, hydrogen, and helium pressurant tanks in her spacecraft, otherwise it’s going to be a short, final flight. And she’ll need to fill the hypergolics for the spacecraft propulsion and maneuvering systems. If she screws that up, the rocket will explode with her crawling on it. If she gets a single drop of either of these on her skin or in her lungs, she’ll die.
  • But okay, maybe all the hypergolics were already loaded (not safe, but possible) and assume she manages to get the LOX, H2, and HE tanks ready without going Hindenburg all over the Cape.
  • And…let’s just say Hermione Granger comes back from the Rapture to work that obscure spell, propellantus preparum.
  • All set, right? Well, no. See, before any large rocket can lift off, the water quench system must be in operation. Lift off without it, and the sound pressure generated by the engines will bounce off the pad, cave in the first stage, and cause 36 stories of rocket to go “boom.”
  • So she searches the blockhouse and figures out how to turn on the water quench system, then hops in the director’s Tesla (why not?) and speeds out to the pad, jumps in the lift, starts up the gantry—and the water quench system runs out of water ... Where’d she think that water comes from? Fairies? No, it comes from a water tower—loaded with an ample supply for a couple of launch attempts. Then it must be refilled.

Now imagine how much harder this would all be with the FBI on your tail.

Can a rocket be built that’s simple enough and automated enough to be susceptible to theft? Sure. Have we done so? Nope. The Soyuz is probably the closest—being highly derived from an ICBM designed to be “easy” to launch, but even it’s really not very close.

This post originally appeared on Quora. Click here to view.

The Science Behind Why the Earth Isn't Flat

Earth as captured from near the lunar horizon by the Lunar Reconnaissance Orbiter in 2015.
Earth as captured from near the lunar horizon by the Lunar Reconnaissance Orbiter in 2015.
NASA

On March 24, 2018, flat-earther Mike Hughes set out prove that the Earth is shaped like a Frisbee. The plan: Strap himself to a homemade steam-powered rocket and launch 52 miles into sky above California’s Mojave Desert, where he'd see Earth's shape with his own eyes.

It didn't matter that astronauts like John Glenn and Neil Armstrong had been to space and verified that the Earth is round; Hughes didn't believe them. According to The Washington Post, Hughes thought they were "merely paid actors performing in front of a computer-generated image of a round globe."

The attempt, ultimately, was a flop. He fell back to Earth with minor injuries after reaching 1875 feet—not even as high as the tip of One World Trade Center. For the cost of his rocket stunt ($20,000), Hughes could have easily flown around the world on a commercial airliner at 35,000 feet.

Hughes isn't alone in his misguided belief: Remarkably, thousands of years after the ancient Greeks proved our planet is a sphere, the flat-Earth movement seems to be gaining momentum. "Theories" abound on YouTube, and the flat-Earth Facebook page has some 194,000 followers.

Of course, the Earth isn't flat. It's a sphere. There is zero doubt about this fact in the real, round world. To say the evidence is overwhelming is an understatement.

HOT SPINNING BODIES

Not every celestial body is a sphere, but round objects are common in the universe: In addition to Earth and all other known large planets, stars and bigger moons are also ball-shaped. These objects, and billions of others, have the same shape because of gravity, which pulls everything toward everything else. All of that pulling makes an object as compact as it can be, and nothing is more compact than a sphere. Say, for example, you have a sphere of modeling clay that is exactly 10 inches in diameter. No part of the mass is more than 5 inches from the center. That's not the case with any other shape—some part of the material will be more than 5 inches from the center of the mass. A sphere is the smallest option.

Today the Earth is mostly solid with a liquid outer core, but when the planet was forming, some 4.5 billion years ago, it was very hot and behaved like more like a fluid—and was subject to the squishing effects of gravity.

And yet, the Earth isn't a perfect sphere; it bulges slightly at the equator. "Over a long time-scale, the Earth acts like a highly viscous fluid," says Surendra Adhikari, a geophysicist at the Jet Propulsion Laboratory in Pasadena, California. The Earth has been spinning since it was formed, and "if you have a spinning fluid, it will bulge out due to centrifugal forces." You can see evidence for this at the equator, where the Earth's diameter is 7926 miles—27 miles larger than at the poles (7899 miles). The difference is tiny—just one-third of 1 percent.

THE SHADOW KNOWS

The ancient Greeks figured out that Earth was a sphere 2300 years ago by observing the planet's curved shadow during a lunar eclipse, when the Earth passes between the Sun and the Moon. Some flat-Earth believers claim the world is shaped like a disk, perhaps with a wall of ice along the outer rim. (Why no one has ever seen this supposed wall, let alone crashed into it, remains unexplained.) Wouldn't a disk-shaped Earth also cast a round shadow? Well, it would depend on the orientation of the disk. If sunlight just happened to hit the disk face-on, it would have a round shadow. But if light hit the disk edge-on, the shadow would be a thin, straight line. And if the light fell at an oblique angle, the shadow would be a football–shaped ellipse. We know the Earth is spinning, so it can't present one side toward the Sun time after time. What we observe during lunar eclipses is that the planet's shadow is always round, so its shape has to be spherical.

The ancient Greeks also knew Earth's size, which they determined using the Earth's shape. In the 2nd century BCE, a thinker named Eratosthenes read that on a certain day, the people of Syene, in southern Egypt, reported seeing the Sun directly overhead at noon. But in Alexandria, in northern Egypt, on that same day at the same time, Eratosthenes had observed the Sun being several degrees away from overhead. If the Earth were flat, that would be impossible: The Sun would have to be the same height in the sky for observers everywhere, at each moment in time. By measuring the size of this angle, and knowing the distance between the two cities, Eratosthenes was able to calculate the Earth's diameter, coming up with a value within about 15 percent of the modern figure.

And when Columbus set sail from Spain in 1492, the question wasn't "Would he fall off the edge of the world?"—educated people knew the Earth was round—but rather, how long a westward voyage from Europe to Asia would take, and whether any new continents might be found along the way. During the Age of Exploration, European sailors noticed that, as they sailed south, "new" constellations came into view—stars that could never be seen from their home latitudes. If the world were flat, the same constellations would be visible from everywhere on the Earth's surface.

Finally, in 1522, Ferdinand Magellan's crew became the first people to circle the globe. Like Columbus, Magellan also set off from Spain, in 1519, heading west—and kept generally going west for the next three years. The expedition wound up back at the starting point (though without Magellan, who was killed during a battle in the Philippines). And speaking of ships and seafaring: One only needs to watch a tall ship sailing away from port to see that its hull disappears before the top of its mast. That happens because the ship is traveling along a curved surface; if the Earth were flat, the ship would just appear smaller and smaller, without any part of it slipping below the horizon.

THE EVIDENCE IS ALL AROUND (AND ALL ROUND)

But you don't need a ship to verify the Earth's shape. When the Sun is rising in, say, Moscow, it's setting in Los Angeles; when it's the middle of the night in New Delhi, the Sun is shining high in the sky in Chicago. These differences occur because the globe is constantly spinning, completing one revolution per day. If the Earth were flat, it would be daytime everywhere at once, followed by nighttime everywhere at once.

You also experience the Earth's roundness every time you take a long-distance flight. Jetliners fly along the shortest path between any two cities. "We use flight paths that are calculated on the basis of the Earth being round," Adhikari says. Imagine a flight from New York to Sydney: It would typically head northwest, toward Alaska, then southwest toward Australia. On the map provided in your airline's in-flight magazine, that might look like a peculiar path. But wrap a piece of string around a globe, and you'll see that it’s the shortest possible route.

"If the Earth were flat," Adhikari says, "the trajectory would be completely different." How different depends on which way the globe is sliced into a flattened map, but if it looked like it does on a Mercator-projection map, it might head east and pass over Africa.

Engineers and architects also take the Earth's curvature into account when building large structures. A good example is the towers that support long suspension bridges such as the Verrazano Narrows bridge in New York City. Its towers are slightly out of parallel with each other, the tops being more than 1.5 inches further apart than their bases. If the Earth were flat, the bottom of the towers would be separated by the exact same distance as the top of the towers; the planet's curvature forces the tops of the towers apart.

And for the last half-century, we've had eyewitness and photographic proof of the Earth's shape. In December 1968, the crew of Apollo 8 left Earth for the Moon. When they looked out of the Command Module windows, they saw a blue-and-white marble suspended against the blackness of space. On Christmas Eve, lunar module pilot William Anders snapped the famous "Earthrise" photograph. It gave us an awe-inspiring perspective of our round planet that was unprecedented in human history—but it wasn't a surprise to anyone.

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