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.


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 …


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.


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.


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. 


"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."


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."


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.


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."


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.

A Super Worm Moon Is Coming on the First Day of Spring


So far, 2019 has been a treat for astronomy fans. The last supermoon (and the brightest one of the year) was visible on February 19, and the next one is set to appear barely a month later on Wednesday, March 20, the first day of spring. Instead of the snow moon that came last month, this upcoming celestial event will be a super worm moon.

What is a supermoon?

A supermoon is defined as the Moon's seemingly larger size when viewed from Earth. The Moon is constantly circling our planet, and its apparent size in the night sky changes depending on where it is in its oval-shaped orbit. Its perigee is the point in its orbit that brings it closest to Earth; when the Moon reaches its perigee on a day when it's full, it's officially a supermoon.

Full moons also have different nicknames based on the time of year they occur. Last month's event was a snow moon: the first full moon that appears in February. March's supermoon will be a worm moon. A worm moon is usually the last full moon of winter, and it's named after the earthworms that start wriggling their way through the soil as spring approaches. In this case, the full moon coincides with the vernal equinox—the start of the spring season. The last time a full moon coincided with the first day of spring was March 20, 1981.

When to watch the next supermoon

The best time to catch the next supermoon are the nights of Tuesday, March 19 and Wednesday, March 20. At 2:48 p.m. on Tuesday, the Moon will reach its perigee, and at 8:43 p.m. ET on Wednesday, the Moon will be at its fullest. The Moon will also appear especially close and bright on the days surrounding the spring equinox.

Supermoons have felt like a common occurrence this year, with three appearing in the first three months in 2019. But after the worm moon, they will be much rarer: The next supermoon with a full moon won't happen until 2020. There will, however, be two new moon supermoons in August, but even though the Moon will be at the closest point in its orbit during the events, it won't be visible in the night sky.

15 Facts About Nicolaus Copernicus


Polish astronomer and mathematician Nicolaus Copernicus fundamentally altered our understanding of science. Born on February 19, 1473, he popularized the heliocentric theory that all planets revolve around the Sun, ushering in the Copernican Revolution. But he was also a lifelong bachelor and member of the clergy who dabbled in medicine and economics. Dive in to these 15 facts about the father of modern astronomy.

1. He came from a family of merchants and clergy.

Some historians believe that Copernicus's name derives from Koperniki, a village in Poland named after tradesmen who mined and sold copper. The astronomer's father, also named Nicolaus Copernicus, was a successful copper merchant in Krakow. His mother, Barbara Watzenrode, came from a powerful family of merchants, and her brother, Lucas Watzenrode the Younger, was an influential Bishop. Two of Copernicus's three older siblings joined the Catholic Church, one as a canon and one as a nun.

2. He was a polyglot.

Growing up, Copernicus likely knew both Polish and German. When Copernicus's father died when he was around 10, Lucas Watzenrode funded his nephew's education and he started learning Latin. In 1491, Copernicus began studying astronomy, math, philosophy, and logic at Krakow University. Five years later, he headed to modern Italy's Bologna University to study law, where he likely picked up some Italian. During his studies, he also read Greek, meaning modern historians think he knew or understood five languages.

3. He wasn't the first person to suggest heliocentrism ...

 A page from the work of Copernicus showing the position of planets in relation to the Sun.
A page from the work of Copernicus showing the position of planets in relation to the Sun.
Hulton Archive, Getty Images

Copernicus is credited with introducing heliocentrism—the idea that the Earth orbits the sun, rather than the sun orbiting the Earth. But several ancient Greek and Islamic scholars from various cultures discussed similar ideas centuries earlier. For example, Aristarchus of Samos, a Greek astronomer who lived in the 200s BCE, theorized that Earth and other planets revolved around the Sun.

4. … but he didn't fully give credit to earlier scholars.

To be clear, Copernicus knew of the work of earlier mathematicians. In a draft of his 1543 manuscript, he even included passages acknowledging the heliocentric ideas of Aristarchus and other ancient Greek astronomers who had written previous versions of the theory. Before submitting the manuscript for publication, though, Copernicus removed this section; theories for the removal range from wanting to present the ideas as wholly his own to simply switching out a Latin quote for a "more erudite" Greek quote and incidentally removing Aristarchus. These extra pages weren't found for another 300-some years.

5. He made contributions to economics.

He's known for math and science, but Copernicus was also quite the economist. In 1517, he wrote a research paper outlining proposals for how the Polish monarch could simplify the country's multiple currencies, especially in regard to the debasement of some of those currencies. His ideas on supply and demand, inflation, and government price-fixing influenced later economic principles such as Gresham's Law (the observation that "bad money drives out good" if they exchange for the same price; for example, if a country has both a paper $1 bill and a $1 coin, the value of the metal in the coin is higher than the value of the cotton and linen in the bill, and thus the bill will be spent as currency more because of that) and the Quantity Theory of Money (the idea that the amount of money in circulation is proportional to how much goods cost).

6. He was a physician (but he didn't have a medical degree).

After studying law, Copernicus traveled to the University of Padua so he could become a medical advisor to his sick uncle, Bishop Watzenrode. Despite spending two years studying medical texts and learning anatomy, Copernicus left medical school without a doctoral degree. Nevertheless, he traveled with his uncle and treated him, as well as other members of the clergy who needed medical attention.

7. He was probably a lifelong bachelor …

An etching of Copernicus, circa 1530.
An etching of Copernicus, circa 1530.
Hulton Archive, Getty Images

As an official in the Catholic Church, Copernicus took a vow of celibacy. He never married and was most likely a virgin (more on that below), but children were not completely absent from his life: After his older sister Katharina died, he became the financial guardian of her five children, his nieces and nephews.

8. … But he may have had an affair with his housekeeper.

Copernicus took a vow of celibacy, but did he keep it? In the late 1530s, the astronomer was in his sixties when Anna Schilling, a woman in her late forties, began living with him. Schilling may have been related to Copernicus—some historians think he was her great uncle—and she worked as his housekeeper for two years. For unknown reasons, the bishop he worked under admonished Copernicus twice for having Schilling live with him, even telling the astronomer to fire her and writing to other church officials about the matter.

9. He attended four universities before earning a degree.

A Polish stamp of Nicolaus Copernicus.

Copernicus spent over a decade studying at universities across Poland and Italy, but he usually left before he got his degree. Why skip the diplomas? Some historians argue that at the time, it was not unusual for students to leave a university without earning a degree. Moreover, Copernicus didn't need a degree to practice medicine or law, to work as a member of the Catholic Church, or even to take graduate or higher level courses. 

But right before returning to Poland he received a doctorate in canon law from the University of Ferrara. According to Copernicus scholar Edward Rosen this wasn't exactly for scholarly purposes, but that to "show that he had not frittered his time away on wine, women, and song, he had to bring home a diploma. That cost much less in Ferrara than in the other Italian universities where he studied."

10. He was cautious about publicizing his views.

During Copernicus's lifetime, nearly everyone believed in geocentrism—the view that the Earth lies at the center of the universe. Despite that, in the 1510s Copernicus wrote Commentariolus, or "the Little Commentary," a short text that discussed heliocentrism and was circulated amongst his friends. It was soon found circulating further afield, and it's said that Pope Clement VII heard a talk about the new theory and reacted favorably. Later, Cardinal Nicholas Schönberg wrote a letter of encouragement to Copernicus, but Copernicus still hesitated in publishing the full version. Some historians propose that Copernicus was worried about ridicule from the scientific community due to not being able to work out all of the issues heliocentrism created. Others propose that with the rise of the Reformation, the Catholic Church was increasingly cracking down on dissent and Copernicus feared persecution. Either way, he didn't make his complete work public until 1543.

11. He published his work on his deathbed.

An antique bookseller displays a rare first edition of Nicolaus Copernicus' revolutionary book on the planet system.
An antique bookseller displays a rare first edition of Nicolaus Copernicus' revolutionary book on the planet system, at the Tokyo International antique book fair on March 12, 2008. The book, published in 1543 and entitled in Latin "De Revolutionibus Orbium Coelestium, Libri VI," carries a diagram that shows the Earth and other planets revolving around the Sun, countering the then-prevailing geocentric theory.

Copernicus finishing writing his book explaining heliocentrism, De Revolutionibus Orbium Coelestium (On the Revolutions of Celestial Orbs), in the 1530s. When he was on his deathbed in 1543, he finally decided to publish his controversial work. According to lore, the astronomer awoke from a coma to read pages from his just-printed book shortly before passing away.

12. Galileo was punished for agreeing with Copernicus.

Copernicus dedicated his book to the Pope, but the Catholic Church repudiated it decades after it was published, placing it on the Index of Prohibited Books—pending revision—in 1616. A few years later, the Church ended the ban after editing the text to present Copernicus's views as wholly hypothetical. In 1633, 90 years after Copernicus's death, the Church convicted astronomer Galileo Galilei of "strong suspicion of heresy" for espousing Copernicus's theory of heliocentrism. After a day in prison, Galileo spent the rest of his life under house arrest.

13. There's a chemical element named after him.

Take a look at the periodic table of elements, and you might notice one with the symbol Cn. Called Copernicium, this element with atomic number 112 was named to honor the astronomer in 2010. The element is highly radioactive, with the most stable isotope having a half life of around 30 seconds.

14. Archaeologists finally discovered his remains in 2008.

Frombork Cathedral

Although Copernicus died in 1543 and was buried somewhere under the cathedral where he worked, archaeologists weren't sure of the exact location of his grave. They performed excavations in and around Frombork Cathedral, finally hitting pay dirt in 2005 by finding part of a skull and skeleton under the church's marble floor, near an altar. It took three years to complete forensic facial reconstruction and compare DNA from the astronomer's skeleton with hair from one of his books, but archeologists were able to confirm that they had found his skeleton. Members of the Polish clergy buried Copernicus for a second time at Frombork in 2010.


The Nicolaus Copernicus Monument in Warsaw, Poland.

A prominent statue of the astronomer, simply called the Nicolaus Copernicus Monument, stands near the Polish Academy of Sciences in Warsaw, Poland. There are also replicas of this monument outside Chicago's Adler Planetarium and Montreal's Planétarium Rio Tinto Alcan. Besides monuments, Copernicus also has a museum and research laboratory—Warsaw's Copernicus Science Centre—dedicated to him.