A Common Myth About Each Planet in Our Solar System

Poor Pluto. For 76 years, it held the prestigious title of the ninth planet in our solar system, the most distant from the sun. A captivating celestial object with a diameter about the same as the distance between New York and Houston, and an average temperature of -387°F. The ruler of five moons. The only planet named by an 11-year-old girl. Pluto certainly had its moments of grandeur.

But in 2006, astronomers at the International Astronomical Union stripped it of its planetary status. So, no, Pluto is no longer considered one of the planets in our solar system. However, the decision wasn’t as straightforward as it may seem. Let’s explore that debate and debunk a misconception about each of the currently recognized planets, as seen in an episode of Misconceptions on YouTube.

1. Misconception: Every astronomer agreed to strip Pluto of its planetary title.

As stated by the International Astronomical Union, a celestial body must meet three criteria to be recognized as a true planet in our solar system. First, it must orbit the sun, something Pluto definitely does. Second, it must be nearly spherical—check. And third, it must be the dominant gravitational force in its orbit, clearing the area of similarly sized objects (with a few exceptions). This is where Pluto fails. It still shares its space with other large objects in the Kuiper Belt, meaning it hasn't cleared its orbital zone. 

The union decided to reclassify Pluto as a dwarf planet, but this decision was highly contentious. Fewer than 5 percent of global astronomers participated in the vote, and many others disagreed with the criteria set by the International Astronomical Union. Public reaction was intense. Adults who had grown up learning about the nine planets were bewildered and upset. What should my very educated mother just serve us now?

Many esteemed scientists still believe Pluto should be considered a planet based on its size, shape, and orbit, regardless of the IAU’s decision. People hold … passionate views about Pluto. 

2. Myth: Mercury is the hottest planet.

Mercury, a small, rocky planet, is the closest to the sun and the tiniest planet in the entire solar system (excluding Pluto). Its elliptical orbit brings it as close as 29 million miles to the sun and as far as 43 million miles away. Despite its proximity, it’s not the hottest planet.

Mercury has a slow rotation. A single day/night cycle on Mercury lasts 176 Earth days. During the long day, its average temperature can soar to 800°F, while its nighttime average drops dramatically to -290°F, far too cold to support life as we know it.

The primary cause of Mercury’s extreme temperature fluctuations is its lack of an atmosphere. On Earth, the atmosphere shields us from solar radiation and helps keep temperatures from swinging too wildly. Mercury, however, has no such protection. Instead, it has an exosphere composed of oxygen, sodium, hydrogen, and other atoms that have been blasted off its surface by solar wind and meteoroid impacts. Without a cozy atmospheric blanket to trap the heat, Mercury quickly loses the warmth it absorbs during the day.

3. Myth: Venus is Earth’s “sister” planet.

Many people think of Earth and Venus as twins. They’re similar in size and density. Both are rocky planets with valleys, mountains, and volcanoes. Unlike Mercury, both Earth and Venus have atmospheres that trap gases and heat.

But … that’s where the similarities stop. Venus stands apart from Earth in significant ways, such as its toxic mix of atmospheric compounds that trap an immense amount of heat, making Venus the hottest planet in the solar system. Its surface temperature can reach a blistering 900°F. Unlike Earth’s breathable mix of oxygen and nitrogen, Venus’s atmosphere is primarily carbon dioxide, the same gas responsible for global warming on Earth. Instead of clouds made of harmless water vapor, Venus’s clouds are composed of deadly sulfuric acid. The planet’s incredibly thick atmosphere exerts the same pressure as Earth’s oceans at a depth of half a mile.

Additionally, Earth supports life, whereas no life has been discovered on Venus. However, that doesn’t mean scientists are giving up. While the surface of Venus is far too hot for life as we know it, the atmosphere thins and cools as you rise in altitude. About 30 miles above the surface, temperatures range between 86°F and 158°F, and the pressure drops to a level similar to Earth’s surface. This has led some scientists to consider the possibility of extremophile bacteria, like those found in hydrothermal vents or ultra-acidic volcanoes on Earth, living in Venus’s toxic clouds. Some scientists have even spotted mysterious black streaks at the tops of the clouds, which may be caused by iron-rich deposits—or possibly by a microbial form that can endure Venus’s poisonous atmosphere. But for now, this remains just a speculative theory.

3. Myth: Earth is a perfect sphere.

Just because Earth isn’t a perfect sphere doesn’t mean it’s flat. That misconception was disproven well before 1492, when Columbus allegedly proved that you couldn't fall off the edge of the planet. 

Scientific research confirms that Earth is not a perfect sphere. According to the National Oceanic and Atmospheric Administration, Earth is an “irregularly shaped ellipsoid.” It’s about 26 miles wider at the equator than at the poles, due to the centrifugal force created by Earth’s rotation. In simple terms, Earth’s waist is a bit wider than its poles. 

However, that’s only part of the story: Earth’s shape is constantly changing due to geological forces. Floods wear away land. Volcanoes build new land. Earthquakes dramatically reshape the surface. Climate change is also taking a toll on Earth’s geophysics. As Earth’s mass shifts, it impacts the planet’s gravity. For example, Greenland is losing mass rapidly as its ice sheet melts. With less ice pressing down on the bedrock, the ground is rising. A 2020 study revealed that in one part of Greenland, the land has risen nearly 10 feet above sea level since 1900—a significant shift.

Simultaneously, as Greenland loses mass, its gravitational pull weakens. The ocean water that once hugged Greenland’s coast is now moving toward the tropics, increasing the gravitational force in that region. This shift contributes to rising sea levels around islands in the South Pacific, leading to flooding and other challenges for local populations.

4. Myth: Humans have set foot on Mars.

In many ways, Mars resembles a sibling of Earth more than Venus does. Mars is the second-most explored planet, following Earth, with a history of intense study—from ancient Egyptian astronomers to modern robotic rovers and orbiters. Mars is a prime candidate for future human habitation, as space agencies and private firms are investigating it as a potential backup for humanity should Earth no longer be habitable. We've gathered Martian crust samples, examined its atmosphere and seasons, taken pictures of its desolate, reddish landscape, and charted its surface. We've even discovered organic molecules preserved in rocks that are billions of years old. Plus, we’ve even managed to send a helicopter there (although the helicopter’s journey began and ended on Mars itself).

One thing we still haven’t accomplished? Setting foot on Mars. No human has ever walked on the Martian surface, though there is a widespread misconception that astronauts have already done so. According to planetary scientist Bethany Ehlmann from Caltech, the vast knowledge we have of Mars has been gathered through remote observations and sensors placed on the planet, which transmit valuable data back to Earth.

So, with all these impressive robots heading to Mars, could sending humans there really be that hard? As it turns out, yes. There are multiple challenges that make human missions to Mars much more complicated.

First, it’s an incredibly long distance. Even during a phenomenon known as “close approach,” when Earth and Mars are at their closest in their orbits, Mars is still at least 34 million miles away—that’s the theoretical minimum, and the actual distance fluctuates over time. In 2022, for example, the closest approach had us over 50 million miles away. Since both planets travel in elliptical orbits, the distance between them varies, meaning this event occurs only once every 26 months. As a result, the window for launching a mission to Mars is limited to about once every two years.

Second, we lack the technology to ensure astronauts' survival on the journey. A Mars trip currently requires at least 21 months, due to the planets' positions. Starting with the launch window during close approach, it takes about nine months to travel from Earth to Mars. Then, the crew would have to wait three to four months for the planets to align again before beginning the nine-month return trip. Astronauts would need to carry everything necessary for survival: food, water, clothing, oxygen, fuel, scientific tools, building supplies, spare parts, and medical kits. While we could potentially leave some supplies on Mars, getting there remains a massive challenge. Today’s spacecraft simply aren’t equipped to carry that much weight over such a long duration.

Third, we’re still uncertain about how to land a crewed spacecraft on Mars’s thin atmosphere or how astronauts would cope with conditions on the Martian surface. Astronaut Scott Kelly experienced various physiological changes after spending a year aboard the International Space Station, and it's likely that a Martian mission would present even greater challenges. Could the long exposure to the Martian atmosphere cause medical issues? Would the low gravity cause muscles to deteriorate? Would the heart and organs function properly for extended periods? We just don’t know the answers yet.

For all these challenges, humans have yet to set foot on Mars, though research into making that possible is ongoing.

5. Misconception: You can fly a spaceship through Jupiter.

Jupiter is the largest of the planets classified as “gas giants,” which also include Saturn. Unlike the rocky planets like Earth, Jupiter’s mass is largely made up of gases such as hydrogen and helium, with some liquid elements thrown in. But don’t think you can just zoom right through it.

Jupiter’s mass is more than double that of all the other planets combined. Its immense gravity keeps all of its swirling gases and liquids tightly bound in a rapidly rotating sphere. Any spacecraft attempting to pass through would first encounter Jupiter’s thick cloud system, which is about 44 miles deep and consists of frozen ammonia and water ice. These clouds collide with warmer gases from beneath, stirring up intense winds and storms. The Great Red Spot, a colossal storm, has winds that can exceed 400 miles per hour. Good luck getting a spacecraft through that.

Even if you somehow make it through the clouds and reach Jupiter’s inner atmosphere, the conditions aren’t much better. The crushing pressure and rising temperatures turn gases into liquids, creating what NASA refers to as the solar system’s largest ocean. This 25,000-mile-deep ocean of liquid metallic hydrogen conducts electricity and leverages the planet’s rapid rotation to generate an incredibly strong magnetic field. It’s definitely not a place for a leisurely swim.

You wouldn’t even get close to Jupiter’s enigmatic core. This swirling mixture of iron and silicates, which may either be loose and fluid or solid, could reach temperatures as high as 90,000°F.

Nearly everything we know about Jupiter has come from observing it from a distance. Even the one spacecraft we deliberately sent to crash into it—Galileo in 2003—didn’t survive. According to NASA, the probe “penetrated 124 miles into Jupiter’s violent atmosphere before it was crushed, melted, and/or vaporized by the intense pressure and temperature.” Bottom line: your little spaceship trying to fly through Jupiter doesn’t stand a chance.

6. Misconception: Saturn’s rings are solid.

Saturn is the second-largest planet in the solar system and the smaller of the gas giants, but its stunning rings set it apart from its planetary siblings. In 1610, Galileo was the first to spot Saturn’s brilliant rings through a telescope, the same year he discovered Jupiter’s four largest moons. The Dutch astronomer Christiaan Huygens formally described these rings in 1655. However, for the next few centuries, astronomers struggled to understand the true nature and origins of Saturn’s rings, largely because the planet is so far from Earth—an average distance of 900 million miles.

That began to shift in 1979 when NASA sent the first spacecraft to Saturn. By then, scientists had identified Saturn’s primary rings and named them A, B, and C.

Weaker rings were dubbed D and E. (Not the most imaginative names.) The Pioneer 11 probe, Earth’s first visitor to Saturn, uncovered another ring and provided additional insight into their structure. Later, Voyager 1 and 2 captured images revealing that the primary rings are actually made up of thousands of thin, tightly packed ringlets.

In 1997, NASA launched the Cassini spacecraft on a mission to Saturn. After a seven-year journey, it finally arrived and began orbiting the planet, becoming the first spacecraft ever to do so. It sent back remarkably detailed images of Saturn’s rings.

The rings appear as a solid, grooved disk surrounding Saturn, somewhat reminiscent of the close-up image of Voyager’s Golden Record. However, each ring is made up of countless fragments of water ice and rock, remnants of asteroids, comets, or moons that shattered when they collided with Saturn’s gravity. The pieces range in size from tiny grains of sand to massive boulders, with everything in between. Just like a vinyl record, the rings are extremely flat: while the main rings stretch out over 170,000 miles in diameter, they are only 30 feet to half a mile high. The rings vary in density and shape, and some even intertwine with neighboring rings.

But that wasn’t the end of it—Cassini also uncovered unprecedented details about Saturn’s largest moons. It deployed the European Space Agency’s Huygens probe onto Titan’s surface, revealing a landscape carved with mountains and valleys. The spacecraft also found liquid water on Enceladus, expelled from geyser-like features that may be fed by relatively warm underground pools. As if that weren’t enough, it even detected an additional ring around Saturn.

So, Saturn’s rings are far from solid. Despite Cassini running out of fuel and being deliberately flown into Saturn in 2017 (RIP), astronomers continue to make new discoveries from the spacecraft’s two-decade mission.

7. Misconception: Uranus doesn’t stink.

Let’s clear up the jokes now. The planet Uranus—usually pronounced “YUR-a-nus” by scientists—got a rather unfortunate fate when astronomer William Herschel discovered it in 1781. Herschel initially proposed the name Georgium Sidus in honor of the British monarch, George III. However, this name didn’t gain much traction beyond Britain, so astronomers settled on Uranus, named after the Greek god of the sky.

In 1986, Voyager 2 conducted our only fly-by of Uranus. From the data collected by this mission and various telescopes, we’ve learned some fascinating facts. It’s one of the least dense planets in the solar system and one of the two ice giants (the other being Neptune). Uranus is surrounded by several faint rings and has 27 moons. Its mass consists mostly of water and ammonia, encasing a small rocky core that can reach temperatures of 9000°F.

Uranus’s atmosphere tells a different tale: It's a vast, gaseous layer made of hydrogen, helium, and methane. The same gas that cows release also gives Uranus its distinctive aquamarine-blue hue. Adding to that, the planet is filled with clouds of hydrogen sulfide, which gives it its signature scent. It may sound a bit too on the nose, but yes, Uranus truly smells like farts.

In 2018, a team led by Patrick Irwin from Oxford University confirmed the long-discussed composition of these foul clouds by studying how they refracted sunlight. The data pointed to the clouds being composed of hydrogen sulfide molecules, the same substance responsible for the smell of rotten eggs, which seems to dominate the planet’s cold and stormy upper atmosphere.

Luckily, the researchers didn’t have to venture there and take a sniff for themselves. As Irwin pointed out, “Exposure to the -200°C [-328°F] atmosphere made up mostly of hydrogen, helium, and methane would have caused its effects long before the smell could be detected.”

8. Misconception: Neptune and Uranus are the same color.

We don’t know much about Uranus, but we know even less about Neptune, the farthest planet. Voyager 2 flew by Neptune during its 1980s mission. From what we’ve gathered, Neptune has faint rings, a number of moons, and the most violent winds in the solar system, with gusts reaching up to 1200 miles per hour.

Similar to Uranus, Neptune's atmosphere consists of hydrogen, helium, and a bit of methane, which gives it its blue color. However, Neptune has a deeper, cobalt blue tone, in contrast to Uranus's lighter turquoise hue. Scientists have speculated on the cause of this difference, given the planets’ comparable size, mass, and chemical makeup.

Utilizing the same telescopes that helped uncover Uranus’s distinct odor, the Oxford researchers found that Uranus is shrouded in a much thicker methane haze, giving it a whitish appearance. This haze might have been caused by a long-past impact that subdued activity in Uranus’s lower atmosphere. Neptune’s haze is thinner, and it may have formed like snow, allowing the planet’s deeper blue to shine through.

Meanwhile, NASA’s cutting-edge James Webb Space Telescope provided an entirely fresh perspective on Neptune in September. Whereas Voyager 2 captured Neptune as a simple dark blue dot, Webb’s infrared vision revealed it as a brilliant white sphere surrounded by glowing rings. Seven of Neptune’s 14 known moons are visible, with Triton, the largest and most unusual moon, gleaming brightly due to its reflective surface coated in frozen nitrogen. With Webb’s remarkable detail, we can expect to uncover even more about Neptune in the future.

This article was updated in 2023.