Up next in 10
Have humans set foot on Mars? Are Jupiter's rings made of solid ice and rock? Does Uranus really smell like ... well, you know?
Join host Justin Dodd (@juddtoday) as he breaks down some common myths and misconceptions about the eight (or nine if you're cool) planets in our solar system.
00:00:00 Pluto
00:02:13 Mercury
00:03:30 Venus
00:05:19 Earth
00:06:58 Mars
00:10:15 Jupiter
00:12:14 Saturn
00:14:52 Uranus
00:16:52 Neptune
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2025 Mental Floss
1 Misconception About Each Planet | Mental Floss
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0:00
Poor Pluto. For 76 years, it occupied the coveted spot as the ninth planet in our solar system
0:06
Growing up, I learned it was the farthest planet from the sun. A mysterious celestial body whose diameter is about the distance between New York and Houston
0:14
with an average temperature of minus 387 degrees Fahrenheit. The lord of five moons
0:20
The only planet named by an 11-year-old girl. Pluto had a lot going for it
0:24
But in 2006, it was knocked off its planetary pedestal by some jerks
0:28
I mean, astronomer jerks at the International Astronomical Union. So, no, Pluto doesn't count as one of the nine planets in our solar system
0:37
But it wasn't as cut and dried a decision as you might imagine. Hi, I'm Justin Dodd, and I'll get into that along with one misconception about each of
0:45
the still-recognized planets in the solar system in today's episode of Misconceptions
0:49
We'll discuss the potential of life on Venus and Uranus' unique odor
0:54
Spoiler alert, neither are great. Let's get started. According to the International Astronomical Union
1:08
a celestial body has to meet three criteria to be considered a fully recognized planet in our solar system
1:14
One, it has to orbit the sun, which Pluto definitely does. Two, it has to be roughly spherical
1:21
Check. And three, it has to be the most gravitationally dominant object in its orbit
1:26
clearing the area of similarly sized objects with a few agreed upon exceptions
1:31
That's where Pluto fails the test. It still shares some turf with other large objects in the Kuiper Belt
1:36
which means it hasn't cleared its orbital area. The union voted to recategorize Pluto as a dwarf planet
1:42
But the move was super controversial. Less than 5% of the world's astronomers took part in the vote
1:48
and many others disagreed with the International Astronomical Union's criteria. There was a major public outcry
1:53
Adults who had grown up learning about the nine familiar planets were confused and upset
1:59
What is my very educated mother going to have just served us now? Many respected scientists remain convinced that Pluto should be a planet due to its size
2:07
shape, and orbit, no matter what the eggheads at the IAU think. People have strong opinions about Pluto
2:13
Mercury is the hottest planet. Tiny, rocky Mercury is the closest planet to the sun and the smallest in the whole solar system
2:21
not counting Pluto. You see how this is confusing? It has an oval-shaped orbit that brings it as near as 29 million miles to the sun and up to 43 million miles away from it
2:31
But even at that relatively close proximity, it's still not the hottest planet
2:35
Mercury turns on its axis pretty slowly. Each full day-night cycle on Mercury takes 176 Earth days
2:43
Its average temperature during a long daytime can reach a toasty 800 degrees Fahrenheit
2:48
Its nighttime average plunges to minus 290 degrees Fahrenheit, which is far too cold to sustain life, as far as we know
2:55
The main reason for the big swing in temps is Mercury's lack of atmosphere
2:59
On Earth, the atmosphere protects us from solar radiation and insulates the planet from extreme temperature variations
3:06
Mercury has none of these perks. Instead, it has an exosphere of oxygen, sodium, hydrogen, and other atoms
3:12
that have been scoured off Mercury's surface by blasts of solar wind and meteoroid impacts
3:18
With no cozy atmospheric blanket to trap heat, Mercury loses the warmth it absorbs during its days
3:23
So, if Mercury isn't the hottest planet, which one is? We're getting to that
3:28
Hold your horses there, cowboy. Venus is Earth's sister planet. People often think of Earth and Venus as twinsies
3:36
They're roughly the same size and density. They're both rocky planets featuring valleys, mountains, and volcanoes
3:42
Unlike Mercury, both Earth and Venus have atmospheres that trap gases and heat
3:46
But that's about where the similarities end. Venus differs from Earth in some major ways, like in its toxic cocktail of atmospheric compounds
3:55
which retain tons of heat to make Venus the hottest planet in the solar system
3:59
Its surface temp can reach a scorching 900 degrees Fahrenheit. Instead of Earth's breathable blend of oxygen and nitrogen, Venus's air is primarily carbon dioxide
4:09
the same stuff causing global warming on our own planet. Instead of our clouds of harmless water, Venus' clouds are made of deadly sulfuric acid
4:17
The planet's incredibly dense atmosphere exerts the same amount of pressure as Earth's oceans at a depth of half a mile
4:24
Plus, Earth supports life, while nothing living has been found on Venus
4:28
That doesn't mean scientists aren't looking. While the surface of Venus is way too hot to accommodate life as we know it
4:34
the planet atmosphere actually thins and cools as altitude increases as Aaron discussed in our video covering 100 facts about the planet 30 miles above the surface of Venus temperatures vary between 86 and 158 degrees Fahrenheit and the pressure relents to about the same level found on the
4:50
Earth's surface. That leads some scientists to consider the possibility of extremophile
4:55
bacteria, like those found in hydrothermal vents or ultra-acidic volcanoes on Earth
4:59
living in Venus's poisonous clouds. Scientists have even detected some mysterious black streaks
5:05
at the tops of the clouds, which may be caused by iron-rich deposits or perhaps by an as-yet
5:10
undiscovered microbial form with the chemical makeup that can withstand Venus's toxic atmosphere
5:17
But for now, it's only a speculative theory. Earth is a sphere
5:22
Whoa, whoa, whoa, whoa. We are not saying that just because Earth isn't perfectly round that it's
5:26
actually flat. That idea got debunked even earlier than 1492, when Columbus supposedly
5:32
proved to the haters that you couldn't sail off the edge of the planet. We are merely relaying
5:36
the scientific evidence showing that Earth is not a perfectly round sphere. According to the
5:41
National Oceanic and Atmospheric Administration, Earth is an irregularly shaped ellipsoid. It's
5:46
about 26 miles wider in diameter at the equator than it is at the poles due to the centrifugal
5:52
force generated by Earth spinning on its axis. Basically, it's fatter around the middle
5:56
But that's not the whole story. Earth's shape is constantly changing topographically
6:01
Floods erode land. Volcanoes create new land. Earthquakes can alter the land in dramatic
6:05
ways. And climate change is having a huge impact on our planet's geophysics. When Earth's
6:11
mass shifts from one place to another, it affects the planet's gravitational forces
6:15
Here's an example. Greenland is losing mass rapidly because its ice sheet is melting
6:20
The remaining ice sheet doesn't press down on the bedrock of Greenland as much because
6:24
it weighs less, so the ground is actually rising. A 2020 paper reported that at one place in Greenland, the land had risen roughly 10 feet
6:32
above relative sea level since 1900, which is, like, a huge, scary amount
6:37
I say relative sea level because, at the same time, since Greenland is losing mass, it's
6:41
also losing gravitational force. The ocean volume that used to hug Greenland's shores is drifting to the tropics instead
6:49
increasing that region's gravitational force. You can see it in the rising seas around islands in the South Pacific Ocean
6:55
which leads to flooding and other problems for residents. People have landed on Mars
7:00
In some ways, Mars is more of a sibling planet to Earth than Venus is
7:04
No other planet besides Earth has been scrutinized as much as Mars
7:09
from the work of ancient Egyptian astronomers to today's robotic rovers and orbiters
7:14
Space agencies and private companies are focusing on Mars as a potential abode for humanity
7:18
if or when Earth becomes uninhabitable. We've collected samples of Mars's crust
7:24
studied its atmosphere and seasons, taken photos of its eerily rusty landscape
7:29
and mapped its surface. We've discovered organic molecules buried deep in billion-year-old Martian
7:34
rocks. We've even flown a helicopter there. But to be clear, I don't mean two Mars trips started
7:39
and ended on the Red Planet. But one thing we have not done is actually go to Mars. No human
7:45
has ever landed on the Red Planet. Though, according to Caltech planetary scientist Bethany
7:50
Ellman, one of the most common misconceptions is that astronauts have done so. In fact
7:55
we've gained our vast knowledge about Mars by observing it from afar or by monitoring it
7:59
with sensors on the planet that beam information back to Earth. So if we're sending all these
8:04
awesome robots to Mars, could sending actual people really be that difficult? As it turns out
8:10
yeah, there are a few reasons why. One, it's super far. When Earth and Mars are at the nearest points in their orbits to each other
8:17
a phenomenon called close approach, Mars is still at least about 34 million miles away
8:23
And that's the absolute theoretical minimum, given fluctuations over time. In 2022, the close approach actually left us over 50 million miles away
8:32
Because the planet's orbits are elliptical and the distance between them varies
8:35
close approach doesn't happen very often, usually about every 26 months. That means the optimal
8:41
window for successfully launching a spacecraft to Mars is limited to roughly once every two years
8:47
Two, we don't have the technology to keep an astronaut alive during the journey. Any trip to
8:51
Mars currently requires a minimum of 21 months due to the positioning of the planets during the
8:56
journey. Beginning with the launch window near close approach, it would take nine months to fly
9:01
from Earth to Mars. Then the crew would need to spend three to four months waiting for the
9:06
planets to align for the nine-month return trip. The crew would need to bring every single
9:11
thing for sustaining life with them Food water clothing oxygen fuel plus scientific instruments building materials spare parts medical supplies a DVD player Parks and Rec seasons 2 to 4 on DVD the DVD player remote spare batteries for the remote the list goes on and on And while we might be able to drop off some of
9:29
those supplies on Mars, there's still the whole getting there thing. Today's spacecrafts
9:34
don't have the ability to carry all that weight for so long. Three. Nobody knows exactly how to land a crewed spacecraft in Mars' thin atmosphere
9:41
or how astronauts would fare on the Red Planet. Astronaut Scott Kelly experienced several physiological changes
9:47
after spending one year aboard the International Space Station, and it's likely that any Martian voyager would experience worse
9:54
Would the long-term exposure to the Martian atmosphere cause medical problems? Would the relative lack of gravity cause muscles to turn to jello
10:02
Would one's heart and organs continue to function over such long periods
10:07
I mean, maybe. We just don't know. For all these reasons and more, humans have never been to Mars, but research into the possibility continues
10:15
You can fly a spaceship through Jupiter. Jupiter is the larger of what astronomers call the gas giants, which also includes Saturn
10:23
Unlike the four rocky planets we've already mentioned in this video, the gas giant's mass is primarily, well, what we think of as gases, such as hydrogen and helium, along with some liquids
10:34
But that doesn't mean you can just zoom right through it. Jupiter's mass is more than twice that of all the other planets put together. Gravity holds all of
10:41
the swirling matter together in a rapidly rotating ball. Any spacecraft attempting a fly-through
10:46
would first meet the three layers of Jupiter's cloud system, which is about 44 miles thick and
10:52
contains a mix of frozen ammonia and water ice. The clouds collide with warmer gases rising from
10:57
Jupiter's interior, creating powerful winds and storms. The Great Red Spot is a monster storm
11:02
with winds topping 400 miles per hour. Try getting a command module through that
11:07
But let's say you make it past the cloud layer and enter Jupiter's inner atmosphere
11:12
Crushing pressure and skyrocketing temperatures turn gases into liquids and form what NASA calls
11:17
the solar system's largest ocean. The 25,000-mile-deep pool of liquid metallic hydrogen
11:23
can conduct electricity. It also uses the planet's fast rotation to generate an immensely
11:28
strong magnetic field. I mean, it's no sea of tranquility. Finally, you won't even get close
11:34
to Jupiter's mysterious core. This roiling mix of iron and silicates, which could be either a
11:39
stew of loose matter or a solid form, may reach 90,000 degrees Fahrenheit. Pretty much everything
11:45
we've learned about Jupiter, we've gleaned by observing it from afar. And the one craft we
11:50
deliberately crashed into it, Galileo, in 2003, didn't emerge from the other side. As NASA says
11:56
the probe penetrated 124 miles into Jupiter's violent atmosphere before it was crushed
12:03
melted, and or vaporized by the intense pressure and temperature. The bottom line? Your puny
12:08
spaceship on its way through Jupiter is not going to make it, so our advice? Take a scenic detour
12:15
Saturn's rings are solid. Saturn is the second largest planet in the solar system as well as the
12:21
smaller gas giant, but its rings instantly set it apart from its planetary neighbors
12:26
Galileo observed Saturn's bright rings through a telescope in 1610, the same year he discovered
12:31
Jupiter's four largest moons. The Dutch astronomer Christian Huygens formally described the rings
12:37
in 1655. Over the following four centuries, though, astronomers struggled to understand
12:42
the rings' composition and origins, mainly because Saturn is so far away from Earth
12:47
an average of 900 million miles away. That began to change in 1979
12:51
when NASA sent the first spacecraft to Saturn. By that time, scientists had observed Saturn's main rings
12:56
and dubbed them A, B, and C. No points for creativity there
13:01
Fainter rings were dubbed, wait for it, D and E. I mean, come on, astronomers had like 400 years
13:06
to come up with better names for these things, and this is what they're going with? It's shameful
13:10
The space probe Pioneer 11, Earth's first visitor to Saturn, discovered another ring along with other clues
13:16
to their makeup. Then, Voyager 1 and 2 captured images showing that the main rings are actually thousands
13:22
of thin ringlets. In 1997, NASA launched the Cassini Orbiter on a mission to Saturn
13:27
It took about seven years to get there. Once it arrived, it began orbiting the planet, the first spacecraft to ever do that, and
13:34
beaming back incredibly detailed images of the planet's rings. They do resemble a solid, grooved plane surrounding the planet, like a close-up of Voyager's
13:42
golden record. But each ring is composed of countless fragments of water, ice, and rock
13:48
The remains of asteroids, comets, or moons that broke up when they came into contact
13:52
with Saturn gravity Some of the pieces are as tiny as grains of sand Some are the size of mountains and the rest fall somewhere in between And like a vinyl LP the rings are super flat The main rings are 170 miles in diameter
14:06
but only 30 feet to a half mile in height. They vary in density, in shape, and some rings
14:12
intertwine with their neighbors. But that wasn't all. Cassini also captured never-before-seen
14:16
details about Saturn's largest moons. It deployed the European Space Agency's Huygens probe to the
14:22
surface of Titan, revealing topography carved into mountains and valleys. It also discovered
14:27
liquid water on Enceladus, ejected from geyser-like formations possibly fed by relatively warm pools
14:33
of water below the moon's surface. It even discovered another ring around Saturn. So Saturn's
14:39
rings are anything but solid. And even though Cassini ran low on fuel and was intentionally
14:44
flown into Saturn itself in 2017, RIP my guy, astronomers are still making discoveries from
14:50
its 20-year mission. Uranus doesn't stink. Okay, okay, okay, let's just get the jokes out of the
14:57
way right now. The planet Uranus, generally pronounced Uranus in scientific circles
15:01
really got the short end of the stick when astronomer William Herschel discovered it in 1781. Herschel initially wanted to name it Georgium Citus after the reigning monarch George
15:10
III, but that wasn't too popular outside of Great Britain, so astronomers agreed on Uranus instead
15:16
The name honors the Greek god of the sky, but for generations of kids, it's basically the planetary version of Seymour Butts
15:23
Voyager 2 conducted our only flyby of Uranus back in 1986. From the data collected by Voyager 2 and a variety of telescopes, we've learned a few key facts
15:32
It's one of the least dense planets in the solar system and one of two ice giants
15:37
The other one is Neptune. It has several faint rings and 27 moons
15:41
Uranus' mass is mostly water and ammonia surrounding a tiny rocky core that can reach
15:46
9,000 degrees Fahrenheit. Uranus' atmosphere is a different story. It's a big gassy blanket
15:52
of hydrogen, helium, and methane. Yeah, the same gas that cows expel also gives Uranus
15:59
its aquamarine blue color. On top of that, the planet supports clouds of hydrogen sulfide
16:04
which is responsible for its signature scent. Yeah, seems a little on the nose, but Uranus
16:09
It really does smell like farts. In 2018, a team led by a researcher
16:13
from the University of Oxford confirmed the long debated composition of these odiferous clouds
16:19
by yzing the way they refracted sunlight. The data suggested the clouds were made up
16:23
of molecules of hydrogen sulfide, the same compound that makes rotten eggs stink
16:28
which seemed to pervade the planet's cold and windy upper atmosphere. Fortunately, the scientists didn't have to actually go there
16:34
and take a sniff for themselves. As Professor Patrick Irwin, The Oxford researcher we alluded to earlier said
16:41
"...suffocation and exposure in the negative 200 degrees Celsius minus 328 degrees Fahrenheit atmosphere
16:47
made of mostly hydrogen, helium, and methane, would take its toll long before the smell.
16:52
Neptune and Uranus are the same color. We do not know a lot about Uranus, but we know even less about Neptune, the outermost planet
17:02
Voyager 2 flew by Neptune on its 1980s mission. We know that the planet has faint rings, several moons, and the windiest atmosphere in the solar system
17:10
with gusts blasting up to 1,200 miles per hour. Like Uranus, Neptune has an atmosphere composed of hydrogen, helium, and a smidgen of methane
17:17
which makes it appear blue. But Neptune is a deeper cobalt blue, contrasting with Uranus's light turquoise blue
17:24
Scientists have wondered what the differentiating factor could be, since their size, mass, chemical composition are so similar
17:31
Using the same telescopes that help them uncover Uranus's smell, the Oxford researchers discovered that Uranus is enveloped in a much thicker
17:39
obscuring layer of methane haze, which appears whitish. It might be the result of a long-ago
17:44
impact that quieted the activity in Uranus' lower atmosphere. Neptune's haze layer is thinner and
17:50
may have precipitated like snow, revealing its deeper blue hue. On the other hand, NASA's new
17:55
James Webb Space Telescope gave us an entirely new view of Neptune last September. Whereas Voyager
18:01
2 pictured Neptune as a dark blue dot, Webb's infrared telescope showed it as a dazzling
18:06
white orb circled with glowing rings. Seven of Neptune's 14 known moons appear. Triton
18:12
its largest and strangest moon, shines like a bright star thanks to its reflective
18:17
frozen nitrogen-covered surface. With Webb's ability to capture unprecedented detail, we will surely learn more about Neptune in the years to come
18:25
That's all the time we have for the eight, or nine if you're chill, planets in our solar system. I hope you feel a little bit closer to the majesty of space
18:34
Except maybe not Uranus. I feel like I can smell it from here. Thanks for watching. We'll see you next time
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