Temperatures at the dark craters of the north pole of Mercury can dip to
as low as 370 degrees below zero.
Image: NASA/Johns Hopkins University Applied Physics Lab/Carnegie Institution of Washington
There's Ice in Mercury
Of all the planets in the Solar System, Mercury is the closest to the sun. You'd naturally think that it's also the hottest, but it's not (that distinction belongs to Venus). Oh, no doubt Mercury can get quite hot - its surface temperature can reach up to 800 °F, but at the poles, its temperature never gets above freezing. That's where NASA's Messenger Spacecraft found a large volume of water ice - estimated to be 100 billion to 1 trillion tons of ice, actually.
Maat Mons, the highest volcano on Venus. Image: NASA/JPL
It Snows Metal on Venus
Snowcapped mountains on Earth are majestic, but they're by no means unique in our Solar System. Venus has its own snowcapped mountains, but instead of water, the "snow" is made of heavy metals like lead sulfide (galena) and bismuth sulfide (bismuthinite).
Olympus Mons on Mars. Image: NASA/JPL
Mars has the Tallest Mountain in the Entire Solar System
Let's skip Earth for now and head on over to Mars. If you think our Mount Everest is tall, check out the Olympus Mons on the Red Planet. At about 14 miles (22 km) tall, it's three times as tall as Mount Everest's height above sea level. It's pretty big, too. Olympus Mons is approximately the size of Arizona.
Jupiter's Great Red Spot, as "spotted" by Voyager 1 in 1979. Image: NASA/JPL/CalTech
Jupiter's Great Red Spot
The Great Red Spot on Jupiter is a storm that has been raging for at least 400 years. It was large enough to be seen from Earth (it first spotted by Giovanni Cassini in the late 1600s with a primitive telescope). In fact, the Great Red Spot was large enough to engulf three Earths, though its size has decreased over the past hundred years.
If you think that storms on Jupiter are quite violent, you'd be right: winds around the edge of the Great Red Spot peak at over 260 mph, with lightning bolts* 10 times as powerful as anything ever recorded on Earth.
*Unlike on Earth, lightning bolts in the gas giant Jupiter don't strike the ground. They're cloud to cloud.
Simulated image of Saturn's rings, with false colors to represent ring particle sizes in different regions based on radio signals. Image: NASA/JPL
Saturn's Magnificent Rings and Hexagon Cloud
Why does Saturn have a ring? Because Neptune proposed and they're now married, goes the joke. Ask any schoolchildren and they'd tell you that Saturn has magnificent rings. These rings were first observed by Galileo back in 1610 though his telescope wasn't good enough to discern the actual structure (he thought that Saturn had "ears."). Some forty years later, Christiaan Huygens suggested that Saturn was surrounded rings.
The rings of Saturn are made of countless small particles - from dust particles to large rocks, mostly made of water ice with trace silica material - that orbit the planet. The rings aren't solid - there are thousands of gaps, ringlets, and spiral waves in the rings that are caused by their interactions with the moons of Saturn.
Color-composite image of Saturn's northern hexagon, as taken by the Cassini spacecraft.
Image: NASA/JPL/SSI/Jason Major)
If you thought that the rings are awesome, check out Saturn's Hexagon. It's a strange hexagonal cloud pattern in the north pole of the planet. Each side of the hexagon is about 8,600 miles long (which is longer than the Earth's diameter)
Oh, one more neat fact about Saturn: since it's made mostly of hydrogen and some helium, it's the least dense of all the planets. In fact, it's less dense than water so if you have a bathtub big enough to fit Saturn, the whole planet will float.
Uranus orbits on its side, with its rotational axis nearly perpendicular to the Sun.
Image: Lawrence Sromovsky/University of Wisconsin-Madison/Keck Observatory.
Uranus, the Sideway Planet
Uranus is the only planet that has an axis of rotation approximately parallel with the plane of the Solar System - this means that the gas giant rotates on its side. The cause of this unusual tilt is unknown, but scientists think that during the formation of the Solar System, an Earth-sized protoplanet (or a series of protoplanets) smashed into Uranus, pushing the planet over on its side.
The Great Dark Spot of Neptune, as captured by Voyager 2 in 1989.
Image: NASA/Voyager 2 Team
Neptune's Supersonic Great Dark Spot
Like Jupiter's Great Red Spot, there are large storms on Neptune - the largest of which is named the Great Dark Spot. The elliptical spot is largely the same size as Earth, and it has the fastest winds in the Solar System. Neptune's winds have been clocked at over 1,500 mph - that's twice the speed of sound.
Earth, the Goldilocks Planet
So, you've read 7 wonderful things about the planets of our solar system, but what about our own? What's so special about the third rock from the Sun, our home planet Earth?
Well, it's unique because it's the only planet we know of that has life. Doubly unique because it has intelligent life - though that's arguable depending with whom you talk to ;)
Other planets in the Solar System have liquid water, plate tectonics, and atmosphere - but only Earth has them all just right. It's not too hot or too cold, and it's neither too wet nor too dry for life.
That made Earth a unique planet in the Solar System, but what about in the Universe? In 2011, the Kepler Space Observatory Mission team released a list of 1,235 candidate extrasolar planets, with 54 that rotate around "circumstellar habitable zone" - an astronomical comfort zone, if you will, that allow liquid water to exist.
As of 2013, the list has expanded to 3,216 candidate and 132 confirmed exoplanets in 76 stellar systems. In our Milky Way galaxy alone, astronomers estimated that there are at least 17 billion Earth-sized exoplanets (what about other galaxies in the Universe? It's been estimated that there are as many as 500 billion galaxies in the entire Universe, so you do the math).
But is there life on other planets? Let us leave you with this quote from the 1997 movie Contact, where the father of a young Ellie Arroway replied to his daughter's question:
Young Ellie Arroway: Dad, do you think there's people on other planets?
Theodore Arroway: I don't know, Sparks. But I guess I'd say if it is just us ... seems like an awful waste of space.