(SciShow Kids intro)
Jessi: Hi guys! Welcome back to the fort! Today, Squeaks and I thought we'd do a little sightseeing using our telescope. We're gonna tour our Solar System.

The Solar System is made up of the Sun, the Earth, and seven other planets, plus lots of dust, big rocks, gas, and other stuff. All of that stuff together is in orbit around the Sun, traveling around it over and over.

And the Solar System is huge! It's so huge that only one space craft so far has ever flown from the Earth all the way to the edge of the Solar System. It's called Voyager 1. It's a probe about the size of a small car but doesn't have any people in it. It has flown from Earth through the Solar System taking pictures of lots of the planets as it went, and it took over 35 years to reach the edge. It's so big, that today we're just gonna cover half of it. And keep in mind it took Voyager 1 all that time to fly from Earth, and Earth isn't even at the middle of our Solar System. The Sun is. So let's start there, right at the center of the action.

The Sun is a star, and like most stars, it's a huge ball of super hot gas that gives off light and heat. Without the Sun, Earth would be a dark, frozen world with no life. But Earth isn't the closest planet to the Sun. That would be Mercury.

Not only is Mercury the closes planet to the Sun, it's also the smallest. It's less than half the size of the Earth. Mercury doesn't have a lot of gases around it like Earth does. Without these gases to hold in heat, Mercury has the biggest changes in temperature of any of the planets. It can go from a super chilly 170 degrees below zero at night to a very warm 425 degrees Celsius during the day. People couldn't survive on Mercury, and I don't think robotic rats could either.
And things get even more extreme on Venus, the next closest planet to the sun.

Venus is the brightest planet in our solar system. If you know where to look you can sometimes spot it from Earth, especially just after the sun sets at night or just before when it rises in the morning. We've sent probes to Venus to take pictures too. They show us that the planet is rocky and covered with clouds, but doesn't have any life on it because Venus is extremely hot. In fact, even though it's not the closest to the sun, Venus is the hottest planet in our solar system with temperatures reaching as high as 460 degrees Celsius (460*C). Wooo... let's cool off and head to the next planet.

Hey, this place looks familiar! Welcome back to Earth. Earth is about 93 million miles from the sun, and it takes 365 days-- our year-- for the Earth to orbit the sun. And Earth is unlike any other planet in our solar system, for at least two reasons. Number one: it's the only planet that we know for sure has liquid water on its surface. And number two: it's the only planet that we know has life on it. No other planet in the solar system has plants or animals or any living things on them. Earth, you rock.
Now let's move on to our last stop for today. It's time for a mission to Mars.

Mars's nickname is 'the red planet'. That's because Mars has a lot of minerals on its surface that give it a unique reddish color. Mars is sort of similar to the planet that we live on: the length of a day on Mars is almost the same as a day on Earth, it's just about forty minutes longer. And Mars even has some ice on it, frozen at its north pole. But as far as we know there's no liquid water anywhere on Mars because it's so cold. Mars also has mountains and canyons like Earth; in fact it's home to the solar system's biggest volcano. Scientists have named it Olympus Mons, and it's nearly three times larger than Mount Everest the tallest mountain on Earth.

Clearly the solar system is an amazing place, full of different worlds with all kinds of extreme environments. And we've only covered four planets so far! Those four planets all have one thing in common: they're all solid worlds with hard, rocky surfaces that, if you ever went there, you could stand on. Mercury, Venus, Earth, and Mars are what we call 'rocky planets'.

But next time we're going to tour planets with no surface at all, the gas giants.
Until next time, thanks for exploring with us. And remember, if you have a question for SciShow Kids let us know by leaving a comment or emailing us at kids@scishow.com .
Thanks guys!