The largest planet in the solar system is Jupiter, and the smallest is Mercury.
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Hah, you think I am just going to write some super short answer? Please, that’s just is not my style.
So, let’s start off with the smallest, and one of the coolest planets in my opinion:
Mercury!
Ahh, good ol’ Mercury.
Mercury is the smallest, and innermost planet of our solar system. It is quite similar to our very own Moon, both in looks and surface features. In fact, I like to look at Mercury as the inverted color version of the Moon, because the higher areas of Mercury are darker, and the deep craters are brighter (opposite of our Moon.) Some of these craters, in fact, are so deep, sunlight never reaches parts of those craters. And, in some of those craters, there is actually water ice, just hanging out. This is quite amazing, since the day time temperature on Mercury can reach several hundred degrees Fahrenheit.
Another really cool thing about Mercury is that it has an unusually large iron and nickel core for its size. Scientists think that the core makes up 85% of the planets entire radius. This also makes it the second densest planet, only behind the Earth. Scientists have two different theories as to why the core of Mercury is very large.
The first, and older theory is that Mercury had a collision with another planet when it was first forming, and this blew off most of the silicates and lighter stuff off of baby Mercury and the other planetoid, while also merging the two cores of the planets, making one smaller planet, but with a huge core.
The second, and more exciting theory is that Mercury, a long time ago, used to be a gas giant. But, as it got closer and closer to the sun, more and more of the gas was stripped away from the intense solar winds, until all that was left was a small, metallic core that most gas Giants have. This theory is really cool because it would make our solar system seem a bit more normal, since many other stars have gas giants that orbit really close in to its parent star, but ours does not. It is also a nice feeling to think Mercury used to be a giant once upon a time.
Now, for the largest planet in the Solar System:
Jupiter!
Jupiter is a lot different from Mercury, in almost every way imaginable. First of all, Jupiter is HUGE. Jupiter has a radius of 43,441 miles, compared to tiny Mercury, which only has a radius of 1,516 miles. This means that you could place 28 Mercury-sized planets next to each other, stretch them in a straight line above Jupiter, and Jupiter would still have a larger diameter. Jupiter also has a very thick hydrogen atmosphere, with a cloud layer 30 miles thick, before you reach a point inside Jupiter that is very bizarre.
Once you get past that cloud layer, the hydrogen is so dense now that it takes on a liquid form. But, this isn’t a cold liquid, but is extremely hot, like the molten parts of our planet, only made of hydrogen gas. Past this layer, the hydrogen continues to become more dense to the point it acts like a superheated metal. At this point, anything inside would be burnt beyond recovery, but if you were to send something down there, this is as far as you could get. Below the metallic layer of hydrogen, you have a small rock and ice core (similar to Mercury, actually).
Jupiter has the most moons in the solar system as well, counting 67 so far. Most of these moons are small asteroids that were caught by Jupiter’s immense gravity, but 4 of them, the Galilean moons, are quite unique. The closest one in is Io, which is one of the most volcanically active objects in our solar system, and its surface has a weird mix of colors. Europa has a huge water ocean underneath its thick icy crust, and it is a possible contender to support life because of that. Callisto has one of the oldest surfaces in the solar system, and Ganymede is the largest moon in the solar system, and is bigger than Mercury.
So, there you have it, the largest planet in our solar system, and the smallest, along with some cool details and theories about them. And no, Pluto doesn’t count, it’s classified as a dwarf planet, so leave it at that.