Class, today if you will listen, We'll learn the planets in the solar system. Every planet in its right place, From our star the Sun out to interstellar space. Yeah, yeah, planets and moons, asteroids and comets all fit the tune. The very first planet next to the Sun Is Mercury. It's the only one Without a trace of atmosphere. Its surface is a cratered sphere. Each crater punched by an planetesimal From great big ones to the infinitesimal. It has no moon, and the way it's spun, Is to make three turns for every two around the Sun. So slow a spin is sure to yield. Only a bit of magnetic field. The next planet out is the goddess of love, Venus, the name, and just above The horizon at dusk, but not too far, Is the place to see it as the evening star. About the same as the Earth in size, It's a planet shrouded by cloudy skies Which block our view of its surface layer But radar let's us look in there. The atmosphere's of CO2 Which lets the visible Sunlight through, But traps the heat. Yes, that's correct; It makes a super greenhouse effect. Because of that its temp is tops. Its clouds are sulfuric acid drops. With the old volcano, Mount Maxwell, Venus resembles a heavenly hell. Next planet out is our own Earth. I hope by now you can see its worth. As a place that's safe for me and you. With its air of nitrogen and O2. We keep on moving out in space And next find Mars as a landing place. CO2's in the atmosphere there Very cold, and very rare. The surface has canyons, craters and dunes, Volcanic peaks, two tiny moons, Polar caps (dry ice and snow), Dust storms when the Martian winds blow. Red in the sky, like the god of war. Half the size of Earth, and one thing more, Like all the inner planets, it has an iron core. Getting far from the Sun where the ice won't melt, We pass across the asteroid belt. Then on to Jupiter, biggest of them all: Its a methane, hydrogen, helium ball. Bigger than the Earth by a factor of ten, Its mass is 300 times again. That of our little rocky sphere. But better to be little than be landed there. If you dropped down into a Jupiter cloud, Though the colors of the belt are very loud, The gases would send you to a grave yard plot, Especially those in the great red spot. If you name the moons you'll find the list goes Io, Europa, Ganymede, Callisto. They're the biggest, almost size of Mercury, Discovered long ago by Galileo Galile. Jupiter also has a tiny ring, But if you want to see the real thing, Go twice as far before your stop, And onto giant Saturn let yourself drop. A lot like Jup in size and composition, It carries on the mythologic tradition. Jupiter was the gods' own king. Saturn was a Harvest God with sickles for his ring. Alike in size, for what their worth, Are Uranus and Neptune, four times bigger than the Earth. Hydrogen and water with a rocky core that's hot, These two planets the ancients didn't spot. Uranus spins tipped over on its side. It has rings, but not so wide As those on its bigger planetary brother, While its odd rotation makes it have odd weather. Neptune and Uranus look real blue 'cause methane grabs the red light coming through. Methane's also all there is to see On tiny Pluto which is also icy. Moving out from Neptune, far from the Sun. Pluto, with Charon, is the last found one Of the solar system planets that we know. So out to the comet cloud we go. It's forty thousand AU to the vast Oort Cloud The name of the place where the comets crowd. Passing stars make them drop in toward the Sun And Halley's Comet is the best known one. If more than one hundred times they pass The Sun they evaporate and boil away to gas. They leave behind a wake of tiny dust For the meteor shower you see in mid-August. There's lots more to see past the planets, my friend, But of this silly verse we have finally reached the end. We need to rap 'bout stars sometime, But it's hard work thinking up a Sirius rhyme.