Teacher: Mercury is the second smallest planet and the closest to the sun. It was named after a Roman god, the fleet-footed messenger. 
Students: Why do people call it “fleet footed messenger”?
Teacher: Because it seemed to move more quickly than any other planet. But it has a diameter that is 40 percent smaller than the Earth's, and 40 percent larger than the Moon's.
Students: Does the surface of Mercury like the Earth or the Moon? 
Teacher: If you were to step onto the surface of Mercury, you would find a world like the moon. Mercury's surface looks like one big chocolate chip cookie with craters dotting the surface. An explorer would notice that the Sun appears two and a half times larger from Mercury than it does from Earth.
Students: Does Mercury also have days and nights like the Earth?
Teacher: In Mercury, the sky is always black because it has almost no atmosphere to cause light to scatter.