The inner solar system is the name of the terrestrial planets and asteroid belt. Terrestrial is just a fancy way of saying rocky. Like the Earth, terrestrial planets have a core of iron and rock.
At the center of the solar system is the Sun. The Sun is a big ball of hydrogen powered by nuclear reactions. Massive explosions are going on all of the time inside the Sun. It’s what makes the light every day and keeps our planet warm. Light zips from the Sun to us in about eight minutes. The Sun is the most massive thing in our solar system. It is so big you could fit about a million Earths inside of it!
Closest to the Sun is the planet Mercury. You could squeeze about eighteen Mercury’s inside of Earth. It is made of mostly rock, but it has a huge iron core and it generates a big magnetic field. Speedy little Mercury sails around the sun in only eighty-eight days. Mercury was the messenger of the gods in Roman mythology, known for his speed.
Second in line comes Venus, which is sometimes called Earth's twin. It's about the same size as Earth, but that’s where the similarities end. Venus is always covered in thick clouds full of sulfuric acid. They whip around the planet at more than two hundred twenty mph. Violent winds shoot sand made of silicate around Venus’s very dry, arid surface. The temperature averages nine hundred degrees, and the pressure’s ninety times that on Earth. It takes two hundred and twenty four days to orbit the sun. Like Mercury, Venus was also named after a Roman Goddess, the Goddess of love.