The inner Solar System is the realm of the rocky planets, Mercury, Venus, Earth and Mars, with the asteroid belt marking its outer edge before Jupiter.
About The inner Solar System
Close to the Sun, where it was too warm for ices to survive while the planets formed, the worlds that grew were small and made of rock and metal. Mercury, Venus, Earth and Mars are the result, each very different: an airless cratered ball, a cloud-wrapped greenhouse, an ocean world and a cold desert.
Beyond Mars lies the main asteroid belt, rubble that never gathered into a planet, held in check by the pull of Jupiter. Despite its reputation the belt is mostly empty space; spacecraft fly through it without having to steer around anything.
What you see in the piece
The piece draws the main-belt asteroids on their real orbits, so the belt appears as a thin haze of moving points. The planets shine only by reflected sunlight and are tiny at this scale.
Questions
What are the inner planets?
Mercury, Venus, Earth and Mars, the rocky planets that orbit inside the asteroid belt.
Is the asteroid belt crowded?
No. The asteroids are spread so thinly that a spacecraft crossing the belt is very unlikely to pass near one.