Which category describes the planets that are small, rocky, and have few moons?

• A. Inner
• B. Outer
• C. Comets
• D. Stars

Answer: (A)

Planets that form close to the Sun are generally small and rocky, with solid surfaces. Their gravity is not strong enough to accumulate large atmospheres or many moons, so they end up with only a few natural satellites, if any. In our solar system, this group includes Mercury, Venus, Earth, and Mars. They stand in contrast to the outer planets, which are large gas or ice giants with many moons thanks to more material and stronger gravity farther from the Sun. Comets aren’t planets at all—they’re icy bodies that orbit the Sun and can have tails when they approach it—while stars are enormous luminous bodies, not planets. So the category that describes small, rocky worlds with few moons is the inner planets.