The Inner Worlds: Rocky Frontiers

The four planets closest to the Sun are called the “Terrestrial” planets. They are small, dense, and rocky.

1. **Mercury:** The smallest and closest. It looks a lot like our Moon—covered in craters and very dry.
2. **Venus:** Often called Earth’s “Evil Twin.” It is roughly the same size as Earth, but it is covered in thick clouds of acid that trap heat. It is the hottest planet in the system, even hotter than Mercury!
3. **Earth:** Our home. The only place we know of with liquid water on the surface and life.
4. **Mars:** The “Red Planet.” It is about half the size of Earth. It has huge volcanoes, deep canyons, and frozen water at its poles. It is red because its surface is covered in iron oxide—basically rust.

For people starting out in India, Venus and Mars are great targets. Venus is often the brightest “star” in the morning or evening sky, and Mars looks like a bright orange-red dot that doesn’t twinkle.