The closest planet to our sun is shrinking. Here’s what that means - tech.yahoo.com

Telltale wrinkles that cover Mercury, the closest planet to the sun, suggest it was once a larger world that has shrunk in size — and it may be shrinking more than scientists realized. The smallest planet in our solar system is about 36 million miles (58 million kilometers) from the sun on average and completes one orbit around our star every 88 days, according to NASA. The rocky world formed from swirls of gas and dust roughly 4.5 billion years ago. The early days of our solar system were chaotic, marked by violent interactions as a multitude of space rocks orbiting the sun crashed into other objects. Newly formed planets are already hot, much like volcanic lava, but the energy from such collisions generate even more heat. As the heat escapes these worlds over time, the interiors of planets such as Mercury shrink.