* Earth's Active Geology: Earth is a very geologically active planet. Plate tectonics constantly recycles the Earth's crust, causing rocks to melt, reform, and erode. This means that most of the oldest rocks on Earth have been destroyed or heavily altered over time.
* Lunar Surface: The moon, in contrast, lacks plate tectonics and has a much less active geological history. This means the lunar surface has remained relatively undisturbed for billions of years.
* Age Comparison: While some Earth rocks are very old, the oldest rocks on Earth are about 4 billion years old. Lunar rocks, however, have been found to be up to 4.5 billion years old. This is closer to the estimated age of the solar system itself.
So, the rocks brought back from the moon are not older than *all* rocks found on Earth, but they are older than the vast majority of them. They offer a unique window into the early history of our solar system.
