On Earth, we can get the age of various parts of our planet by finding rocks that contain radioactive atoms. Which other object do we have a good number of rocks from to do this kind of age analysis?

The moon

Explanation:The Moon is an astronomical body orbiting Earth as its only natural satellite. It is the fifth-largest satellite in the Solar System, and by far the largest among planetary satellites relative to the size of the planet that it orbits.

The brightest and largest object in our night sky, the Moon makes Earth a more livable planet by moderating our home planet's wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years.

The Moon is made of rock and metal—just like the Earth and the other rocky planets (Mercury, Venus and Mars). The crust, the Moon's outer shell, is covered by lunar soil, also called regolith: a blanket of fine rock particles, varying between three and 20 metres (10–65 feet) deep.