How did scientists determine the solar system's age around 4.57 billion years?

• A. Dating meteorite material dating back to ~4.57 billion years
• B. Dating rocks on Earth's surface only
• C. Counting lunar craters
• D. Measuring solar wind speed

Answer: (A)

Estimating the solar system’s age relies on radiometric dating of the oldest solid material we can find. Meteorites contain primitive components that formed at the very beginning of the solar nebula, before planets fully condensed. By measuring radioactive-to-stable isotope ratios in these materials with precision instruments, scientists can determine when those minerals crystallized. The uranium–lead dating method, used on calcium-aluminum-rich inclusions and other primitive meteorite components, gives ages around 4.56 to 4.57 billion years. Those ages cluster together, pointing to the time when the solar system formed.

Rocks on Earth have been recycled and altered through tectonics and melting, so their ages don’t reliably mark the solar system’s birth. Counting lunar craters provides a history of surface impacts, not an absolute age for the solar system. Measuring solar wind speed tells us about current solar activity, not how long the system has existed. Hence, dating the oldest meteorite material with radiometric clocks gives the best estimate of about 4.57 billion years.