What is the primary role of finding geological units with known ages (e.g., Apollo landing sites) when dating impact history?

Answer

To establish a benchmark density value for estimating the age of other surfaces

These known-age sites provide the anchor points that scientists use to build the absolute age scale curve, linking a measured crater density value to a specific calendar age.

What is the primary role of finding geological units with known ages (e.g., Apollo landing sites) when dating impact history?
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