Chinese space agency-launched Chang’e-5 lunar probe just returned the moon’s first fresh samples of rock and debris in more than 40 years.

Now, an international team of scientists – including a Washington University in St. Louis expert – has assessed the age of these moon rocks to be close to 1.97 billion years old.

The age determination is one of the first scientific findings from the Chang’e-5 mission, which successfully collected and returned to Earth rocks from some of the moon’s youngest volcanic regions.

All of Apollo’s volcanic rocks were older than 3 billion years. Additionally, all of the youthful impact craters whose ages have been estimated by sample analysis are less than 1 billion years old. Thus, the Chang’e-5 samples fill an important gap.

The gap that, according to researchers, is important not only for studying the moon, but also for studying other rocky planets in the solar system.

The moon is approximately 4.5 billion years old as a planetary body, almost as old as the Earth. However, unlike the Earth, the moon lacks the erosive or mountain-building processes that gradually erode craters. Scientists have used the moon’s persistent craters to develop methods for determining the ages of various locations on its surface, in part based on how pocked the area looks to be with craters.

According to this study, the Chang’e-5 moon rocks are just about 2 billion years old. With confidence about the ages of these rocks, scientists can now calibrate their critical chronology tools more precisely, said the researchers.

Other intriguing findings from the study concern the makeup of basalts in the returning samples and their implications for the moon’s volcanic history.

The Science paper’s findings are merely the tip of the iceberg, so to speak. The team now sifting through the regolith samples in search of clues to other significant lunar science questions, such as locating fragments tossed into the Chang’e 5 collection site from distant, young impact craters such as Aristarchus, and possibly determining the ages of these small rocks and the nature of the materials at those other impact sites.

Source: Science, DOI: 10.1126/science.abl7957

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