When China’s Chang’e-5 lunar spacecraft returned to Earth last December, it brought with it the first sample of moon rocks collected in more than 40 years. An international team of researchers has been hard at work analyzing part of this precious sample and has found that it contains some of the youngest volcanic lunar material discovered to date.
The team of researchers found that the sample was around 1.97 billion years old. Although the moon today is volcanically inactive, over its 4.5-billion-year history it has had significant volcanic activity which has shaped its development, like lava which flowed across its surface and formed lava tubes beneath the surface.
Knowing the exact date of the sample is important for accurately dating the moon’s geological history in absolute terms. “Planetary scientists know that the more craters on a surface, the older it is; the fewer craters, the younger the surface. That’s a nice relative determination,” explained one of the researchers, Brad Jolliff of the Washington University in St. Louis, in a statement. “But to put absolute age dates on that, one has to have samples from those surfaces.”
Previous volcanic samples from the moon, like those collected during the Apollo missions, were more than 3 billion years old. And researchers have been able to date impact craters, where the moon was struck by asteroids or comets, to less than 1 billion years old. But there was a gap between these two periods which has now been filled.
“In this study, we got a very precise age right around 2 billion years, plus or minus 50 million years,” Jolliff said. “It’s a phenomenal result. In terms of planetary time, that’s a very precise determination. And that’s good enough to distinguish between the different formulations of the chronology.”
This understanding isn’t only useful for learning about the moon. It can also teach us about rocky planets in our solar system and beyond. “The Apollo samples gave us a number of surfaces that we were able to date and correlate with crater densities,” Jolliff explained. “This cratering chronology has been extended to other planets — for example, for Mercury and Mars — to say that surfaces with a certain density of craters have a certain age.”
The findings are published in the journal Science.
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