Jolliff is a specialist in mineralogy and provided his expertise for this study of the Chang’e-5 samples. “This is science done in the ideal way: an international collaboration, with free sharing of data and knowledge - and all done in the most collegial way possible. “The consortium includes members from China, Australia, the U.S., the U.K. “The lab in Beijing where the new analyses were done is among the best in the world, and they did a phenomenal job in characterizing and analyzing the volcanic rock samples,” Jolliff said. This long-term relationship is possible through a special collaboration agreement that includes Washington University and its Department of Earth and Planetary Sciences, and Shandong University in Weihai, China, with support from Washington University’s McDonnell Center for the Space Sciences. Jolliff has worked with the scientists at the Sensitive High Resolution Ion MicroProbe (SHRIMP) Center in Beijing that led this study, including study co-author Dunyi Liu, for over 15 years. Jolliff and colleagues are now sifting through the regolith samples for keys to other significant lunar science issues, such as finding bits and pieces tossed into the Chang’e-5 collection site from distant, young impact craters such as Aristarchus, to possibly determining the ages of these small rocks and the nature of the materials at those other impact sites. The results presented in the Science paper are just the tip of the iceberg, so to speak. Other interesting findings from the study relate to the composition of basalts in the returned samples and what that means for the moon’s volcanic history, Jolliff noted. And that’s good enough to distinguish between the different formulations of the chronology.” In terms of planetary time, that’s a very precise determination. “In this study, we got a very precise age right around 2 billion years, plus or minus 50 million years,” Jolliff said. “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 Apollo samples gave us a number of surfaces that we were able to date and correlate with crater densities,” Jolliff explained. “But to put absolute age dates on that, one has to have samples from those surfaces.” That’s a nice relative determination,” Jolliff said. “Planetary scientists know that the more craters on a surface, the older it is the fewer craters, the younger the surface. In terms of planetary time, that’s a very precise determination.” Knowing the age of these rocks with certainty, scientists are now able to more accurately calibrate their important chronology tools, Jolliff said. This study shows that the moon rocks returned by Chang’e-5 are only about 2 billion years old. Scientists have taken advantage of the moon’s enduring craters to develop methods of estimating the ages of different regions on its surface, based in part on how pocked by craters the area appears to be. But unlike the Earth, the moon doesn’t have the erosive or mountain-building processes that tend to erase craters over the years. The gap that Jolliff references is important not only for studying the moon, but also for studying other rocky planets in the solar system.Īs a planetary body, the moon itself is about 4.5 billion years old, almost as old as the Earth. So the Chang’e-5 samples fill a critical gap.” And all of the young impact craters whose ages have been determined from the analysis of samples are younger than 1 billion years. “All of the volcanic rocks collected by Apollo were older than 3 billion years. (Image created with: Lunar QuickMap, a collaboration between NASA, Arizona State University & Applied Coherent Technology Corp.) “Of course, ‘young’ is relative,” Jolliff said. A symbol marks the spot (upper left) where the Chang’e-5 spacecraft landed and collected samples on the moon.
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