Chinese Chang’e-5 samples reveal key age of moon rocks – first fresh moon samples in over 40 years

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Illustration of a Chinese Chang’e 5 spacecraft artist returning samples. Credit: CNSA / NASA

Scientists share analysis of the first fresh samples from the moon in more than 40 years.

A lunar probe launched by the Chinese space agency recently brought back the first fresh samples of rock and debris from the moon in more than 40 years. Today, an international team of scientists – including an expert from Washington University in St. Louis – has determined the age of these moon rocks at nearly 1.97 billion years.

“This is the perfect sample to fill a 2 billion year gap,” said Brad Jolliff, Scott Rudolph professor of earth and planetary sciences in arts and sciences and director of the McDonnell Center for the Space Sciences. university. Jolliff is a United States-based co-author of a New Moon Rock Analysis led by the Chinese Academy of Geological Sciences, published on October 7, 2021 in the journal Science.

The age determination is among the first scientific results reported from the successful Chang’e-5 mission, which was designed to collect and return rocks to Earth from some of the moon’s youngest volcanic surfaces.

Chang'e 5 spaceship location

A symbol marks the spot (top left) where the Chang’e-5 spacecraft landed and collected samples on the moon. (Image created with: Lunar QuickMap [https://quickmap.lroc.asu.edu], a collaboration between NASA, Arizona State University and Applied Coherent Technology Corp.)

“Of course ‘young’ is relative,” Jolliff said. “All the volcanic rocks collected by Apollo were over 3 billion years old. And all of the young impact craters whose age has been determined from analysis of samples are less than a billion years old. The Chang’e-5 samples therefore fill a critical gap.

The gap Jolliff refers to is important not only for the study of the moon, but also for the study of other rocky planets in the solar system.

As a planetary body, the moon itself is around 4.5 billion years old, almost as old as the Earth. But unlike the Earth, the Moon does not have the erosion or mountain-forming processes that tend to clear craters over the years. Scientists have taken advantage of the moon’s persistent craters to develop methods of estimating the age of different regions of its surface, based in part on how the area appears to be cratered.

This study shows that the lunar rocks returned by Chang’e-5 are only about 2 billion years old. Knowing with certainty the age of these rocks, scientists are now able to more precisely calibrate their important timeline tools, Jolliff said.

“It’s a phenomenal result. In terms of planetary time, this is a very precise determination.
Brad jolliff

“Planetary scientists know that the more craters there are on a surface, the older it is; the fewer craters, the younger the surface. It’s a nice relative determination, ”said Jolliff. “But to put absolute age dates on that, you have to have samples of those surfaces.”

“The Apollo samples gave us a number of surfaces that we were able to date and correlate with crater densities,” Jolliff explained. “This chronology of craters has been extended to other planets – for example, for Mercury and ">March – to say that surfaces with a certain density of craters have a certain age.

“In this study, we got a very specific age around 2 billion years, plus or minus 50 million years,” Jolliff said. “It’s a phenomenal result. In terms of planetary time, this is a very precise determination. And that is enough to distinguish the different formulations of the timeline.

Other interesting findings from the study concern the composition of basalts in the returned samples and what this means for the volcanic history of the moon, Jolliff noted.

The results presented in the Science article are just the tip of the iceberg, so to speak. Jolliff and his colleagues are now examining the regolith samples for keys to other important lunar science problems, such as finding pieces and pieces thrown into the Chang’e-5 collection site from craters in ‘impact distant and young such as Aristarchus, to eventually determine ages. of these small rocks and the nature of the materials of these other impact sites.

Jolliff worked for more than 15 years with scientists from the High-Resolution Sensitive Ion Microprobe Center (SHRIMP) in Beijing who led this study, including study co-author Dunyi Liu. This long-term relationship is made possible by a special collaborative arrangement that includes the University of Washington and its Department of Earth and Planetary Sciences, and Shandong University in Weihai, China, with the support of McDonnell Center for the Space Sciences at the University of Washington.

“The Beijing lab where the new analyzes were done is among the best in the world, and they did a phenomenal job characterizing and analyzing the volcanic rock samples,” Jolliff said.

“The consortium includes members from China, Australia, US, UK and Sweden,” Jolliff continued. “This is science done in the ideal way: international collaboration, with free sharing of data and knowledge – and all done in the most collegial way possible. It is diplomacy through science.

Jolliff is a specialist in mineralogy and brought his expertise to this study of the Chang’e-5 samples. His personal research focuses on the Moon and Mars, the materials that make up their surfaces and what they tell about the history of the planets.

As a member of the Lunar Reconnaissance Orbiter Camera science team and team leader at the University of Washington in support of ">NasaApollo’s Next Generation Sample Analysis Program (ANGSA), Jolliff studies the surface of the moon, connecting what can be seen from orbit to what is known about the moon through the study lunar meteorites and samples from Apollo – and now, Chang ‘e-5 samples.

Reference: “Age and composition of young basalts on the Moon, measured from samples returned by Chang’e-5” October 7, 2021, Science.
DOI: 10.1126 / science.abl7957


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