Chang'e-5 samples reveal key age of moon rocks
Scientists share analysis of first fresh samples from the moon in more
than 40 years

Date:
October 7, 2021
Source:
Washington University in St. Louis
Summary:
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. Now an international team of scientists has
determined the age of these moon rocks at close to 1.97 billion
years old.



FULL STORY ========================================================================== [Moon (stock | Credit: (c) Simon van Hemert / stock.adobe.com] Moon
(stock image).

Credit: (c) Simon van Hemert / stock.adobe.com [Moon (stock | Credit:
(c) Simon van Hemert / stock.adobe.com] Moon (stock image).

Credit: (c) Simon van Hemert / stock.adobe.com Close 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. Now an international team of scientists -- including an expert from Washington University in St. Louis -- has determined the age of these moon rocks
at close to 1.97 billion years old.


==========================================================================
"It is the perfect sample to close a 2-billion-year gap," said Brad
Jolliff, the Scott Rudolph Professor of Earth and Planetary Sciences in
Arts & Sciences and director of the university's McDonnell Center for
the Space Sciences.

Jolliff is a U.S.-based co-author of an analysis of the new moon rocks
led by the Chinese Academy of Geological Sciences, published Oct. 7 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
to Earth rocks from some of the youngest volcanic surfaces on the moon.

"Of course, 'young' is relative," Jolliff said. "All of the volcanic
rocks collected by Apollo were older than 3 billion years. And all of the
young impact craters whose ages have been determined from the analysis
of samples are younger than 1 billion years. So the Chang'e-5 samples
fill a critical gap." The gap that Jolliff references is important not
only for studying the moon, but also for studying other rocky planets
in the solar system.

As a planetary body, the moon itself is about 4.5 billion years old,
almost as old as the Earth. But unlike the Earth, the moon doesn't have
the erosive or mountain-building processes that tend to erase craters
over the years.

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.



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

"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," Jolliff said. "But to put absolute age dates on that,
one has to have samples from 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 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." "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." 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.



==========================================================================
The results presented in the Science paper are just the tip of the
iceberg, so to speak. 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.

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. 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.

"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.

"The consortium includes members from China, Australia, the U.S.,
the U.K. and Sweden," Jolliff continued. "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. This is
diplomacy by science." Jolliff is a specialist in mineralogy and provided
his expertise for this study of the Chang'e-5 samples. His personal
research background is focused on the moon and Mars, the materials that
make up their surfaces and what they tell about the planets' history.

As a member of the Lunar Reconnaissance Orbiter Camera science team and
leader of the Washington University team in support of NASA's Apollo
Next Generation Sample Analysis (ANGSA) program, Jolliff investigates
the surface of the moon, relating what can be seen from orbit to what
is known about the moon through the study of lunar meteorites and Apollo samples -- and now, from Chang'e- 5 samples.

========================================================================== Story Source: Materials provided by
Washington_University_in_St._Louis. Original written by Talia
Ogliore. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
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Location_where_Chang'e-5_landed_on_the_moon_on_Dec._1,_2020_identified.

========================================================================== Journal Reference:
1. Xiaochao Che Alexander Nemchin Dunyi Liu Tao Long Chen Wang Marc D.

Norman Katherine H. Joy Romain Tartese James Head Bradley Jolliff
Joshua F. Snape Clive R. Neal Martin J. Whitehouse Carolyn Crow
Gretchen Benedix Fred Jourdan Zhiqing Yang Chun Yang Jianhui Liu
Shiwen Xie Zemin Bao Runlong Fan Dapeng Li Zengsheng Li Stuart
G. Webb. Age and composition of young basalts on the Moon, measured
from samples returned by Chang'e-5.

Science, 07 Oct 2021 DOI: 10.1126/science.abl7957 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211007145754.htm

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