The moon "grew" 800 million years old
Lunar Soil Research on Chang'e 5 Reveals "Old Life" on the Moon
The moon is very busy.
As the earth’s only natural satellite, it has to be invited to attend a banquet hosted by the Chinese poet Li Bai in the Tang Dynasty during the billions of years of orbiting the earth, and to provide an event venue for the US-Soviet "space race" that started in the middle of the 20th century. We also need to use our own evolutionary process to help people on earth answer "Where do I come from and where do I want to go".
However, how long the moon has "lived", few people can say clearly.
About 4.5 billion years ago, the moon was still a "baby". It was born with a mass of hot magma, showing its vitality to the universe.
After billions of years, the moon gradually entered its "old age", and magma activity gradually ceased until it was completely cooled and "dead"... The old magma turned into an ice-cold moon sea, solidifying the story of time in basalt.
Previously, lunar meteorites on Earth, as well as lunar samples collected by the United States and the Soviet Union, have been telling people that one of the life characteristics of the moon-magma activity lasted about 2.8 billion to 3 billion years ago.
However, there has been controversy in the scientific community about the exact time when the lunar magma activity ceased.
Scientists only pieced together the middle part of the story of the moon's evolution, but know very little about the most critical "beginning" and "end".
How did the "childhood" and "old age" of the moon spend?
Recently, Chinese scientists have finally solved part of the mystery of "old life" on the moon through lunar samples collected by Chang'e-5.
On October 19, the Institute of Geology and Geophysics of the Chinese Academy of Sciences (hereinafter referred to as the "Institute of Geology and Earth") and the National Astronomical Observatory of the Chinese Academy of Sciences jointly published academic papers on related research in the international academic journal Nature.
This study shows that people were wrong before. The magma activity on the moon continued until about 2 billion years ago, and the moon’s lifespan was about 800 million years longer than previously speculated. What’s more interesting is that the latest study also found that, Radioactive elements and water may not be helpful in extending the life of the moon.
What exactly is going on?
The "chess formation" laid out before flying to the moon
To solve scientific problems, we must first have research objects, and one of the best objects for studying the moon is the "lunar soil."
At the Chinese Academy of Sciences’ scientific research results conference held not long ago, Ouyang Ziyuan, an academician of the Chinese Academy of Sciences and Chang’e engineering consultant, said when talking about the importance of “moon soil”: Grab a handful of dirt and come back."
China's lunar exploration project, the Chang'e Project, launched in 2004 has a three-step strategy of "circumnavigation", "falling" and "returning".
Chang'e No. 1 and No. 2 achieved the "circumnavigation" of the moon; Chang'e No. 3 achieved the "landing" of the moon, and Chang'e No. 4 achieved a soft landing on the back of the moon; in 2020, it landed in Chang'e near Lumke Mountain, northwest of the Lunar Storm Ocean On the 5th, we successfully completed our country’s first mission to sample and return extraterrestrial objects, and took back the highly anticipated “lunar native products”.
Collecting "moon soil" here is very particular.
Ouyang Ziyuan stated that choosing to "grab soil" in the ocean of storms is "hoping to add some of the breakthroughs and contributions of our Chinese scientists to the moon's history of 3 billion years ago."
They believe that this place contains the latest basalt formed on the moon, and the story of the moon's "life in old age" is hidden in it.
It can be said that this was a "chess formation" that had been laid before Chang'e 5 went to the moon.
On this side, Chang'e 5 accurately "grabs soil" on the moon, and on the other side, in the Earth Human Laboratory, which is 380,000 kilometers away, it is developing key technologies that can match the lunar research topics in a targeted manner.
Scientists are eager to solve the mystery of the moon one day.
Li Xianhua, the corresponding author of the "Nature" paper, an academician of the Chinese Academy of Sciences, and a researcher at the Institute of Geology and Earth Sciences, told reporters that since 1999, the Chinese Academy of Sciences has begun to build a micro-area in-situ analysis and test platform for earth and planetary science.
With the technical reserves in place, they began to "hope for the stars and the moon."
The moon "lives" longer than imagined
On December 17, 2020, the Chang'e-5 returner loaded with stories about the moon finally landed safely in Siziwang Banner, Inner Mongolia, China.
Many people know what happened after that.
It was confirmed that Chang'e 5 brought back a total of 1,731 grams of lunar samples. This is the first lunar sample that mankind has ushered in again after 44 years.
Many scientists hope to "see the moon's past" from these samples, which are more precious than gold.
More than half a year later, the scientific research team led by the Institute of Geology and Earth Sciences of the Chinese Academy of Sciences and the National Astronomical Observatory obtained a part of the first batch of Chang'e-5 lunar scientific research samples-3 grams of lunar soil powder and two light fragments of rock fragments.
A glass vial containing black moon soil powder was delivered to the hands of young researcher Yang Wei and his colleagues.
To determine the life of the moon, they must first find the basalt particles in the lunar samples that record the "life in old age" on the moon.
But the lunar soil powder is too fine. If it is not handled properly, it will be wiped out by the electrostatic effect on the earth as soon as the bottle cap is opened.
Facing these samples in grams, scientific researchers walked on thin ice.
Yang Wei and several young colleagues wrapped themselves tightly in isolation gowns and entered the ultra-clean laboratory to transfer and sort lunar soil samples. "The leaders are standing outside the door and waiting. Everyone is nervous and looking forward to it. , We will report the progress in one step." Yang Wei said.
Soon, Yang Wei and his colleagues separated basalt particles that were only a few microns in size.
Everyone is very excited: these are "time capsules" that record the history of the moon!
At this point, the research has just begun.
In order for basalt to "tell the story", it is necessary to have a "key" that can pry the mouth of the basalt.
This "key" is the key weapon of Li Xianhua's team-"Ion Probe Ultra-high Spatial Resolution Dating Technology".
Li Xianhua explained that the scientific research team has improved the key hardware of commercial ion probe analysis instruments, which can accurately analyze particles as small as 3 microns.
With such technical reserves, researchers can inspect key parts of basalt in the "ultra-mini" size.
The results of the study show that the formation age of the basalt brought back by Chang'e-5 is 20.30±0.04 billion years, which means that the “youngest” basalt on the moon was formed 2 billion years ago.
Furthermore, there was still magma activity on the moon until 2 billion years ago, which is 800 million years longer than the "life" estimated by scientists before.
This conclusion is equivalent to anchoring a new and critical time point on the "growth curve" of the moon, filling the gap in human understanding of the evolutionary history of the moon's "old age".
800 million more years, then?
Scientists did not stop there. They asked new questions about the evolution of the moon: How did the extra 800 million years come from? In other words, why did the moon remain alive 2 billion years ago?
Two hypotheses were overturned one after another
The cause of the most late magma activity on the moon has always been an unsolved mystery.
Previously, there were two explanations in the scientific community: one possibility is that the source area of magma is rich in radioactive elements, which provides a heat source for magma production; the other possibility is that the source area of magma is rich in water, thus reducing the rock’s Melting point.
In order to verify the hypothesis that the source area is rich in radioactive elements, another weapon that has been studied by the Institute of Geology and Earth of the Chinese Academy of Sciences for many years-"ultra-high spatial resolution isotope analysis technology" debuted.
The results of the study were unexpected: the researchers did not find radioactive heat-generating elements such as potassium, rare earth elements, and phosphorus's "Krip material" during the initial melting of the basalt sample.
In other words, scientists had previously misunderstood the moon, and the first hypothesis was overturned.
In order to verify the hypothesis that the magma region is rich in water, the third weapon of the scientific research team-"nano-ion probe analysis technology" came in handy.
By measuring the water content and hydrogen isotopic composition of the Chang'e-5 basalt, the researchers found that "if the source rock is divided into 1 million parts by weight, the water content only accounts for 1-5 parts", which indicates that the moon mantle is very "dry" , Is not rich in water.
In other words, scientists once again misunderstood the moon, and the second hypothesis was also overturned.
It is neither a radioactive element nor water. So what is it that leads to the extension of the moon’s lifespan?
More lunar stories to be revealed
Li Xianhua doesn't know the answer yet.
He told reporters that this series of latest studies has raised new scientific questions for the study of the lunar thermal evolution history. "The reason why the moon is cooling so slowly is not clear. A new theoretical framework and evolutionary model is needed for future lunar exploration and research. Research suggests a new direction."
What is gratifying is that the research team exploring the mysteries of the moon is continuing to grow.
Xu Yigang, a member of the National Space Administration's Chang'e-5 Lunar Samples Expert Committee and academician of the Chinese Academy of Sciences, said on the day of the Chinese Academy of Sciences' results announcement that another batch of lunar research samples have been distributed to scientists in the near future.
Researchers interested in this can apply to the committee for samples.
The future is connected to the past, and scientists are like catalysts of time, always bringing surprises.
"The heavens and the earth are yellow, the universe is wild. The sun and the moon are shining, and the sun and the stars are standing. The cold and the summer, the autumn and winter are hidden." The life course of the moon predicts the evolution of the earth to some extent, and more stories need to be revealed.
"The moon's life extension is not because of radioactive elements and water, but what is it? Our research is still going on." Yang Wei told reporters with a smile.
China Youth Daily and China Youth Daily reporter Zhang Qian Source: China Youth Daily
Version 12, October 26, 2021