Agence France-Presse — Getty Images China plans to, as soon as early Monday morning, launch a spacecraft to the moon’s surface that aims to be the first to bring back lunar rocks in more than four decades. The mission, Chang’e-5, is the latest step in an ambitious space program that China hopes will culminate with an international lunar research station and ultimately a human colony on the moon by the 2030s. If Chang’e-5 is successful, China will be only the third nation to bring pieces of the moon back to Earth. NASA astronauts accomplished that feat during the Apollo moon landings , as did the Soviet Union’s Luna robotic landers, ending with Luna 24 in 1976. Those samples made major contributions to our understanding of the solar system’s evolution, and planetary scientists have waited eagerly for the day more samples would be brought back to Earth. “This is a really audacious mission,” said David S. Draper, the deputy chief scientist at NASA. “They’re going to move the ball down the field in a big way with respect to understanding a lot of things that are important about lunar history.” There has been a revival of interest in returning to the moon in the past couple of decades after the discovery of frozen water in shadowed craters in the polar regions. NASA has set a goal to send astronauts on new moon landings in the coming years with its Artemis program . Commercial companies — some under contract to NASA — are aiming to send robotic landers to the moon in the next year or two. India and an Israeli nonprofit tried to land spacecraft on the moon in 2019, but both spacecraft crashed. In this century, so far only China has successfully put robotic spacecraft on the surface of the moon: Chang’e-3 in December 2013 , and Chang’e-4 , which in January 2019 became the first spacecraft to land on the far side of the moon . Chang’e-4 is still roving and studying lunar geology nearly two years later. Although it started much later than the United States and the Soviet Union, China has made huge progress over the past decade , putting it among the elite ranks of space-faring nations. In addition to the lunar missions, China’s astronauts have docked in orbit with space stations of the country’s own construction three times. In July, the Tianwen-1 mission set course for Mars, and will try to land on the red planet’s surface next year . These accomplishments have become a source of national pride, carefully managed to emphasize the Communist Party’s strong and steady leadership. China’s space program remains secretive, but officials have offered more details than usual about Chang’e-5 — a sign perhaps of growing confidence in the proven track record of the missions. The entire Chang’e-5 mission, from liftoff to the recovery of the rock samples, will be over in less than a month. After the spacecraft enters orbit around the moon, Chang’e-5 will split into two: A lander will head to the surface while the other piece, an orbiter, waits for its return. Once it gets to the surface, the lander needs to accomplish all of its drilling and scooping tasks within a single lunar day, which lasts 14 Earth days. The lander is not designed to survive the frigid dark lunar night. The Chang’e-5 lander includes a small rocket, and before the sun sets it will blast off with the rock and soil samples. This rocket will rendezvous and dock with the piece of the spacecraft that remained in orbit. The samples will be transferred to the orbiter for the journey back to Earth. The sample is scheduled to land in the Inner Mongolia region of China in the middle of December. In an interview with China’s state television network , Yu Dengyun, deputy chief designer of China’s lunar exploration project, acknowledged that the complex choreography of Chang’e-5 was more technically challenging than that of earlier missions. “We launch rockets on the ground with relatively mature technology, but we are using the lander as the launching platform on the lunar surface,” he said. “How to dissipate heat, how to divert flows and how to control the rising process are what we have never done before. These are hard nuts to crack.” Chang’e-5 aims to deliver more than four pounds of specimens back to Earth. In the 1970s, three successful Soviet Luna missions brought back a total of about 10 ounces of moon. NASA’s Apollo astronauts lugged back 842 pounds of moon rock and soil. S cientists are still studying the Apollo and Luna samples. The landing site is a volcanic plain called Mons Rümker in the Oceanus Procellarum region on the moon’s near side. For planetary scientists, rocks collected from this region promise a glimpse of a much younger part of the moon. The places explored by Apollo and Luna were all more than three billion years old. Mons Rümker is estimated to be around 1.2 billion years old. Because it is so different from those earlier sites, “it’s possible to get new science outcomes,” Xiao Long, a planetary geologist at the China University of Geosciences in Wuhan, who was involved in selecting the landing site, said in an email. Planetary scientists hope that rocks brought back by Chang’e-5 can calibrate a crater-counting technique used to estimate the ages of geological surfaces on the planets, moons and asteroids throughout the solar system. A young surface is smooth and almost unblemished, while an old surface is more heavily cratered. But until Apollo, counting craters provided only relative ages; scientists could tell that one place was older than the other but not exactly how old. With moon rocks collected by Neil Armstrong and other astronauts, scientists could measure radioactive elements in the rocks and precisely calculate when a volcanic eruption had occurred, and thus the age of the parts of the moon where the Apollo explorers set down. But none of the missions landed on a younger part of the moon, leaving a large gap of uncertainty. The eastern half of Mons Rümker is a plain of basalt — a rock of hardened lava — that is relatively crater-free, suggesting an age not much more than one billion years. “It has implications way beyond the moon,” said James W. Head III, a professor of geological sciences at Brown University who participated in analyzing Mons Rümker with Dr. Xiao and other Chinese scientists. “So it’s really a great place to go.” Scientists also want to understand some of the differences in composition of varying parts of the moon, and the samples might also explain how part of the moon was still molten some three billion years after it formed. For example, they want to see whether rocks from Möns Rumker contain high levels of thorium. If the moon’s upper mantle in this region contained an abundance of that radioactive element, which generates heat as it decays, that might have produced the volcanism that spilled lava onto the surface before cooling into the basaltic plain. “Or is there some other factor, or is the interior still hot?” Dr. Head asked. “By sampling these, we will be able tell whether these are high thorium or not. And if not, that resets that whole question.” If there is little thorium, “scientists will need to rethink how this young volcanic rock was created,” Dr. Xiao said. To study these and other questions, Carolyn H. van der Bogert, a research scientist at the Institute for Planetology at the Westfälische Wilhelms-Universität in Münster, Germany, said researchers needed more than the wealth of data that has been gathered by orbiting spacecraft such as NASA’s Lunar Reconnaissance Orbiter. “What we really need now are very targeted ground truth missions,” Dr. van der Bogert said. Missions like Chang’e-5, she added, “are going to be really critical for testing and improving our remote sensing data sets.” Claire Fu contributed research.