The landing “marked a new chapter in the human race’s lunar and space exploration,” the CNSA said in a statement.
“The far side of the moon is a rare quiet place that is free from interference of radio signals from Earth,” mission spokesman Yu Guobin said. “This probe can fill the gap of low-frequency observation in radio astronomy and will provide important information for studying the origin of stars and nebula evolution.”
Although China, the United States and Russia have operated robotic spacecraft on the moon before, Chang’e 4 is the first to land softly on the side of the satellite that always faces away from Earth. The geology on this side of the moon is distinctive, with more craters and less evidence of volcanic activity. But it is difficult to explore, because scientists on Earth cannot communicate via direct radio signal with spacecraft in this remote region — a quandary China’s relay satellite has solved. The mission transmitted an orange-tinted, high-definition photo of the moon’s lightly pockmarked surface on Thursday
The landing demonstrated China’s ambitions to become a space power and scientific force in an era when NASA funding has generally been shrinking as a percentage of the U.S. federal budget. China spends more on scientific research than any nation but the United States, and it launched more rockets than any other country in 2018. In December, China announced it was starting global service for BeiDou — a homegrown satellite navigation system designed to compete with the U.S. Global Positioning System (GPS) — ahead of schedule.
“This is more than just a landing,” said Alan Duffy, a lead scientist with the Royal Institution of Australia who focuses on space exploration. “Today’s announcement was a clear statement about the level of maturity that China’s technology has now reached. Beijing’s longer-term goal to match U.S. capabilities could now become reality within two decades and on the moon within perhaps only one decade.”
China is far from the only nation with its eye on the lunar surface. India, Israel and Germany also have lander missions planned for this year, and the Russian and Japanese space agencies aim to send spacecraft to the moon in the early 2020s.
“The whole world is raising their game,” said Maria Zuber, a lunar geophysicist at the Massachusetts Institute of Technology.
NASA is not currently developing any robotic spacecraft to operate on the moon’s surface. A sample return mission that would explore the same spot as Chang’e 4 has been proposed but never selected for development by the space agency. The agency’s first rover since the Apollo era, the Resource Prospector mission, was abruptly canceled last spring, stunning many scientists.
However, in November NASA announced it would begin contracting with private aerospace companies to send scientific payloads to the lunar surface. Those missions could start as early as this year.
Chang’e 4 is the latest in a series aimed at exploring the moon and paving the way for Chinese astronauts to eventually land on the lunar surface. Its predecessor, Chang’e 3, delivered a rover called Jade Rabbit to the lunar nearside, where it worked for more than two years. In Chinese mythology, Chang’e is the name of a goddess who lived on the moon.
The Chang’e 4 mission, which is mainly scientific, will use its cameras and ground-penetrating radar to understand the composition of Von Karman crater within the Aitken basin, which Zuber called “a very special location.”
There, it is thought that an ancient meteor impact during the early days of the solar system exposed material from the moon’s deep interior. Obtaining a precise date for the event, and probing the primitive rock it revealed, could help solve lingering mysteries about the formation of the moon and the history of the solar system.
Exploring the Aitken basin has been a top priority for the U.S. National Academies of Sciences, Engineering and Medicine for the past two decades, noted Clive Neal, a Notre Dame geologist who is emeritus chair of the U.S. Lunar Exploration Analysis Group.
“Unfortunately,” he said, that goal “has yet to be realized by a U.S.-led mission.”
Still, Zuber noted the Chang’e 4 instrument suite does not include some of the tools required to probe the full array of questions scientists have about the basin.
“Certainly there will be some great new science,” Zuber said. “But I would say the landing of Chang’e 4 is a teaser for what comes next.”
A spectrometer on board the rover will also conduct low frequency radio astronomy observations away from the noise of Earth’s radio networks. Contrary to popular belief (and Pink Floyd), this side of the moon is not “dark.” But the interaction of Earth’s gravity with the moon’s rotation means it perpetually faces away from us, making it an ideal site to probe the cosmos without interference.
And the static part of the Chang’e 4 lander carries a small, sealed capsule containing plant seeds and insect eggs. If the delicate cargo can be encouraged to germinate and hatch in the moon’s low gravity, they may form a complete biosphere — a tiny oasis of life on a cold and airless world.
China’s space program, whose funding totaled $11 billion in 2017 — compared with $19 billion requested by NASA — has been a source of pride for both the Communist Party and the country’s citizens. In 2003, China became the third country to put an astronaut in space. The country plans to launch a sample return mission to the moon later this year and has ambitions to crew a lunar base, launch a low-orbit space station and send a probe to Mars by the 2020s.
China revealed little about the Chang’e 4 mission in the run-up to the landing; it did not announce beforehand when it would attempt to land the spacecraft. The only information about the landing site and deployment of instruments has come from official Chinese sources.
NASA Administrator Jim Bridenstine congratulated China in a tweet Wednesday night, writing, “This is a first for humanity and an impressive accomplishment.”
Although other countries, including Sweden, contributed instruments to the mission, the United States was not involved. A clause in the appropriations bills for NASA and the White House Office of Science and Technology Policy bars the agencies from collaborating with any Chinese entity.
Proponents of the ban, including its author, former representative Frank Wolf (R-Va.), say it protects U.S. national security. In a report last August, the Pentagon asserted China’s space program was “central to modern warfare.”
But John Logsdon, a professor emeritus at George Washington University Space Policy Institute, called the rule “nonsense.”
“China deserves a seat at the central table in space exploration,” he said. “The success so far of this mission is clear evidence of that reality.”
Planetary scientist Heidi Hammel, who is the executive vice president of the Association of Universities for Research in Astronomy, expressed hope the ban would not stifle international discussions about the mission’s scientific results.
“I’m keenly interested in what they’ve learned . . . especially since [U.S. scientists] have talked about doing the same thing,” she said. “Cooperation is preferable to this wall of silence.”
In China, the official reaction was ebullient. The Global Times, a newspaper run by the Communist Party, took a swipe at the “mania” of world powers that historically participated in the space race — the United States and the Soviet Union — and said China would instead share the data and pictures it obtained and work with any countries committed to the peaceful development of space.
It channeled both President John F. Kennedy and Neil Armstrong in a triumphant editorial.
“We choose to go to the back of the moon not because of the unique glory it brings," it said, "but because this difficult step of destiny is also a forward step for human civilization!”