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When Chinese scientists analyzed soil samples they brought back from the Moon, they noticed something groundbreaking: The soil contained water as well as minerals.
Finding water on the Moon is nothing new in itself. NASA and Indian spacecraft have detected what they believe to be water on the Moon’s surface, and Chinese scientists found water trapped in glass beads scattered across the Moon last year.
But scientists say this latest discovery is the first time that H2O, the molecular form of water, has been found in physical samples and, more importantly, that water has been obtained from a part of the Moon where it was previously thought that water could not exist in this form.
Researchers who closely examined samples collected by China’s Chang’e-5 probe, which landed on the lunar surface in 2020, found a “prismatic, plate-like transparent crystal” about the width of a human hair that is actually an “unknown lunar mineral” called ULM-1, according to the study published July 16 in the journal Nature Astronomy.
According to the study, the ULM-1 crystal (chemical formula (NH4)MgCl3 6H2O) consists of about 41% water and contains ammonia particles that allow the H2O molecules to remain stable despite the large temperature changes on the Moon.
This type of water could be “a potential source for life on the Moon,” the scientists wrote in their study.
The discovery is the latest in China’s broader push to become a dominant space power, with sweeping ambitions including building a research base on the Moon. The work was applauded by enthusiastic Chinese social media users who cite the space programme as a source of national pride.
“The discovery of a hydrous mineral at the Chang’e-5 landing site is fascinating and will further our understanding of rock-vapor reactions in the lunar crust and on the lunar surface,” said David A. Kring, principal scientist at the Lunar and Planetary Institute in Texas, who was not involved in the study.
Hard to remove
There could be three types of water on the Moon, according to planetary geologist Yuqi Qian of the University of Hong Kong, who was not involved in the study.
There are water molecules, the compound we know as H2O; its frozen form, ice; and its close chemical relative, a molecular compound called hydroxyl.
Previous discoveries had suggested that water was present on the Moon when volcanoes erupted in the ancient past, and that lunar water came from these volcanoes, meaning that water came from inside the Moon and has been present since the Moon first existed.
People didn’t always know there was water on the moon, however, and scientists have theorized about its existence for hundreds of years. At times, researchers believed the moon was dry, particularly after they initially failed to find water in samples collected by NASA’s Apollo missions and the Soviet Union’s Luna missions.
It was only in more recent years that scientists discovered that water, ice, and water molecules are mostly found in the dark, cold lunar poles, where the sun doesn’t reach. A recent study also suggested that water, or hydroxyl, may be trapped in glass beads sprinkled across the lunar surface, and that solar winds could convert the hydroxyl (chemical formula OH) into water, or H2O.
But the lunar poles are difficult to navigate because of the rocky terrain, making it a difficult place for humans to extract water. Molecular water is “not stable in other parts of the Moon” and evaporates at lower latitudes, where temperatures can exceed 100 degrees Celsius (212 degrees Fahrenheit), Qian said.
This new study changes that.
The samples taken by China’s Chang’e-5 probe came from the mid-latitude part of the moon at 43.1 degrees latitude – an area that Qian said is normally “not stable for molecular water”. The samples contained ammonium, which acts as a stabilizer for water molecules.
This mechanism also confirms NASA’s findings that traces of water were detected on the lunar surface with the SOFIA telescope in 2020. However, scientists at the time were not able to confirm this finding with physical samples or fully explain how the water remained on the hot surface.
“I think this new finding that we can directly extract molecular water from lunar soil has a lot of potential,” Qian said. “I think this is a new mechanism to stabilize molecular water on the lunar surface.”
Kring, of the Lunar and Planetary Institute, said that although the sample was collected from a mid-latitude region, “it’s not clear whether it formed there.” Impact processes could redistribute the rock across the lunar surface.
China’s space ambitions
A growing number of countries, including the United States, are eyeing the strategic and scientific benefits of expanding lunar exploration.
China has made rapid progress in recent years, reflecting leader Xi Jinping’s “eternal dream” of making the country a space power.
In 2013, China became the first country in nearly four decades to perform a robotic lunar landing. Then in 2019, it became the first and only country to land on the far side of the moon. Three years later, China completed its latest orbital space station, Tiangong.
And it plans more, aiming to land astronauts on the Moon by 2030 and establish a research base at the South Pole.
Experts previously told CNN that understanding how water is stored on the Moon is useful because it could point to potential resources that could one day be turned into drinking water or even rocket fuel for future lunar astronauts.
After the latest study, many Weibo users raised the possibility of growing plants or crops on the moon using molecular water found in the soil. However, Qian said it was too early to draw such conclusions. Growing anything on the moon would depend on factors such as how abundant water is — which requires more research to confirm.
But, he added, “this new phenomenon, this new mechanism… will open the door to finding new water in this new form.”
Kring similarly cautioned that the findings so far “do not have significant implications for exploration mission architectures, but they do show that discoveries await those willing and able to explore the Moon.”
China’s rapid advances have caught the attention of NASA, which has not been allowed to work with Chinese counterparts since 2011, when Congress passed the Wolf Amendment, citing espionage concerns.
However, China made samples of Chang’e-5 available to the international community last August.
“We are currently going through the process with our scientists and our lawyers to make sure that the guidelines and protections that the Chinese are pushing for … do not violate the law, the Wolf Amendment,” NASA Administrator Bill Nelson recently told CNN. “As of now, I don’t see any violations.”
But such issues have hindered China’s participation in the International Space Station (ISS), spurring China’s efforts to build Tiangong, a rival to the US, especially as the ISS prepares to retire in 2031.
These limitations on international space cooperation, and China’s own rise, have led some Chinese social media users to feel vindicated by the latest discovery, with online comments and state media reports praising the progress of the national space program.
“This is a demonstration of our country’s scientific and technological power!” a user wrote on Weibo, a social media site in China, and the hashtag about the invention was viewed 35 million times.
Another user thanked the country’s space program, saying, “We are a global leader in lunar scientific research.”
On Weibo, it was called for more cooperation for the benefit of humanity and stated that the study was published in an international journal reviewed by experts from various countries.
“We can’t work behind closed doors; it would be best to pull all scientists to China,” one wrote.
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