Surface of the Moon with Earth in the background

China’s lander finds water on the Moon

Image credit: Dreamstime

China's Chang'e-5 lunar lander has become the first to detect native water on the Moon in real time.

Chang'e-5, the lunar lander designed by China, has found water at its landing site using spectral reflectance measurements of soil and rocks.

The lunar unit landed near Oceanus Procellarum on the Moon's near side in 2020, where it collected and tested over 60oz (approximately 1.7kg) of lunar samples from a core about three feet deep. The findings were validated through the analysis of samples the lander returned to Earth in 2021. Now, the Chang'e-5 team has published the conclusions of the experiment in the journal Nature Communications.

Although it was India's Chandrayaan-1 mission that first detected the presence of water on the Moon from orbit, using NASA's Moon Mineralogy Mapper instrument, no mission has been able to confirm these findings on-site.

"For the first time in the world, the results of laboratory analysis of lunar return samples and spectral data from in-situ lunar surface surveys were used jointly to examine the presence, form and amount of 'water' in lunar samples," said co-corresponding author Li Chunlai, from the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC).

"The results accurately answer the question of the distribution characteristics and source of water in the Chang'e-5 landing zone and provide a ground truth for the interpretation and estimation of water signals in remote sensing survey data."

Instead of identifying the presence of rivers or springs on the Moon, the lander was able to confirm the presence of 30 hydroxyl parts per million in lunar rocks and soil - the most common result of water molecules chemically reacting with other matter.

Schematic diagram of Chang’E-5 in-situ laboratory sample analysis.

Chang’E-5 in-situ laboratory sample analysis. / CNSA/GRAS

Image credit: CNSA/GRAS

The samples were collected during the hottest part of the Moon's day, at temperatures nearing 200°F (93°C), when the surface would be at its driest. The timing also coincides with low solar winds, which can contribute to hydration at high enough power.

The scientists’ findings showed that the origins of the hydroxyl were twofold: a small portion appeared in glassy material made by solar winds interfering with the lunar surface, while the bulk of the hydroxyl in the Chang'e-5 samples was contained in apatite, a crystalline, phosphate-rich mineral.

"This excess hydroxyl is indigenous, demonstrating the presence of lunar-originated internal water in the Chang'e-5 lunar samples and that water played an important role in the formation and crystallisation of the late lunar basaltic magma," Li said.

The researchers are planning further lunar explorations with Chang'e-5's successors, Chang'e-6 and Chang'e-7. According to Li, they will continue researching lunar water via remote sensing, on-site detection and laboratory analysis to better understand the source, distribution and temporal variation of lunar water, including polar ice.

China has launched several successful Moon missions in recent years and plans to send Chang'e-6 to collect samples from the far side of the Moon in 2024.

“Lunar water is expected to provide support for future human lunar in-situ resources,” Li said.

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