Chinese researchers from the Harbin Institute of Technology and the Chinese Academy of Sciences have issued a critical warning ahead of a world-first lunar mission: simply touching water ice on the moon could cause it to vanish into the vacuum of space. Their findings, crucial to the upcoming Chang’e-7 mission, reveal that the very act of sampling could undermine scientific results by “an order of magnitude” if not carefully corrected for.
This year, China’s Chang’e-7 spacecraft is set to become the first mission to attempt direct sampling and measurement of lunar water ice, targeting a landing near the rim of Shackleton crater at the moon’s south pole. The discovery of accessible water is the holy grail of lunar exploration, key to future human outposts for drinking water, oxygen, and rocket fuel. However, a new paper accepted by the Chinese Journal of Space Science highlights a formidable paradox. Lunar water doesn’t exist in puddles or ice cubes; it’s trapped within frozen soil, held in place only by extreme cold and the moon’s near-perfect vacuum. The moment a sampling tool disturbs that frozen regolith, even slight friction-induced warmth can cause the ice to sublimate—turning directly from solid to vapour and escaping instantly into space.
“The rover’s robotic arm scrapes into icy soil, even slight warming from contact and friction could loosen water molecules,” the research team wrote, according to their paper. Without an atmosphere to contain it, this vapour is lost forever. If these unintended losses aren’t accounted for, the Chang’e-7 mission’s measurements could be thrown off dramatically, “severely undermining the reliability of the resulting scientific conclusions,” the scientists cautioned.
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To solve this, the team has developed an intricate sampling and calibration system. The rover’s sampler won’t scoop or drill aggressively. Instead, it uses a thin plate on a robotic arm to gently press and rotate into the ground, collecting a minuscule sample—about the weight of a pinch of salt. This plate is then sealed and transferred into an analysis chamber inside the rover, where the sample is gently heated to release vapour in a controlled environment. “There, it is gently heated so scientists can measure how much water vapour is released and estimate the soil’s water content, a stage where losses are far more controllable,” the team stated.
The mission will carry at least 30 of these sampling plates, allowing for multiple tests from different locations and depths. To prepare, the scientists conducted experiments using artificial lunar soil, created based on Apollo 16 samples, under cryogenic, near-vacuum conditions mimicking the lunar south pole. These tests confirmed the sampler’s technical feasibility but also quantified the pervasive challenge of water loss at every stage. Their solution is a sophisticated calibration method that uses sensor data from the sampling process itself to mathematically reconstruct how much water was lost from the moment of first contact.
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“On the one hand, we verified that the micro-sampling device used by the lunar volatile measurement instrument is technically feasible,” the researchers concluded. “On the other hand, this work provides a foundation for processing and interpreting data during future operations on the moon.” This meticulous groundwork is essential because, while orbital remote sensing has mapped where ice likely exists, only in-situ measurement can reveal its true form, concentration, and extractability.
Scheduled for launch later this year from the Wenchang space launch centre, Chang’e-7 represents a monumental step in China’s lunar exploration roadmap, which aims for a research base near the south pole by around 2035. The mission carries over 15 scientific instruments and is designed to operate for an unprecedented eight years. By confronting the delicate physics of lunar ice head-on, Chinese scientists are not just planning to touch the moon’s water; they’re learning how to hold onto it long enough to understand its true potential.
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