Published : 05/06/2026
The primary focus and main attraction of China's Chang'e-7 (嫦娥七號) lunar mission is the search for water at the moon's south pole.
But why are scientists so relentless in their quest for water on the moon? And if water is indeed to be found there, why target the south pole in particular?
Chang'e-7｜Scientists once believed the Moon was a waterless world
Let's start with the question of whether there is water on the Moon at all. The scientific consensus on this issue once saw a "major reversal".
For a long time, it was almost universally accepted in the scientific community that the moon was entirely bone-dry. This was partly due to the "Giant Impact" hypothesis of lunar origin, which suggested that the immense heat generated by the collision would have completely evaporated any water.
Furthermore, between 1969 and 1972, the American Apollo missions brought back soil samples that showed no evidence of water, while the instruments left behind on the lunar surface failed to detect any water vapour.
This consensus began to change in the 1990s. As new detection technologies emerged, scientists discovered that the lunar north and south poles, areas untouched by humans or probes, particularly the South Pole, contained large amounts of hydrogen.
Hydrogen is one of the chemical components of water, from which the presence of water was inferred, possibly in the form of water ice. By 2009, data from India's "Chandrayaan-1" probe in lunar orbit further supported this view.
As for where the water on the Moon came from, current theories include that it was left behind by impacts from water-carrying asteroids, or formed by collisions with ionised molecules from the solar wind, among others.
Read more: China may become the first to find water on the Moon ?｜Chang'e-7 Ⅰ
Chang'e-7｜"Cold traps" could preserve water ice for billions of years
As for why the lunar south pole is the most likely place to find water, the answer lies in the tilt of the moon's rotational axis.
Because this tilt is incredibly small, the sun merely hovers near the horizon at the lunar poles, keeping the angle of sunlight very low.
Consequently, the terrain at the south pole creates obstructions, casting permanent shadows that sunlight can never reach. This region is also pocketed with numerous impact craters, whose interiors remain in perpetual darkness and are unimaginably cold.
The temperature at the lunar south pole is between minus 173 and minus 113 degrees Celsius, while inside the craters it can be as low as minus 233 degrees Celsius; these are also known as "cold traps".
Scientists believe that water ice can remain stably preserved here for billions of years, which is why "cold traps" are the most likely places to find water on the Moon.
Of course, finding solid evidence is more important than any theory or speculation. Finding water at the lunar south pole is an important goal for the aerospace and scientific communities at this stage.
Why are scientists trying everything they can to find water on the moon?
One reason is for scientific research. Scientists want to understand both where the Moon came from and hope to obtain more information about the origin and evolution of the solar system from the Moon's water.
Chang'e-7｜Lunar water sources can help humanity explore distant planets
Secondly, it is an essential need for human space exploration.
Water can be drunk, and can also be used to produce oxygen through electrolysis. Both are essential for human survival.
If the Moon has water and can produce oxygen, future astronauts could hopefully stay on the Moon for long periods without being highly dependent on supplies from Earth, and furthermore, use the moon as a supply base and a "springboard" to explore Mars or more distant planets.
Therefore, if Chang'e-7 can find water, it will be an important milestone in human exploration of the universe.
According to the plan, China's lunar exploration programme plans to achieve a manned Moon landing around 2030, and will subsequently establish a lunar base, making the search for water sources urgent.
One point must be added: China's Chang'e-5, launched in 2020, brought back 1,731 grams of soil from the Moon, which were the first new lunar samples obtained by humanity in 44 years.
Subsequently, Chinese scientists discovered water molecules in the samples for the first time and confirmed that by heating to 1,000 degrees and through chemical reactions, 51 to 76 litres of water can be produced from each tonne of lunar soil.
However, "man-made water" technologies are complex and relatively inefficient, involving issues such as high energy consumption and extreme temperatures. Because of these significant limitations, directly locating a water source on the moon remains the optimal choice at this stage.
(The cover image is generated by AI)