Water signals were observed in reflectance spectral data from the lunar surface acquired by the Chang'e-5 lander, a joint research team led by Lin Yangting and Lin Honglei from the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGGCAS) has announced, providing the first evidence of in-situ detection of water on the Moon.
The lunar soil at the landing site contains fewer than 120 parts-per-million (ppm), or 120 grams water per tons, according to a study published on Saturday in the peer-reviewed journal Science Advances, and a light vesicular rock comprises 180 ppm - significantly drier than rocks on Earth.
Remote observation had proven the presence of water, but the lander has now discovered evidence of water in rocks and soil.
The Chang'e-5 spacecraft returned 1,731 g of samples after landing on one of the Moon's youngest mare basalts in a mid-high latitude. However, before sampling and delivering the lunar soil to Earth, the lander's lunar mineralogical spectrometer (LMS) measured the spectral reflectance of the regolith and a rock, offering a unique opportunity to identify lunar surface water.
Scientists believe the soil acquired water via solar wind, but the rock's higher water content came from an unknown source beneath the Moon's surface - the rock could have been expelled from deeper within the moon during a previous volcanic eruption.
The scientists also stated that simulating true lunar surface conditions on Earth is difficult, emphasizing the need for in-situ measurements.
The findings are consistent with a preliminary analysis of the returning Chang'e 5 samples, the report indicated.
Previous evidence supporting the presence of water on the Moon has been discovered, but all of them have been based on lunar samples returned to Earth or data obtained by instruments from afar.
Water molecules were discovered trapped inside glassy, volcanic stones during Apollo missions in the 1960s and 1970s, based on an analysis of lunar rock samples collected during the Apollo missions in 2008.
In 2018, scientists used data from NASA's Moon Mineralogy Mapper aboard India's Chandrayaan-1 lunar probe to demonstrate the presence of water ice on the Moon's surface.
NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) flew a modified Boeing 747 outfitted with a powerful telescope in 2020, confirming for the first time that water exists on the Moon's sunlit surface.
This newest confirmation of water on the Moon's surface by the Chang'e 5 lander was made on-site rather than from lunar orbit or Earth, marking a historic first.
The discoveries add to the mystery surrounding China's Chang'e-6 and Chang'e-7 missions. According to the report, investigations into lunar water reserves are becoming more prominent as the construction of crewed lunar stations is planned over the next few decades.
