When scientists from Ahmedabad’s Physical Research Laboratory (PRL) sat down to analyse the crucial data from Chandrayaan-3, they noticed large, yet highly localised variations in the surface temperatures on the Moon. This sparked another intriguing finding from India’s historic mission to the Moon launched in 2023.
According to the team, ice may be present a few centimetres below the Moon’s surface, in more areas of the lunar polar regions than previously thought. The findings are crucial because they help us understand the availability of water on the Moon, better than before. This is also the key to future long-term exploration of the Moon which depends on the availability of ice to provide water.
So far, global scientists have only relied on previous remote sensing data. Direct measurements of the lunar surface temperatures are only available from the Apollo missions of the 1970s. However, these missions landed near the equator, several thousand kilometres from the proposed landing sites for future manned missions, and where terrain slope has little effect on temperature. But ISRO’s mission landed at a high-altitude site near to the South Pole of the moon on August 23, 2023.
WHAT CLUES LED TO THE DISCOVERY?
The team of scientists from PRL Ahmedabad led by Durga Prasad analysed temperature readings taken at the lunar surface by Chandra’s Surface Thermophysical Experiment (ChaSTE) – a thermal probe experiment on Chandrayaan-3’s Vikram Lander, which touched down at the edge of the south polar region. Its arm went to a depth of 10 centimetres below the lunar regolith (soil) collecting data on temperature changes.
Scientists noticed that the temperatures at the landing site, a Sun-facing slope angled at 6℃ peaked at 355 Kelvin – almost 82℃ and dropped to 105 Kelvin (-168℃) during the lunar night. However, a lower peak temperature of 332 Kelvin (59℃) was measured on a flat region approximately a metre from the Lander.
They derived a model using this data to show how the slope angle affects surface temperature at high lunar latitudes. The model indicated that for slopes facing away from the Sun, and towards the nearest pole, a slope with greater than 14℃ angles may be cool enough for ice to accumulate close to the surface. This led scientists to conclude that local topography of the Moon can affect temperatures, especially at high-altitudes, unlike in equatorial regions.
So, the larger slopes facing the pole at high altitudes may contain water ice, making them promising sites for future lunar exploration and habitation, they concluded. This is similar to conditions at the lunar poles, including those at the proposed landing sites for NASA’s manned Artemis missions near the lunar south pole.
CRUCIAL FOR FUTURE LUNAR EXPLORATION
It led the team to suggest that areas on the Moon where ice can form may be more numerous and easier to access than previously thought. The latest findings have been published in Nature’s peer-reviewed journal Communications Earth and Environment.
The discovery follows ISRO’s major breakthrough in 2008, when the first mission to the Moon provided evidence of water on the moon. Last year, the Chandrayaan-3 data also provided evidence of an ocean of magma which once existed on the Moon’s southern highlands – confirming scientists’ long-standing hypothesis of the Moon’s origin and evolution from a giant ocean of magma which later cooled down.