Direct measurements taken by India’s Chandrayaan-3 lunar lander may have confirmed that ice exists just a few centimetres beneath the Moon’s surface.

The results of an experiment, published in Communications Earth & Environment, could aid in future crewed long-term missions or habitation of the Moon which will likely rely on local sources of water.

In 2018, India’s Chandrayaan-1 spacecraft was the first to provide definitive proof of water ice on the Moon using its orbital mapping instruments. This ice is on the surface. But water ice just beneath the surface further away from the poles may also be useful for crewed missions.

Chandrayaan-3’s Vikram lander touched down on the lunar surface at about 69° south – the equivalent latitude on Earth crosses Antarctica. This means it landed in a prime location to investigate the potential for water ice in regions away from the poles.

It’s believed that ice can only form this close to the surface in the lunar polar regions due to large variations in surface temperature.

The only direct measurements of the Moon’s surface temperature, however, were taken by the Apollo missions in the 1970s, thousands of kilometres away from the polar regions.

Analysis of readings of the surface temperature and 10cm shows favourable conditions for ice to form.

Chandrayaan-3’s ChaSTE – a temperature probe on the Vikram lander – showed that a Sun-facing slope of 6° peaked at 82°C and dropped to –168°C overnight. Just 1m away, a flat region registered a much lower peak temperature of 59°C.

Data collected by the lander was used to develop a model of how slope angle affects surface temperature at polar latitudes on the Moon.

The model showed that ice could accumulate close to the surface if a slope is facing away from the Sun, toward the nearest pole and has an angle greater than 14°.

These conditions are similar to those at the lunar poles, including the proposed landing sites for NASA’s crewed Artemis missions.