Breaking the ice: Chandrayaan-3 hints at possibility of frozen water beneath Moon's surface

The discovery opens up the possibility of the Moon having many sites in the high latitudes areas closer to the poles harbouring water-ice at shallow depth, making them promising and technically less challenging spots for future lunar exploration and habitation.

New Delhi: Ice may be present a few centimetres below the Moon’s surface in more areas in the polar region than what was previously thought, Indian scientists reported on Thursday using data from Chandrayaan-3 that landed on the satellite two years ago.

The discovery opens up possibility of the Moon having many sites in the high latitudes areas closer to the poles harbouring water-ice at shallow depth, making them promising and technically less challenging spots for future lunar exploration and habitation.

Analysing data from a temperature probe experiment on Chandrayaan-3 Vikram lander, a team led by scientists from Physical Research Laboratory, Ahmedabad found large-scale, highly localised temperature variations between day and night on the lunar surface.

Subsequent modelling studies factoring in such temperature differences suggest that the Moon may have ice just below 10 cm of lunar surface in regions closer to the poles.

The model suggests that slopes facing away from the Sun and towards the nearest pole, with an angle of 14 degrees and beyond may be cool enough for ice to accumulate near the surface.

“Our studies indicate the possibility of having water ice at shallow depth in many locations with a poleward slope where the peak temperature decreases substantially,” Durga Prasad K, PRL scientist and corresponding author of the study, told DH.

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.

The team also having researchers from Vikram Sarabhai Space Centre, Thiruvananthapuram; Andhra University and Space Applications Centre, Ahmedabad suggest that areas on the Moon where ice can form may be more numerous and easier to access than previously thought.

Future long-term exploration (or habitation) of the Moon will likely depend on the availability of ice to provide water, with the likelihood of ice formation in a lunar area directly affected by the surface temperature.

“The study shows that we can’t have global mapping of lunar temperature as local topography makes huge changes. Local topography will play a big role in future lunar missions,”said PRL director Anil Bhardwaj, one of the co-authors of the paper.

“We don’t have to go to the polar regions or permanently shadowed regions in search of water on the Moon.”

The only previous direct measurements of the lunar surface temperature were taken during the Apollo-15 and 17 missions of the 1970s. However, these missions landed near the equator, several thousand kilometres from proposed landing sites for future manned missions, and where terrain slope has little effect on temperature.

Chandrayaan-3, the third Indian lunar mission, had a successful soft landing on the edge of the lunar South Pole (69.3 degrees South latitude), which is called ‘Statio Shiv Shakti’.

Consisting of a Vikram lander and a Pragyan rover, the Indian probe carried six scientific instruments, data from one of which (ChaSTE or Chandra’s Surface Thermophysical Experiment) was used in this study.

The authors found that temperatures at the landing site, a Sun-facing slope angled at six degrees, peaked at 355 Kelvin (82 degrees Celsius) and dropped to 105 Kelvin during the lunar night. A lower peak temperature of 332 Kelvin (59 degrees Celsius) was measured on a flat region approximately one metre from the lander.

“Local topography dictates such variations in surface temperature. We modelled a scenario on what would happen in a pole-ward slope where the peak temperature drops and sub-surface molecules can stay put,” Durga Prasad said.

“The interesting outcome is that the high latitude sites with local slope greater than 14 degrees in poleward direction might offer a similar environment as polar sites for accumulating water ice at shallow depths,” the team reported in Communications Earth and Environment, a journal published by the Nature group.

This is the second major finding from the Chandrayaan-3 mission after last year’s discovery of fresh evidence for a long-standing hypothesis that the entire moon was covered by hot molten rock - a liquid magma ocean - early after its formation.