Did Chandrayaan-2 Find Buried Water Ice at the Lunar South Pole?

The Short Answer

Yes — India’s Chandrayaan-2 spacecraft used its DFSAR radar instrument to detect signatures of buried water ice inside doubly shadowed craters at the lunar south pole, craters so cold they rank among the coldest naturally occurring places in the entire inner solar system.

What Are Doubly Shadowed Craters?

Most people have heard of permanently shadowed regions on the Moon — areas that never receive direct sunlight because of the Moon’s near-zero axial tilt. Doubly shadowed craters take this a step further. They are pockets nested inside permanently shadowed regions, shielded not only from direct sunlight but also from the scattered and reflected light that faintly illuminates their surroundings. The result is an environment of extraordinary darkness and cold. Temperatures inside these craters plunge to approximately 25 Kelvin — roughly minus 248 degrees Celsius — making them colder than the surface of Pluto and among the most frigid spots found anywhere in the inner solar system.

How Did the DFSAR Radar Work?

Chandrayaan-2’s Dual-frequency Synthetic Aperture Radar, known as the DFSAR, operates at two distinct radio frequencies. Unlike optical cameras that photograph a surface, radar instruments transmit microwave signals that penetrate below the surface and measure what bounces back. When scientists analyzed the return signals from multiple south polar craters, they found anomalously high circular polarization ratios — a specific pattern in how the radar waves scattered back. This pattern is a well-established signature of water ice, the same type of signal detected in icy environments elsewhere in the solar system. The fact that DFSAR performed with this level of sensitivity surprised many in the scientific community and elevated Chandrayaan-2’s legacy well beyond its initial mission challenges.

How Old Is the Ice and Where Did It Come From?

The water ice locked beneath the lunar south pole is believed to have accumulated over three to four billion years of bombardment by comets and water-bearing asteroids. As these objects struck the Moon, they delivered volatile compounds including water. Because the doubly shadowed craters never warm enough for ice to sublimate, the water molecules that migrated into these cold traps became permanently frozen. This means the ice is not merely a resource — it is a frozen chemical record of the early solar system, potentially preserving organic molecules and isotopic signatures that could reveal the history of water delivery across the inner planets, including Earth.

Why Does This Matter for Space Exploration?

Buried lunar water ice at the south pole has profound implications for humanity’s future in space. Water can be split into hydrogen and oxygen through electrolysis, producing the two components of cryogenic rocket propellant. A crewed lunar base situated near extractable ice deposits could theoretically manufacture its own fuel, transforming the Moon from a destination into a refuelling depot for missions deeper into space — including crewed expeditions to Mars. Drinking water and life support systems would also benefit directly. Several space agencies and private companies are already designing missions around the assumption that polar ice exists in extractable quantities. Chandrayaan-2’s radar data provides some of the strongest sub-surface evidence yet that this assumption is well-founded.

What Comes Next?

India’s Chandrayaan-3 mission successfully landed near the lunar south pole in August 2023, and NASA’s Artemis program is explicitly targeting the same region. Future missions equipped with drilling hardware and in-situ resource utilization technology may attempt to access and analyze the ice directly. If confirmed in accessible quantities, the buried water ice detected by Chandrayaan-2 could represent one of the most consequential resource discoveries in the history of space exploration.