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Scientists from the Physical Research Laboratory (PRL) have detected the possible presence of subsurface water ice in the doubly shadowed craters of the lunar south pole. This discovery was made using data from the Dual Frequency Synthetic Aperture Radar (DFSAR) payload on 's Chandrayaan-2 orbiter, providing crucial insights for future lunar exploration and resource utilization missions.
The discovery of potential subsurface water ice hinges on the advanced capabilities of the Dual Frequency Synthetic Aperture Radar (DFSAR) payload aboard the Chandrayaan-2 orbiter. DFSAR uses active microwave remote sensing, allowing it to penetrate the lunar regolith (soil) and distinguish between rough rocky surfaces and actual volumetric scattering caused by ice. The study introduces a refined radar-based metric combining Circular Polarization Ratio (CPR) and Degree of Polarization (DOP) to confidently identify these ice signatures. High CPR combined with low DOP indicates that the radar signal is interacting with subsurface ice rather than just bouncing off rocks. This technological success highlights India's growing self-reliance in developing sophisticated space instrumentation and emphasizes the continuing scientific value of the Chandrayaan-2 orbiter, even after the loss of the Vikram lander.
The focus of this research is on doubly shadowed craters located within the Permanently Shadowed Regions (PSRs) near the lunar south pole. Due to the moon's very small axial tilt (about 1.5 degrees), sunlight never reaches the bottoms of these deep craters at the poles. These regions act as cold traps, maintaining extremely low temperatures (around -25K or -248°C), making them ideal environments for preserving lunar polar volatiles, particularly water ice, over geological timeframes. The identification of a specific crater within the Faustini crater, exhibiting a lobate-rim morphology (a flow-like appearance suggesting an impact penetrated an ice layer), provides compelling geological evidence supporting the radar data. Understanding the distribution of these resources is crucial for unraveling the history of water in the inner solar system.
The confirmation of accessible subsurface water ice has profound strategic implications for future space exploration. Water is heavy and expensive to launch from Earth; therefore, In-Situ Resource Utilization (ISRU) is critical for sustainable long-term human presence on the moon. Lunar water can be purified for drinking, used for radiation shielding, or broken down into hydrogen and oxygen to produce rocket propellant. This makes the lunar south pole a highly sought-after destination for future missions, including NASA's Artemis program and India's own future lunar endeavors. India's early identification of these potential resource hotspots strengthens its position in international space diplomacy and potential collaborations, while also paving the way for eventual missions aimed at establishing a continuous lunar base.