Chandrayaan-2 finds 'possible presence' of ice in lunar south pole

Editorial Lens

"The Chandrayaan-2 mission, through its advanced Dual Frequency Synthetic Aperture Radar (DFSAR), has provided breakthrough evidence of subsurface water-ice within 'doubly shadowed craters' in the Lunar South Polar Region. Unlike surface frost, this ice is sequestered in micro-craters shielded from both direct sunlight and reflected thermal radiation, maintaining extreme stability at temperatures as low as 25 K. This discovery marks a critical transition in lunar science from mere observation to the practical implementation of In-Situ Resource Utilization (ISRU). Strategically, the identification of these stable ice deposits transforms the Moon into a potential logistical gateway for deep-space exploration. By utilizing electrolysis to convert water into liquid hydrogen and oxygen, the Moon could serve as a vital refueling station for Mars missions. For India, this scientific milestone provides significant geopolitical leverage in the emerging 'space commons' debate, as the race for lunar resource governance intensifies between major space powers like the US (Artemis Accords) and China (ILRS)."

Syllabus Mapping: * GS Paper III: Science and Technology—developments and their applications and effects in everyday life; Achievements of Indians in science & technology; Awareness in the fields of Space.

Context

Nearly seven years after its launch in July 2019, India's Chandrayaan-2 Orbiter continues to deliver breakthrough planetary data. In May 2026, scientists from the Physical Research Laboratory (PRL) in Ahmedabad published strong evidence confirming the presence of subsurface water-ice hidden within unique "doubly shadowed craters" in the Lunar South Polar Region.

By analyzing radar imagery from the orbiter's Dual Frequency Synthetic Aperture Radar (DFSAR) payload, the discovery provides high-fidelity targets for future crewed habitations and In-Situ Resource Utilization (ISRU) frameworks.

1. Scientific Definitions: PSRs vs. Doubly Shadowed Craters

Understanding the lunar environment requires distinguishing between different degrees of solar shielding at the poles:

• Permanently Shadowed Regions (PSRs): Due to the Moon’s very slight axial tilt (just $1.5^\circ$), the rims of deep polar craters permanently block direct sunlight from reaching their floors. These areas serve as cosmic cold traps, preserving volatile elements for billions of years.
• Doubly Shadowed Craters: These are micro-craters located inside larger, already existing PSRs. They are unique because they are shielded not only from direct sunlight but also from the reflected thermal radiation bounced off nearby illuminated hills. This double insulation creates some of the coldest environments in the Solar System, with temperatures plunging to $25\text{ K}$ (approximately $-248^\circ\text{C}$), keeping buried ice deposits structurally stable.

2. Technical Mechanics of Detection: The DFSAR Advantage

Because standard optical cameras cannot capture images in permanent darkness, scientists rely on microwave remote sensing payloads:

• Fully Polarimetric Radar: The DFSAR is the first fully polarimetric synthetic aperture radar sent to orbit the Moon. Operating across both L-band and S-band microwave frequencies, it can penetrate deep into the loose lunar soil (regolith).
• The Polarization Signature Matrix: To distinguish actual subsurface ice from rough, rocky terrain (which can fool standard radar), the PRL team established a refined polarimetric filter: