Chandrayaan-2 detects possible presence of subsurface ice near south pole of moon
Scientists at the Physical Research Laboratory (PRL), Ahmedabad, used data from the Dual Frequency Synthetic Aperture Radar (DFSAR) aboard Chandrayaan-2 to s...
What Happened
- Scientists at the Physical Research Laboratory (PRL), Ahmedabad, used data from the Dual Frequency Synthetic Aperture Radar (DFSAR) aboard Chandrayaan-2 to study "doubly shadowed" craters at the lunar south pole.
- The study, published in the journal npj Space Exploration (May 2026), examined nine small craters located within larger permanently shadowed regions (PSRs) near the south pole.
- Radar signatures consistent with possible subsurface ice were detected beneath the floors of four craters within the Faustini, Haworth, and Shoemaker crater complexes.
- The strongest evidence of subsurface ice was found in a 1.1-km-wide crater located within the larger Faustini crater.
- Scientists note the findings are significant for future human lunar exploration and the establishment of long-term lunar bases.
Static Topic Bridges
Chandrayaan-2 Mission and the DFSAR Payload
Chandrayaan-2 is India's second lunar mission, launched by ISRO on July 22, 2019, comprising an orbiter, lander (Vikram), and rover (Pragyan). While the lander-rover component did not achieve a soft landing, the orbiter continues to function in a 100-km polar orbit and carries eight scientific payloads.
- The DFSAR (Dual Frequency Synthetic Aperture Radar) is the first fully polarimetric SAR instrument to operate outside Earth orbit.
- It operates in two frequency bands: L-band (24 cm wavelength) and S-band (12 cm wavelength), sharing a common microstrip planar antenna.
- L-band provides deeper penetration of lunar regolith — up to 3–5 metres — enabling detection of subsurface structures.
- Slant-range resolution is selectable from 2 m to 75 m; incidence angle coverage spans 9.5° to 35°.
- The system can operate in standalone (L or S) or simultaneous (both bands) imaging modes with full polarimetric capability.
Connection to this news: The DFSAR's dual-frequency, fully polarimetric design allows it to distinguish ice-related radar backscatter signatures from those of rough rocky terrain — a key challenge that limited previous lunar SAR missions like Chandrayaan-1's Mini-SAR and LRO's Mini-RF.
Permanently Shadowed Regions (PSRs) and Lunar Ice
Permanently shadowed regions are areas of the Moon — predominantly near the poles — that never receive direct sunlight due to the Moon's near-zero axial tilt (~1.54°). Temperatures in PSRs can drop to –230°C, cold enough to trap volatile compounds including water ice over billions of years.
- Water ice in PSRs is thought to have been deposited by cometary impacts and solar wind interactions over geological time.
- "Doubly shadowed" craters are smaller craters nested inside larger PSRs, receiving even less thermal input and thus more likely to retain volatiles.
- The Faustini, Haworth, and Shoemaker craters are well-known large PSR complexes near the lunar south pole, previously studied by NASA's LRO and Chandrayaan-1.
- Water ice on the Moon is a critical resource (In-Situ Resource Utilisation, or ISRU) for future lunar missions — it can be split into hydrogen and oxygen for rocket propellant and used for drinking water.
Connection to this news: The detection of possible subsurface ice in doubly shadowed craters within Faustini strengthens the scientific case for concentrating future landing missions — including India's own Chandrayaan-3, which landed near the south pole in August 2023 — in this region.
India's Lunar Programme — Strategic and Scientific Significance
India's lunar programme spans Chandrayaan-1 (2008), Chandrayaan-2 (2019), and Chandrayaan-3 (2023). Chandrayaan-1's Moon Impact Probe confirmed the presence of water molecules on the lunar surface. Chandrayaan-3's Vikram lander became the first spacecraft to soft-land near the south pole (August 23, 2023), establishing India as only the fourth country to achieve a lunar soft landing.
- Chandrayaan-3 operated for approximately 14 Earth days (one lunar day), confirming the presence of sulphur and other elements near the south pole.
- ISRO's future roadmap includes Chandrayaan-4 (sample return mission) and India's participation in Artemis-adjacent programmes.
- Scientific findings from DFSAR data contribute to global efforts to map ice distribution ahead of crewed lunar missions.
Connection to this news: Chandrayaan-2's DFSAR findings complement Chandrayaan-3's in-situ surface observations, together building a multi-layered picture of the south pole as a resource-rich target for future exploration.
Key Facts & Data
- DFSAR instrument weight: approximately 20 kg
- L-band wavelength: 24 cm; S-band wavelength: 12 cm
- L-band regolith penetration depth: 3–5 metres
- Number of craters studied: 9 doubly shadowed craters in south polar PSRs
- Craters showing ice signatures: 4 (within Faustini, Haworth, Shoemaker complexes)
- Strongest signal: 1.1-km-wide crater inside Faustini crater
- Study published: npj Space Exploration, May 2026
- Chandrayaan-2 launch date: July 22, 2019
- Chandrayaan-3 south pole landing: August 23, 2023
- Moon's axial tilt: ~1.54° (reason for existence of PSRs)