Global Map of Water on the Moon
Science & Technology › Space Technology and ISRO · Topic 12.27
For a long time the Moon was thought to be dry, but missions since the 1990s have found water, mostly as ice in permanently shadowed craters near the poles and as small amounts of hydroxyl and water molecules bound to the surface soil. India's Chandrayaan-1 carried NASA's Moon Mineralogy Mapper, which detected hydroxyl and water signatures across the surface in 2009. NASA's LCROSS impact in 2009 found water in a crater plume, the stratospheric telescope SOFIA found molecular water in sunlit Clavius crater in 2020, and Chandrayaan-2 data helped to confirm water ice and hydroxyl. Scientists use these data to produce global maps of where lunar water might be, which guide landing sites for future missions, since water can provide drinking water, oxygen and rocket fuel.
5 min read · UPSC Prelims · Science & Technology · Space Technology and ISRO
At a Glance
- First strong detection Chandrayaan-1 M3, 2009
- Ice location Polar shadowed craters
- Other evidence LCROSS, SOFIA, Chandrayaan-2
- Uses Water, oxygen, fuel
- Target region South pole
- Exam link UPSC Prelims, Science & Technology: Space Technology and ISRO
Where Does It Fit?
This topic follows the account of Cassini and OSIRIS-REx. It returns to the Moon and ties together the findings of the Indian lunar missions with those of other agencies on the presence of water. Previous topic: Cassini Mission to Saturn and OSIRIS-REx Mission to Asteroid Bennu. Next topic: Indigenously Developed S-Band Doppler Weather Radar.
How Was Lunar Water Found?
| Evidence | Details |
|---|---|
| Apollo samples | Rocks returned from 1969 to 1972 appeared dry, so the Moon was long thought to be anhydrous |
| Clementine and Lunar Prospector | Radar and neutron data in the 1990s hinted at hydrogen, possibly water ice, at the poles |
| Chandrayaan-1 and M3 | NASA’s Moon Mineralogy Mapper on India’s Chandrayaan-1 detected absorption features of hydroxyl and water across the surface, announced in September 2009. Its Mini-SAR radar also found ice-like signatures in polar craters |
| LCROSS | NASA’s mission in October 2009 crashed a rocket stage into the crater Cabeus and found water in the plume of debris |
| SOFIA | The airborne Stratospheric Observatory for Infrared Astronomy found molecular water in sunlit Clavius crater, reported in October 2020 |
| Chandrayaan-2 | Its orbiter instruments gave stronger detection of hydroxyl and water, and a dual-frequency radar mapped ice-bearing areas |
| Chandrayaan-3 | Its lander measured the temperature profile of the polar surface and found sulphur, which helps in understanding the south polar soil |
Where Is the Water and What Is It Good For?
- Permanently shadowed regions: deep craters near the poles that never receive sunlight, with temperatures near minus 230 degrees Celsius, which can keep ice for billions of years
- Surface hydration: thin layers of hydroxyl and water in the top layer of soil, formed when solar wind protons react with oxygen in minerals
- Drinking water: ice can be melted for use by astronauts
- Breathable air: water can be split by electrolysis into oxygen to breathe
- Rocket fuel: hydrogen and oxygen from water make rocket propellant, so the Moon could serve as a refuelling station
- Reduced launch cost: using Moon resources saves bringing mass from Earth
- Science: the ice records how water came to the inner solar system
- Competition: many agencies plan to land near the south pole, including Artemis missions and Chinese and Indian plans
What Else Should You Remember?
- Global maps: maps are built from orbiter data on hydrogen, temperature, radar and infrared light to show where water ice is likely at the poles, and where hydration is seen at lower latitudes
- Chandrayaan-1 Moon Impact Probe: ISRO’s probe crashed near the Shackleton crater at the south pole on 14 November 2008 and measured water vapour in the thin lunar atmosphere
- NASA VIPER: a planned rover to search for ice at the south pole, cancelled by NASA in 2024
- Chang’e 5: China’s sample return mission in 2020 found small amounts of water in lunar soil
- Chang’e 7: China’s planned south pole mission
- LUPEX: a planned joint ISRO and JAXA mission, Chandrayaan-5, with a rover to measure water at the pole
- Hydroxyl versus water: hydroxyl is a chemical group with one hydrogen and one oxygen atom, and it is not the same as molecular water
- Amounts: the amounts are small compared with Earth, and the exact quantities remain uncertain
- Legal frame: the Outer Space Treaty bars national ownership of the Moon, but use of resources is debated under the Artemis Accords
- India’s lunar missions: see Chandrayaan Missions (Chandrayaan-I, II, III) and the Mars Orbiter Mission
- Day and night: the temperature at the south pole varies sharply between sunlit and shadowed areas
- Caution: the exact size of ice deposits is still being studied, so exam answers should avoid specific volumes
Why Does It Matter for the Exam?
- Instruments and missions: M3 on Chandrayaan-1, LCROSS, SOFIA
- Concept: permanently shadowed regions
- Uses: water, oxygen, fuel
- Current affairs link: south pole missions and Artemis
- Common errors: saying that Chandrayaan-3 first discovered water on the Moon
As an analytical point, finding water changed the Moon from a destination for visits to a possible base. India’s data from Chandrayaan-1 started this change, and its later missions aim to measure the ice on site.
Why Is This Topic Important?
- Detections Who found what
- Place Shadowed craters
- Use Moon base
What Came Next?
The next topic covers the indigenously developed S-band Doppler weather radar. Next topic: Indigenously Developed S-Band Doppler Weather Radar.
Key People and Terms
- PSR Permanently shadowed region
- Hydroxyl One oxygen and one hydrogen
- M3 Moon Mineralogy Mapper
- LCROSS Impact mission 2009
- Regolith Loose lunar soil
- Volatiles Easily vaporised substances
Exam Corner
Points to Remember
- M3 detection: announced September 2009.
- LCROSS impact: October 2009.
- SOFIA found water in Clavius crater (2020).
- PSR temperature: near minus 230 degrees Celsius.
- Moon Impact Probe: 14 November 2008.
Do Not Confuse With
- Hydroxyl and water Chemical group versus molecule
- Surface hydration and polar ice Thin layer widely versus thick deposits in craters
- M3 and ChaSTE Mineral mapper on Chandrayaan-1 versus temperature probe on Chandrayaan-3
Memory Hook
Apollo found it dry; M3 said hydroxyl, LCROSS splashed it, SOFIA saw it in the sun.
Mains Angle
Questions ask for missions and instruments. These points help.
- Evidence Many missions
- Importance Resources
- India M3 and Chandrayaan
A Question You May Face
An original practice question, not a past paper question.
“Discuss the evidence for water on the Moon and its importance for future space exploration, with reference to India’s lunar missions.”
How to Answer
- Evidence M3, LCROSS, SOFIA.
- Where Polar craters.
- Uses Water, fuel.
- India Chandrayaan-1, 2, 3.
GS Relevance
Frequently Asked Questions
Who first found water on the Moon?
Water signatures on the Moon were first clearly detected in 2009 by the Moon Mineralogy Mapper, a NASA instrument on India's Chandrayaan-1, which found hydroxyl and water molecules across the lunar surface. NASA's LCROSS mission confirmed water in a polar crater plume in October 2009, and later missions added more evidence.
Where is the water on the Moon?
Most of the water ice is thought to lie in permanently shadowed craters near the lunar poles, where sunlight never reaches and temperatures stay near minus 230 degrees Celsius. Thin layers of hydroxyl and water are also found in the top soil at many latitudes, formed by interaction of the solar wind with minerals.
Why is water on the Moon important?
Water on the Moon could give drinking water and oxygen to astronauts and could be split into hydrogen and oxygen to make rocket fuel. This would reduce the cost of supplying a base from Earth and let the Moon work as a refuelling station for missions deeper in the solar system.
What did SOFIA discover about lunar water?
The Stratospheric Observatory for Infrared Astronomy, a telescope carried on an aircraft, detected molecular water in the sunlit Clavius crater of the Moon, as reported in October 2020. This showed that water can exist outside the cold shadowed regions, perhaps trapped in glass beads or in the soil.
What is LUPEX?
LUPEX, the Lunar Polar Exploration mission, is a planned joint mission of ISRO and the Japan Aerospace Exploration Agency, also known as Chandrayaan-5. It will land a rover near the lunar south pole to measure the amount and form of water in the soil, building on the results of the earlier Chandrayaan missions.
PYQ Practice — Statement Analysis
1 Chandrayaan-1 carried the Moon Mineralogy Mapper that detected hydroxyl and water.
A NASA instrument.
2 Most lunar water ice is thought to be in permanently shadowed craters near the poles.
Where it is extremely cold.
3 SOFIA found water in the sunlit Clavius crater.
Reported in 2020.
4 Chandrayaan-3 was the first mission to find water on the Moon.
Earlier missions found it.
Past Mains Questions on This Topic
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