How did Chandrayaan-1 discover water on Moon more than a decade ago?

In 2009, a momentous discovery reshaped our understanding of the Moon, with the Chandrayaan-1 findings coming to light, paving the way for potential future explorations.

Contrary to earlier beliefs that the lunar surface was arid, the Indian Space Research Organisation (ISRO) played an important role in uncovering evidence of water on the Moon.

Now, in 2023, with the successful soft landing of the Chandrayaan-3's Vikram lander which is intended to find more than just water on its mission, we need to revisit this remarkable discovery 14 years later, that paved the way for subsequent lunar missions of not only India but other space powers around the globe.

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Chandrayaan-1

• In October 2008, ISRO's Chandrayaan-1 mission lifted off from Sriharikota on the pioneering journey of studying the moon.
• Although its operational lifespan was intended to be around two years, the mission encountered challenges just ten months into its voyage.
• A star tracker malfunction and thermal shielding issues led to communication disruptions, yet Chandrayaan-1 was deemed a success.

The Moon Impact Probe (MIP) and water discovery

• One of the most significant moments during Chandrayaan-1's mission occurred on November 14, 2008, when the Moon Impact Probe (MIP) detached from the orbiter and struck the lunar south pole near the Shackleton crater.
• The controlled impact unveiled a revelation: the presence of water ice on the Moon's surface.
• During its descent, the MIP's Chandra’s Altitudinal Composition Explorer (CHACE) recorded readings providing compelling evidence of water.

Dispute over water discovery

• Shortly after the news broke, a dispute arose between ISRO and NASA.
• On September 24, 2009, NASA claimed that its Moon Mineralogy Mapper (M3) instrument, also on board the Chandrayaan orbiter, had detected lunar water from orbit.
• ISRO countered by asserting that its Moon Impact Probe (MIP) had made the discovery three months earlier but had refrained from announcing it until NASA's confirmation.

A decade later

• Many years later, in 2017, NASA employed a ground-based radar to locate Chandrayaan-1, along with its own Lunar Reconnaissance Orbiter (LRO).
• The orbiter was found to be orbiting the Moon at an altitude of 160 km.
• NASA's M3 instrument reanalysed its data, confirming the presence of water in shaded areas of lunar craters near the poles, presumably because this area receives less intense or no sunlight.
• This is what reaffirmed the importance of Chandrayaan-1's findings.

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ISRO's Chandrayaan-1 mission, despite its share of challenges and setbacks, left an indelible mark on lunar exploration by discovering water on the Moon's surface. As we commemorate this discovery 14 years later, it stands tall as a testament to India's pioneering contributions to space exploration.