How India’s Chandrayaan-1 Found Water on the Moon
published during a waning crescent moon.
10/25/2016

Chandrayaan-1

Credit: ISRO

It wasn’t the second, tenth, or even twentieth mission to the moon. With our only natural satellite already conquered, an endeavor like India’s lunar satellite is usually buried a few paragraphs in textbooks, far below the dozens of crafts that preceded it. But Chandrayaan-1 — India’s first ever rendezvous with the moon — was the little probe that could, and did, find evidence of water molecules on the moon’s surface.

Though the lunar orbiter below looks like it was made from parts of a Windows 95 screensaver, Chandrayaan-1 was actually a sophisticated patchwork of international bits and pieces from India, Germany, the United States and the United Kingdom, among others. Designed to hobnob with the moon for two years, the Indian Space Research Organization (ISRO)’s $57 million baby launched in late 2008.

Hovering at a height of 100 kilometers from the lunar surface, Chandrayaan-1 carefully scanned the moon’s chemical and mineral composition. China’s Chang’e 1 craft was the last to stop by before India’s satellite arrived, both with destinies that included mapping a three-dimensional atlas.

But the ISRO pinned evidence of a secret that astronomers suspected the moon was keeping: water. Forty years earlier, Apollo astronauts had brought back moon rocks, too. Upon analysis, water was actually found present in the samples, but the water’s origins were deemed an accidental contamination from Earth materials, according to Space.com. Though the leak was disappointing, the moon’s makeup was strikingly similar to Earth’s, and finding water-ice steadily became the holy grail for lunar scientists.

Chandrayaan-1

Credit: NASA/JPL-Caltech

Fast-forward to the late ‘90s, when researchers largely supported the hypothesis that the moon formed when an impactor named Theia collided with an early Earth, leaving the moon a molten hellscape. Based on the composition of the moon’s skin, the magma ocean crystallized, with rocks lower in density floating upward to form the crust. Iron, though sunk to the bottom, which is thought to compose the moon’s innards, and volcanos may have blasted lava all over the surface. Meanwhile, in 1999, Cassini flew by the moon and suspected water (H2O) and hydroxyl (OH) were on the surface.

Chandrayaan-1

Credit: ISRO/NASA/JPL-Caltech/USGS/Brown Univ.

The H2O minerals shown around the small crater above are associated with material ejected from it — but the results weren’t published until Chandrayaan-1’s Moon Mineralogy Mapper observed water molecules decades later. Soon other vehicles riddled with data like asteroid maven Deep Impact and comet chaser EPOXI chimed in to report the same findings.

The three-color composite below is of the sun’s near-infrared radiation. The blue signifies water-ice deposits, which were found in the bases of craters on the moon’s far side that’s in permanent shadow. The other major discovery was the presence of hydroxyl (OH) on the surface.

Chandrayaan-1

Credit: ISRO/NASA/JPL-CalTech/Brown Univ./USGS

After more than 3,400 orbits, the Chandrayaan-1 spacecraft ran into trouble. Despite a successful hard landing of the Moon Impact Probe, communication with the satellite was lost nearly a year after its launch. But it did drop mounds of evidence on us back on Earth by validating the existence of water, as well as the lunar magma ocean hypothesis. Chandrayaan-1’s legacy continues as countries such as China continue to prod the moon’s icy poles for lunar answers.