India's space agency landed a spacecraft on the moon's south pole on Wednesday, a mission that will advance the country's space ambitions and expand knowledge of lunar ice, potentially one of the moon's most valuable resources.

Here's what's known about the presence of frozen water on the moon - and why space agencies and private companies see it as a key to a moon colony, lunar mining and potential missions to Mars.

India's much-awaited moon mission Chandrayaan-3 has been scheduled for launch on July 14, 2023. The Soviet Union, the United States, and China are the only three countries that have successfully carried out soft landings on the moon.

HOW DID SCIENTISTS FIND WATER ON THE MOON?

As early as the 1960s, before the first Apollo landing, scientists had speculated that water could exist on the moon. Samples the Apollo crews returned for analysis in the late 1960s and early 1970s appeared to be dry.

In 2008, Brown University researchers revisited those lunar samples with new technology and found hydrogen inside tiny beads of volcanic glass. In 2009, a NASA instrument aboard the Indian Space Research Organisation's Chandrayaan-1 probe detected water on the moon's surface.

In the same year, another NASA probe that hit the south pole found ice below the moon's surface. An earlier NASA mission, the 1998 Lunar Prospector, had found evidence that the highest concentration of ice was in the south pole's shadowed craters.

If ice exists in sufficient quantities, it could be a source of drinking water for moon exploration and could help cool equipment.

It could also be broken down to produce hydrogen for fuel and oxygen to breathe, supporting missions to Mars or lunar mining.

WHAT MAKES THE SOUTH POLE ESPECIALLY TRICKY?

Attempted landings on the moon have failed before. Russia's Luna-25 craft had been scheduled to land on the south pole but spun out of control on approach and crashed on Sunday.

The south pole - far from the equatorial region targeted by previous missions, including the crewed Apollo landings - is full of craters and deep trenches.

Both the United States and China have planned missions to the south pole.