The dark blotches, called maria, are the result of a series of volcanic eruptions that occurred billions of years ago, covering the surface in hot lava.

The remnants of these ancient volcanos may be the key to providing a water source for astronauts in the future.

While the Moon lacks bodies of liquid water, new research from the University of Colorado Boulder (US) has used computer modelling to predict that these volcanos likely left behind huge sheets of ice on the Moon's poles, which could potentially be several hundred metres thick.

This research, published in The Planetary Science Journal, drew on computer simulations to recreate conditions on the Moon from 2-4 billion of years ago, when tens of thousands of immense volcanoes were erupting.

From these models they determined that the ancient Moon volcanoes likely gave out enormous amounts of carbon monoxide and water vapour, which potentially created thin layers of atmosphere that would have lasted long enough (around 2500 years) to form longer-lasting sheets of ice.

"The atmospheres escaped over about 1,000 years, so there was plenty of time for ice to form," says Andrew Wilcoski, lead author.

"We envision it as a frost on the Moon that built up over time."

According to the model's estimates, roughly 41 per cent of the water vapour from the volcanoes could have condensed into ice on the Moon's surface, and may now be concealed within craters, waiting to be discovered.

This is over eight trillion tonnes of ice.

"It's a potential bounty for future Moon explorers who will need water to drink and process into rocket fuel," says co-author Paul Hayne.

"It's possible that 5 or 10 metres below the surface you have big sheets of ice."

This lunar ice may be difficult to uncover, as it's likely buried under several metres of lunar dust.

But now that we know where it might be, all we have to do is start digging.