By firing lasers finer than a human hair at tiny grains of mineral extracted from beach sand, researchers have found an almost four billion-year-old piece of the earth’s crust beneath southern Western Australia.

The discovery has the potential to help explain the planet’s evolution from uninhabitable to life-supporting, according to project leader Maximilian Droellner.

The Curtin University PhD student says the lasers were used to vaporise portions of individual grains of zircon.

This revealed where they were originally eroded from and, in the process, an insight into the geological history of the region.

“There is evidence that an up to four billion-year-old piece of crust about the size of Ireland has been influencing the geological evolution of WA for the past few billions of years,” Mr Droellner said.

He believes the ancient portion of planetary shell has survived multiple mountain-building events between Australia, India and Antarctica, and lies tens of kilometres below ground.

“When comparing our findings to existing data, it appears many regions around the world experienced a similar timing of early crust formation and preservation,” Mr Droellner said.

“This suggests a significant change in the evolution of the earth some four billion years ago, as meteorite bombardment waned, crust stabilised and life on earth began to establish.”

According to earlier studies, part of the research region known as the Yilgarn Craton preserves some of the oldest continental crust on the planet and hosts earth’s oldest terrestrial minerals.

While much of the original geological record is lost to erosion, durable minerals such as zircon form sediments that paint a vivid picture of the planet’s history, according to research supervisor Milo Barham from Curtin’s Timescales of Mineral Systems Group.

Clues to the development of a habitable biosphere, the evolution of continents and the accumulation of mineral resources at ancient plate boundaries are all there to see.

Billions of years of earth’s history is imprinted in the geology of each grain and the work his team is doing is helping unlock that information, Dr Barham says.

“Studying the early earth is challenging given the enormity of time that has elapsed but it has profound importance for understanding life’s significance … and our quest to find it on other planets.”

The piece of WA crust also appears to define an economically important boundary aligned with iron ore and gold deposits.