Discover the oldest material known to exist on earth.

Scientists analysing a meteorite have discovered the oldest material known to exist on Earth.##

More to be found

Dr Heck told BBC News: "Only 10% of the grains are older than 5.5 billion years, 60% of the grains are "young" (at) 4.6 to 4.9 billion years old, and the rest are in between the oldest and youngest ones.

"I am sure there are older pre-solar minerals in Murchison and other meteorites, we just haven't found them yet."

Previously, the oldest pre-solar grain dated with neon isotopes was around 5.5 billion years old.

The findings shed light on a debate over whether or not new stars form at a steady rate, or whether there are highs and lows in the number of new stars over time.

"Thanks to these grains, we now have direct evidence for a period of enhanced star formation in our galaxy seven billion years ago with samples from meteorites. This is one of the key findings of our study," said Dr Heck.

The researchers also learned that pre-solar grains often float through space stuck together in large clusters, like granola. "No one thought this was possible at that scale," Philipp Heck explained..

Scientists analysing a meteorite have discovered the oldest material known to exist on Earth.##

They found dust grains within the space rock - which fell to Earth in the 1960s - that are as much as 7.5 billion years old.

The oldest of the dust grains were formed in stars that roared to life long before our Solar System was born.

A team of researchers has described the result in the journal Proceedings of the National Academy of Sciences.

When stars die, particles formed within them are flung out into space. These "pre-solar grains" then get incorporated into new stars, planets, moons and meteorites.

"They're solid samples of stars, real stardust," said lead author Philipp Heck, a curator at Chicago's Field Museum and associate professor at the University of Chicago.

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A team of researchers from the US and Switzerland analysed 40 pre-solar grains contained in a portion of the Murchison meteorite, that fell in Australia in 1969.

"It starts with crushing fragments of the meteorite down into a powder," said co-author Jennika Greer, from the Field Museum and the University of Chicago.

"Once all the pieces are segregated, it's a kind of paste, and it has a pungent characteristic - it smells like rotten peanut butter."