'Oldest solid material' discovered in meteorite that fell to Earth fifty years ago

A meteorite contains the oldest material on Earth – 7-billion-year-old stardust Credit: NASA/W Sparks/R Sahai/PA

Scientists have discovered what is believed to be the oldest solid material ever found.

Stardust, formed up to seven billion years ago, has been unearthed from the Murchison meteorite that fell in Victoria, Australia, in 1969.

The scientific name for the materials examined in the study is "presolar grains-minerals" - tiny particles that formed before the sun was born.

The Murchison meteorite landed on 28 September 1969 in Victoria, Australia. Credit: James St. John/Flickr

Before finding its way to earth, the material was created when stars form in a process where dust and gas collapse in on each other and heat up.

After burning for millions of years, the star eventually dies and throws particles made in their formation out in to space.

Those bits of stardust go on to eventually form new stars, planets, moons, and meteorites - like the one that fell to earth in 1969.

NASA’s Solar Dynamics Observatory captures a 'solar flare' from the sun. Credit: NASA/SDO

Lead author on the study, Professor Philipp Heck said the discovery helps "tell us how stars formed in our galaxy".

“They’re solid samples of stars, real stardust,” said Prof Heck.

The researchers suggest that seven billion years ago, there was a bumper crop of new stars forming.

The tiny presolar grains uncovered from the Murchison meteorite are rare, however, and are only found in about 5% of the meteorites that have fallen to earth.

The grains for this study were isolated from the Murchison meteorite about 30 years ago at the University of Chicago by crushing fragments of it into powder.

Scientists took electron microscope photos to be able to see the grains - this one is about the size of a red blood cell. Credit: Janaína N. Ávila

Jennika Greet is a co-author of the study, published in Proceedings of the National Academy of Sciences, and explains how the stardust was extracted:

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

This "paste" was then dissolved with acid, until only the presolar grains remained.

Researchers compared the process to burning down a haystack to find the needle.

The central star in the Egg Nebula is casting away shells of gas and dust. Credit: NASA/ESA/The Hubble Heritage Team STScI/AURA

By measuring how many of the new cosmic-ray produced elements are present in a pre-solar grain, scientists can tell how long it was exposed to cosmic rays - telling them how old it is.

The researchers learned that some of the presolar grains in their sample were the oldest ever discovered on Earth.

Based on how many cosmic rays they had soaked up, most of the grains had to be 4.6 to 4.9 billion-years-old, and some grains were older than 5.5-billion-years.