In 1969, Australia recovered the Murchison meteorite after it fell near Victoria. Years later, scientists studied stardust hidden inside and discovered grains dating back roughly 7 billion years, before the Solar System existed

A tiny grain buried inside the Murchison meteorite is older than the Sun, older than Earth, and older than the solar system itself. Scientists estimated that some of the meteorite’s presolar grains formed between 5 and 7 billion years ago, with the oldest material dating to roughly 7 billion years. That makes these microscopic grains the oldest solid material ever identified on Earth.

The story begins on September 28, 1969, when the Murchison meteorite broke apart in the atmosphere over Victoria, Australia. Pieces fell across an area of roughly 35 square kilometers near the town of Murchison, and about 108 kilograms of material were eventually recovered. More than five decades later, samples from that same fall are still being studied because they contain material that predates the birth of our solar system.

The meteorite is not 7 billion years old

There is an important detail that often gets lost in the headline. The Murchison meteorite itself is not 7 billion years old. It is a carbonaceous chondrite that formed from material in the early solar system, but trapped inside it are much older grains that existed before the Sun was born.


Those grains are called presolar grains, because they formed before the solar system existed. They are essentially pieces of ancient stardust that survived the formation of the Sun, planets and asteroids and were eventually locked inside primitive meteorites such as Murchison. The seven-billion-year figure applies to those individual grains, not to the meteorite as a whole.

A grain smaller than a speck of dust

The material studied by scientists was extraordinarily small. Researchers examined grains of silicon carbide, a mineral that can be only a few micrometers across. A human hair is typically tens of micrometers wide, so these grains are far too small to identify by simply looking at a piece of meteorite.

That tiny size is part of what makes the discovery so remarkable. A grain that spent billions of years traveling through space was eventually trapped inside a meteorite, survived the violent process that created the early solar system, and then survived another journey through Earth's atmosphere before scientists finally isolated it in a laboratory.

Scientists had to dissolve the meteorite to find it

Finding the ancient grains was not a matter of opening the meteorite and picking them out. Researchers first crushed samples of Murchison and used chemical treatments to remove much of the surrounding material. The silicon-carbide grains were resistant to the process, allowing scientists to separate them from the rest of the meteorite.

The research team, led by Philipp Heck, a cosmochemist at the Field Museum and associate professor at the University of Chicago, then studied the surviving grains. Their findings were published in January 2020 in the Proceedings of the National Academy of Sciences. The work focused on how long the grains had traveled through interstellar space before becoming part of the material that eventually formed our solar system.

The age was hidden in the atoms

The researchers did not determine the grains' ages simply by measuring the age of the silicon carbide itself. Instead, they looked at changes caused by cosmic rays, high-energy particles that travel through space and strike exposed matter.

When cosmic rays hit a grain, nuclear reactions can create new isotopes inside it. By measuring those isotopes, scientists can estimate how long the grain was exposed to cosmic radiation. That provided a way to reconstruct part of the grain's journey before it became trapped in the material that formed the young solar system.

The results revealed a surprisingly wide range of ages. Some of the grains were roughly 5 billion years old, while others reached about 7 billion years. The oldest therefore existed billions of years before the Sun began forming, giving scientists a physical sample of material from an earlier chapter of the Milky Way.

These grains came from stars that died long ago

Presolar grains are not random pieces of space dust. Their chemical signatures show that many formed around stars that had reached late stages of their lives and were releasing material back into space.

As those stars shed gas and dust, minerals could form in the material flowing away from them. Some of those microscopic particles eventually entered the interstellar medium, where they remained for an enormous amount of time before becoming incorporated into the cloud that gave rise to our solar system.

That means the Murchison grains preserve a history that cannot be reconstructed from the planets alone. They carry evidence from stars that existed before the Sun, allowing scientists to examine actual material produced during an earlier period of galactic history.

Why the Murchison meteorite matters so much

Murchison has been unusually valuable because scientists recovered a large amount of it after the 1969 fall. Museums Victoria records the meteorite as a CM2 carbonaceous chondrite and lists the total recovered weight at about 108 kilograms. More than 80 kilograms of the material is held in scientific collections, according to the museum's collection information.

The meteorite also contains other material that makes it important to researchers studying the early solar system. Its primitive chemistry has allowed scientists to investigate organic compounds and other components that were present in the material from which planets eventually formed.

That is why Murchison continues to appear in scientific research decades after it landed in Victoria. Scientists do not have to travel to another star to study ancient stellar material. Some of that material was delivered to Earth in a rock that fell into a rural part of Australia in 1969.

What this discovery tells us about the Sun

The oldest grains also give researchers a way to investigate what the Milky Way was doing before our solar system formed. The 2020 study found evidence for a population of grains that had spent different amounts of time in interstellar space, including a group that suggested increased star formation before the Sun's birth.

That matters because the Sun did not form in isolation. It was created from a cloud of gas and dust that already contained material produced by previous generations of stars. Some of that ancient material became part of the planets, asteroids and meteorites that formed afterward.

The Murchison grains are therefore more than an age record. They are physical leftovers from an earlier generation of stars, preserved inside a solar-system rock and available for scientists to examine in a laboratory.

The strangest part is how ordinary the discovery looks

There is something almost easy to miss about the story. The ancient material is not a giant alien object or a spectacular piece of metal. It is a microscopic grain of silicon carbide that cannot be seen without specialized equipment.

Yet that tiny grain survived for billions of years before becoming part of the solar system. It then spent roughly 4.6 billion years inside or around the young solar system before the Murchison meteorite eventually brought it to Earth.

For scientists, that is the real value of the discovery. A small piece of stardust can preserve information from a time when the Sun did not exist, Earth did not exist, and none of the familiar planets had formed.