The Oldest Material Found on Earth: 7 Billion-Year-Old Stardust
Recently, scientists have discovered and identified a 7 billion years old stardust – the oldest material found on our planet.
The stardust was hidden in a massive meteorite that struck Earth in 1969.
In a meteorite that fell more than half a century ago in Australia, scientists have made the grand discovery of stardust that formed about 5 to 7 billion years ago. This makes it the oldest ever found solid material on Earth.
Philipp Heck, the lead author of the study describing the discoveries in the Proceedings of the National Academy of Sciences, shares this was truly inspiring.
“This is one of the most exciting studies I’ve worked on. These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy.”
The professor and his colleagues have examined materials called presolar grains-minerals.
They were formed even before the Sun was born. Heck says they are “solid samples of stars, real stardust”. What’s even more interesting, the meteorites these minerals are trapped in serve as time-capsules. They hold data from the ages before our solar system even existed.
In fact, only about 5% of the meteorites that have struck our planet hold such rare presolar grains. The largest piece of the Murchison meteorite, so named for its landing place in Murchison, Victoria, Australia, is in the Field Museum. For this particular study, researchers at the University of Chicago have isolated presolar grains from the Murchison meteorite about 30 years ago.
Jennika Greer, co-author of the study, breaks down the process with a catchy metaphor:
“It starts with crushing fragments of the meteorite down into a powder. Once all the pieces are segregated, it’s a kind of paste, and it has a pungent characteristic – it smells like rotten peanut butter.“
The scientists figured out the types and the age of the stardust after they isolated the presolar grains.
Philipp Heck explains the methodology they used to clarify how old these minerals were.
“We used exposure age data, which basically measures their exposure to cosmic rays, which are high-energy particles that fly through our galaxy and penetrate solid matter. Some of these cosmic rays interact with the matter and form new elements… By measuring how many of these new cosmic-ray produced elements are present in a presolar grain, we can tell how long it was exposed to cosmic rays, which tells us how old it is.”
With these processes, they found that most of the grains had to be 4.6 to 4.9 billion years old. Moreover, some of them were even older than 5.5 billion years. This makes them much older than the Sun and the Earth.
As for the history this discovery reveals, the researchers believe there was an astral baby boom 7 billion years ago. They figured this out based on the fact that presolar grains are formed after a star dies. In other words, they were born much further back in time.
“With this study, we have directly determined the lifetimes of stardust. We hope this will be picked up and studied so that people can use this as input for models of the whole galactic life cycle.”
Heck believes there are lifetimes’ worth of questions about presolar grains and the early Solar System.
He shares he wishes there were more people involved in learning and discovering more about our home galaxy. Besides, he truly believes astronomy is one of the most interesting things in the world.
“It’s so exciting to look at the history of our galaxy. Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies, the origin of the oxygen we breathe. With stardust, we can trace that material back to the time before the Sun.”