The oldest solid material ever found on Earth has been discovered in a meteorite that fell in Australia nearly five decades ago. Researchers at the University of Chicago have been studying the material for about 30 years and recently determined that a sample was about 5 billion to 7 billion years old. Their findings been published in the peer-reviewed Proceedings of the National Academy of Sciences.
Meteorites can act like time capsules of the materials trapped within them. The material that the researchers examined are called presolar grains, or stardust, which are formed when a star dies. Stars are born when gas, dust and heat combine just right and can exist for millions or even billions of years before dying. When it dies, the presolar grains are ejected into space. Presolar grains are extremely rare, found in only about 5 percent of meteorites that have fallen to Earth.
A team of researchers from the U.S. and Switzerland analyzed 40 pre-solar grains contained in a portion of the Murchison meteorite, which fell in Murchison, Victoria in 1969. The researchers used a particular form (isotope) of the element neon – Ne-21 – to measure how long the grains had been exposed to cosmic rays in space. Based on the results, most of the grains had to be 4.6-4.9 billion years old, with the oldest dated around 7.5 billion years old.
Previously, the oldest pre-solar grain dated with neon isotopes was around 5.5 billion years old. For comparison, the Sun is 4.6 billion years old and the Earth is 4.5 billion. Philipp Heck, lead author of the study and associate professor at the University of Chicago, said, “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 [and] the origin of the oxygen we breathe. With stardust, we can trace that material back to the time before the sun.”