Chicago Field Museum Scientists Find 'Presolar Grains' of Stardust in Australian Meteorite – It's Now the Oldest Solid Matter Ever Discovered
What is currently the oldest solid material on Earth has just been discovered hiding in an ancient Australian meteorite, according to a report by Forbes. These "presolar grains" of stardust are over 7 billion years old. Our solar system and the Sun, by contrast, are both only 4.5 billion years old. A paper detailing this discovery has just been published in the Proceedings of the National Academy of Sciences.
To date the stardust, scientists could not rely on traditional methods. Instead, researchers say they based its age on neon isotopes produced by galactic cosmic rays. "It starts with crushing fragments of the meteorite down into a powder," explained Jennika Greer, a graduate student from the University of Chicago who works with the Field Museum and co-authored the study. "Once all the pieces are segregated, it's a kind of paste" which, she says, "smells like rotten peanut butter."
These presolar grains contain traces of interstellar dust and are a window into the dawn of time. Based on the analysis of the grains, scientists confirmed an unusually high period of "intense" active star formation around 7 billion years ago. "We now have direct evidence for a period of enhanced star formation. This is one of the key findings of our study," said Dr. Philipp Heck, an associate professor at the University of Chicago, who is a curator at the museum and the lead author of the paper.
The "Murchison meteorite" struck outside the town in Victoria, Australia, in September of 1969. It contains 70 types of alien amino acids, which has made it one of the most-studied meteorites of all time. The Field Museum in Chicago holds one of the largest pieces.
According to Forbes, only 5% of meteorites that fall to Earth contain presolar grains. The fact that we can even hold something in our hands that is 2 billion years older than our own solar system is a bit of a miracle in itself.
"It's so exciting to look at the history of our galaxy," added Heck. "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."
Cover Image: "Dust-rich outflows of evolved stars similar to the pictured Egg Nebula are plausible sources of the large presolar silicon carbide grains found in meteorites like Murchison."
Image courtesy NASA, W. Sparks (STScI) and R. Sahai (JPL). Inset: SiC grain with ~8 micrometers in its longest dimension. Inset image courtesy of Janaína N. Ávila.