Scientists have discovered ancient microscopic dust grains from a meteorite, which were dated to around 7.5 billion years old.
The grains are suspected to be pre-solar grains, which means they arose during the death of a distant star.
The meteorite the grains were pulled from, the Murchison meteorite, is one of the most well-studied meteorites in the world.
Earth formed alongside the rest of the solar system roughly 4.6 billion years ago. The oldest rocks we’ve found to date are about 4.03 billion years old, but the oldest earth minerals ever discovered were actually found in lunar samples and date to about 4.1 billion years.
Now, scientists believe they’ve discovered the oldest material ever found on Earth: microscopic specs of dust pulled from meteorite dated at 7.5 billion years old, according to research published January 13 in the journal Proceedings of the National Academy of Sciences.
An international team of researchers, led by astronomer Philipp Heck of the University of Chicago and the Field Museum, believes the minuscule dust grains may be leftovers from a stellar explosion billions of years ago. As that dust flies through space, it gets scooped up by passing meteorites and comets.
The meteorite in which the grains were found is one of the most well-studied meteorites on Earth. The 220-pound Murchison meteorite plummeted to Victoria, Australia on September 28, 1969. (There were witnesses, too—a rare treat for studied meteorites.) It’s a type of meteorite called a carbonaceous chondrite, and it's one of the most primitive known to science.
The scientists took a small sample of the extraterrestrial rock and crushed it into a fine powder for analysis. They then turned it into a paste, which, according to the BBC, smells like rotten peanut butter. The grains were then dissolved out and dated using an isotope of the element neon, Ne-21.
Ten percent of the grains are older than 5.5 billion years, Heck told the BBC. Most, around 60 percent, dated to between 4.6 and 4.9 billion years old. The oldest, however, were a whopping 7.5 billion years old. Curiously, evidence suggests that the dust grains actually traveled in clumps, like granola.
This new discovery will help scientists like Heck better understand patterns of star growth in the solar system. For example, do they form at a steady rate or are there heightened periods of activity? (This latest discovery suggests the latter.)
Heck suspects there are probably other grains just like this one, just waiting to be discovered.
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