Meteorite Grains Are the Oldest Known Solid Material on Earth
by Jay Bennett, Smithsonianmag.com
A little more than 50 years ago, on September 28, 1969, a meteorite crashed near the rural village of Murchison in Victoria, Australia. Witnesses saw a fireball streak through the sky and break into three pieces just before 11 a.m. local time, followed by an audible tremor in the area. Locals came upon several fragments of the meteorite, the largest of which, with a mass of 680 grams, crashed through a roof and landed in a pile of hay. Altogether, some 100 kilograms of the Murchison meteorite were recovered and sent to scientific institutions around the world.
“The Murchison meteorite is a wonderful resource for the scientific community,” says Philipp Heck, a curator of meteorites at the Field Museum in Chicago, which houses a large portion of the extraterrestrial object. “It contains some of the oldest condensates in the solar system and also presolar materials.”
Some of those presolar materials—microscopic grains that formed before the sun, measuring about 2 to 30 micrometers across—have been dated at 4.6 to 4.9 billion years old. And one of the grains analyzed in a study published today in the Proceedings of the National Academy of Sciences is estimated to be roughly 7 billion years old, making it the oldest known material on Earth.