每日英語跟讀 Ep.779: 7.5 billion-year-old meteorite contains oldest material ever found on Earth
Scientists analyzing a meteorite that fell down onto an Australian village in 1969 have discovered that the rock contained many particles of stardust that existed before our solar system was formed, dating them to around 7.5 billion years ago, making them the oldest material ever found on the Earth. The study findings have been published in the American scientific journal Proceedings of the National Academy of Sciences.
The meteorite that was analyzed fell to the Earth in the area around the village of Murchison in Victoria, Australia on Sept. 28, 1969. A team of scientists from the US and Switzerland placed ground particles of the meteorite in acid to remove all the material, leaving only the stardust. They then measured the length of time that this stardust would have been exposed to cosmic rays, in order to determine its age.
According to Philipp Heck, the primary author of the study, they determined that 90 percent of the stardust in the meteorite was dated to between 4.6 billion and 5.5 billion years ago, with the remaining 10 percent being over 5.5 billion years old, of which the oldest was around 7.5 billion years old. By comparison, the solar system started to form around 4.6 billion years ago.
Although this stardust is the oldest material discovered thus far on Earth, Heck believes that there is even more material older than the solar system in the Murchison meteorite and in other meteorites, it’s just that they have yet to be discovered by scientists.
Source article: http://www.taipeitimes.com/News/lang/archives/2020/01/20/2003729528