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.
Photo: AFP
照片：法新社
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.
(Translated by Paul Cooper, Taipei Times)
科學家對一九六九年墜落在澳洲的一顆隕石進行分析，發現其中含有許多在太陽系形成前就已存在的星塵，最久遠者更可追溯到約七十五億年前，是迄今在地球上能找到的最古老物質。研究結果刊登於美國國家科學院院刊。
這顆被分析的隕石是在一九六九年九月二十八日墜落於澳洲維多利亞省默奇森附近。來自美國及瑞士的研究團隊將隕石磨碎後溶於酸中，只留下其中的星塵，並測量這些星塵暴露於宇宙射線下的時間，以確定其年齡。
這項研究的第一作者赫克指出，結果發現隕石中有百分之九十的星塵可追溯到四十六億至五十五億年前，其餘一成則有逾五十五億年的歷史，其中最古老者約有七十五億年歷史。作為對比，太陽系大約是在四十六億年前開始形成。
雖然成功發現迄今地球上最古老的物質，但赫克相信，默奇森隕石及其他隕石中還有更多比太陽系更古老的物質，只是還沒有被科學家發現。
（自由時報）
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