DNA: It came from outer space?
The Murchison meteorite contains molecules that form the very building blocks of DNA and RNA. This discovery was made by a team of scientists from the UK, the Netherlands and the USA. The molecules found include uracil and xanthine, which are known as nucleobases and are precursors to the molecules that make up DNA and RNA. The results have been published in a paper in the journal Earth and Planetary Science Letters. The meteorite crashed in late September 1969 just outside the town of Murchison in Victoria, Australia. Scientists have been analysing the Murchison meteorite ever since it landed, making it the most studied meteorite in its category. Dr Zita Martins, from the Department of Earth Science and Engineering at Imperial College London, is lead author of the article. According to her, their research may provide another piece of evidence explaining the evolution of early life. 'We believe early life may have adopted nucleobases from meteoritic fragments for use in genetic coding which enabled them to pass on their successful features to subsequent generations,' she comments. Over the last two centuries, meteors have been collected from approximately 35 observed falls of what are known as 'carbonaceous chondrites'. Like the Murchison meteorite, these meteors have high levels of water and organic compounds. They also contain materials coalesced from dense molecular clouds during or prior to the formation of the solar system. They are of special interest to researchers because, like life on Earth, they contain organic or carbon-based compounds. The analysis of the Murchison meteorite indicates that the nucleobases contain a heavy form of carbon which could only have been formed in space. Materials formed on Earth consist of a lighter variety of carbon. The meteor was also rigorously tested to determine whether the molecules came from the solar system or were a result of contamination when the meteorite landed on Earth. Co-author of the study, Professor Mark Sephton, also from the Department of Earth Science and Engineering at Imperial College, believes this research is an important step in understanding how early life might have evolved. 'Because meteorites represent left over materials from the formation of the solar system, the key components for life -- including nucleobases -- could be widespread in the cosmos,' he explains. 'As more and more of life's raw materials are discovered in objects from space, the possibility of life springing forth wherever the right chemistry is present becomes more likely.'
Countries
Netherlands, United Kingdom, United States