DNA and RNA Came from Space
- Researchers find nucleobases in meteorite fragment
By: Gabriel Gache, Science News Editor
http://news.softpedia.com/news/DNA-and-RNA-Came-from-Space-88016.shtml
For some reason or another, all of us like to believe that Earth is special - after all, our planet is the only one able to sustain life that we know of. Indeed, Earth is special in its own way, but life would not have been possible without the significant contribution of material coming form space. In fact, a new study shows that the compounds making up DNA and RNA actually originated in space, not on Earth as previously thought, and were brought here by meteorite fragments and other similar objects.
"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," said the leader of the study, Zita Martins of the Department of Earth Science and Engineering at Imperial College
London.
In 1969, a meteorite fragment, known today as the Murchison meteorite, crashed in the Australian outback. A thorough analysis, following its discovery, showed that it contained uracil and xanthine molecules (nucleobases), which are building blocks for genetic materials made up of a heavy carbon isotope. On Earth, such molecules contain only light carbon isotopes.
However, these two molecules are just a few of many others found in the respective fragment. "There are about 70 different amino acids in the Murchison meteorite. About six or so are the same kinds of amino acids associated with life on Earth," said David Deamer from the University of California.
The uracil molecule is one of the four bases for the RNA molecule, therefore it is invaluable to life. Deamer points out that, although these molecules have been proven to originate in space, they could have been developed on Earth just as well. Nevertheless, the proportion of molecules originating only in space or only on Earth is currently unknown.
"We don't know the answer yet. Most people would say that both contributed to the organic compounds available on Earth, but we don't know with certainty how much of one compared to the other," said Deamer.
Between 3.8 and 4.5 billion years ago, when primitive life first appeared, the Earth and Mars could have been literally bombarded with meteorites similar to the Murchison, thus studying the impact they would have had on different planets could reveal how life evolved in the solar system.
"Because meteorites represent leftover materials from the formation of the solar system, the key components for life - including nucleobases - could be widespread in the cosmos. 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," said Mark Sephton, professor of Earth science and engineering at Imperial College London and co-author of the study
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