Editor's Note: This story was updated at 3:45 p.m. EDT.
We may all be aliens, it seems.
Some of the building blocks of life on Earth came fromspace, according to a new study of molecules in meteorite fragments.
The study confirmed that some of the raw material for DNAand RNA found in a meteorite did not contaminate the rock after it landed onEarth, but actually originated in space.
The materials in question are the molecules uracil andxanthine, which are precursors to the compounds that make up DNA and RNA, andare known as nucleobases.
"We believe early life may have adopted nucleobasesfrom meteoriticfragments for use in genetic coding which enabled them to pass on theirsuccessful features to subsequent generations," said the study's lead author,Zita Martins, a researcher in the Department of Earth Science and Engineeringat Imperial College London.
Martins and her colleagues detailed their findings in theJune 15 issue of the journal Earth and Planetary Science Letters.
The team discovered the molecules in rockfragments of the Murchison meteorite, which crashed in Australia in 1969.The scientists analyzed the genetic building blocks and found that they containa heavy form of carbon which could only have been formed in space. Materialsformed on Earth are made of a lighter type of carbon.
The two molecules in this study are only a few of theorganic molecules that have been detected in the famous Murchison meteorite,said David Deamer, a chemist at the University of California, Santa Cruz.
"There are about 70 different amino acids in the Murchisonmeteorite," Deamer told SPACE.com. "About six or so are thesame kinds of amino acids associated with life on Earth."
Uracil is one of the four base molecules of RNA, so is vitalfor life.
Just because the molecules found on this meteorite and otherscame from space, doesn't mean the same compounds weren't also independentlysynthesized on Earth, Deamer pointed out. Scientists are unsure how many of thebuilding blocks of life on Earth originated on this planet, and how many camefrom beyond.
"We don?t know the answer yet," he said. "Mostpeople 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."
Many space rocks similar to the Murchison meteorite raineddown on Earth between 3.8 and 4.5 billion years ago, when primitive life wasforming. The heavy bombardment would have dropped large amounts of meteoritematerial to the surface on planets such as Earth and Mars.
Martins and her colleagues say their discovery may help shedlight on how life first evolved in our solar system.
"Because meteorites represent leftover materials fromthe formation of the solar system, the key components for life - includingnucleobases - could be widespread in the cosmos," said co-author MarkSephton, a professor of Earth science and engineering at Imperial CollegeLondon. "As more and more of life's raw materials are discovered inobjects from space, the possibility of life springing forth wherever the rightchemistry is present becomes more likely."
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