Scientists have confirmed for the first time that an important component of early genetic material which has been found in meteorite fragments is extraterrestrial in origin, in a paper published on 15 June 2008.
The finding suggests that parts of the raw materials to make the first molecules of DNA and RNA may have come from the stars.
The scientists, from Europe and the USA, say that their research, published in the journal Earth and Planetary Science Letters, provides evidence that life's raw materials came from sources beyond the Earth.
The materials they have found include the molecules uracil and xanthine, which are precursors to the molecules that make up DNA and RNA, and are known as nucleobases.
The team discovered the molecules in rock fragments of the Murchison meteorite, which crashed in Australia in 1969.
They tested the meteorite material to determine whether the molecules came from the solar system or were a result of contamination when the meteorite landed on Earth.
The analysis shows 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.
Lead author Dr Zita Martins, of the Department of Earth Science and Engineering at Imperial College London, says that the research may provide another piece of evidence explaining the evolution of early life. She says:
"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."
Between 3.8 to 4.5 billion years ago large numbers of rocks similar to the Murchison meteorite rained down on Earth at the time when primitive life was forming. The heavy bombardment would have dropped large amounts of meteorite material to the surface on planets like Earth and Mars.
Co-author Professor Mark Sephton, also of Imperial's Department of Earth Science and Engineering, believes this research is an important step in understanding how early life might have evolved. He added:
"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. 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."
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Dr Zita Martins
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Imperial College London
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Notes to editors:
1. "Extraterrestrial nucleobases in the Murchison meteorite", Earth and Planetary Science Letters, Sunday 15 June 2008 (Print publication)
A full copy of the research can be downloaded at:
Zita Martins (1,2), Oliver Botta (3,4,5), Marilyn L. Fogel (6), Mark A. Sephton (2), Daniel P. Glavin (3), Jonathan S. Watson (7), Jason P. Dworkin (3), Alan W. Schwartz (8), Pascale Ehrenfreund (1,3)
(1) Astrobiology Laboratory, Leiden Institute of Chemistry, 2300 RA Leiden, The Netherlands
(2) Department of Earth Science and Engineering, Imperial College, London, SW7 2AZ, UK
(3) NASA Goddard Space Flight Center, Code 699, Greenbelt, MD 20771, USA
(4) Goddard Earth Sciences and Technology Center, University of Maryland Baltimore, County, Baltimore, MD 21228, USA
(5) International Space Science Institute, Hallerstrasse 6, 3012 Bern, Switzerland
(6) GL, Carnegie Institution of Washington, Washington, DC 20015, USA
(7) Planetary and Space Sciences Research Institute, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
(8) Radboud University Nijmegen, 6525 ED, Nijmegen,The Netherlands
2. About Imperial College London
Imperial College London - rated the world's fifth best university in the 2007 Times Higher Education Supplement University Rankings - is a science-based institution with a reputation for excellence in teaching and research that attracts 12,000 students and 6,000 staff of the highest international quality. Innovative research at the College explores the interface between science, medicine, engineering and business, delivering practical solutions that improve quality of life and the environment - underpinned by a dynamic enterprise culture. Website: www.imperial.ac.uk