Natural Science Forum / Biology / Evolution / June 2008

Scientists confirm that parts of earliest genetic material may have come
from the stars

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."

Paper: "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:
http://dx.doi.org/10.1016/j.epsl.2008.03.026

Source: Imperial College London
http://www.physorg.com/news132577096.html

Posted by
Robert Karl Stonjek