This article was published in the daily newspaper Le Parisien, France, June 14, 2008.
We all are a little extraterrestrial: elements essential to the emergence of life on Earth came from space, affirms an international team of researchers who analyzed the structure of a meteorite fallen on Australia.
The European and American scientists proved that the nitrogenized bases (or nucleic bases) of the meteorites, present in the DNA of living cells, did come from space and did not contaminate it after their fall on Earth.
"The analysis shows that the nitrogenized bases contain a heavy carbon variety which can only be formed in space. The materials formed on Earth contain a lighter variety of carbon", the Imperial College of London, whose two researchers took part in the study, affirmed in an official statement.
The contribution of the meteorites to the emergence of the life on Earth, a long time considered as a possibility, becomes much more probable.
By measuring the contents of carbon isotopes in two molecules found on the meteorite of Murchison, fallen on Australia in 1969, the scientists who publish their Sunday results in the British review Earth and Planetary Science Letters noted that it was a type of carbon different from that from the terrestrial rocks.
This discovery consolidates the theory according to which "the raw materials necessary to the life which were brought on the primitive Earth (between 4,5 and 3,8 billion years) are of exogenic origin", declared Zita Martins, co-author of the article, to the AFP.
She adds that "the atmospheric conditions on the primitive Earth were not ideal for the synthesis of the nitrogenized bases" thus the emergence of the life, which however started to appear at that time.
And at the time where the solar system was still in the course of formation some 4 billion years ago, the planets were sumbitted to a ceaseless bombardment of meteorites.
This is why "we think that the first forms of life took nitrogenized bases found on fragments of meteorites to use them in genetic coding", thus allowing the transmission of their characteristics for the future generations, explains Mrs. Martins.
The mystery of life is not entirely solved however. "Nobody knows exactly how, from the existence on Earth of these bricks of construction (necessary to the appearance of the life), life it-self appeared", this astrobiology expert admits.
For his colleague Sephton Mark, also of the Imperial College, the confirmation of the extraterrestrial origin of these molecules in the meteorites could have implications for the life elsewhere than on Earth.
"Key elements of life - mong those nucleic bases - could be widespread in the universe. As raw materials for life are discovered in space, the possibility of the emergence of life where the conditions are favourable becomes more probable", he estimates.
Note: the abstract of the paper can be read here (External link).
