Scientists have discovered exciting new evidence that life was brought to the Earth from space. They found the highest ever concentration of life’s essential ingredients in two ancient meteorites that crashed to the ground long ago.
The space rocks were discovered lying in the Antarctic by explorers in the 1990s after centuries preserved by nature’s own deep freeze.
A study led by Dr Zita Martins, of Imperial College London, shows that they hold high levels of amino acids which form the basis of proteins and enzymes – the building blocks of all biological life.
The carbon-rich meteorities – termed chondrites – are believed to be fragments of asteroids that formed shortly after the birth of the solar system. Earlier research found the building blocks of life in carbon bubbles within a meteorite that fell over Canada in 2000.
Dr Martins and international colleagues believe the Antarctic meteorites provide clear evidence that the early solar system was richer in life’s raw materials than previously thought. They say these materials may have helped to kick-start life on this planet.
Dr Zita Martins, from Imperial College’s Department of Earth Science and Engineering, said: “We know that approximately 3.8 to 4.5 billion years ago the Earth underwent heavy bombardment from meteorites which brought molecules to our planet, just before life emerged on Earth.
“However, there is a gap in knowledge about how life came into being. Our work has shown that it may have been meteoritic amino acids and other biologically useful compounds that spurred life into existence.”
By analysing the content of the two meteorites, Dr Martins’ team were able to determine that, unlike Earth based amino acids which prefer a lighter variety of carbon, their samples were made from a heavier carbon which could only have been formed in space.
Dr Martins says her work provides new insights into the chemistry of the early solar system and the resources available for early life.
“Our increasing understanding of the materials available for the first living systems in the solar system suggests that we are all products of cosmic chemistry,” said Dr Martins.
Dr Martins conducted her research with colleagues at the Leiden University, Netherlands, in association with the Carnegie Institution of Washington and Nasa’s Jet Propulsion Laboratory in California.
Their work on the two meteorites – dubbed EET92042 and GRA95229 – is published online in the journal Meteoritics and Planetary Science.
The Antarctic has proved a fertile hunting ground for meteorites because they can lie undisturbed on the snow and ice for many thousands of years.
One meteorite found there from Mars hit the headlines in 1996 when Nasa announced they had found signs of fossilised martian bacteria inside it. It is now believed that the “fossils” are really terrestrial contamination but scientists say there are still signs of life’s building blocks in that meteorite too.
Traces of martian organisms are also said to have been detected in a meteorite that fell over Egypt in 1911 and which has been kept in the Natural History Museum in London.
Picture: An artist’s impression of asteroids drifting in space. NASA/JPL-Caltech