It’s been known for decades that complex molecules can be formed in space, now evidence have been found that some building blocks of DNA can be formed in meteorites.

One of the problems in the analysis of meteorites is to establish that the organic molecules actually arrived on Earth inside them and aren’t the result of a subsequent contamination. A new research shows evidence of extraterrestrial origin of these molecules.

Scientists at the Goddard Astrobiology Analytical Laboratory in the past had already found aminoacids in the comet Wild 2 during the Stardust mission. Now however at NASA Goddard Space Flight Center a new research have been carried out on twelve carbon-rich meteorites, nine of which have been found in Antarctica.

The result was the discovery of the presence of adenine and guanine, two nucleobases which are DNA components. They also found Xanthine, another purine base, and hypoxanthine, a purine derivative, used in some biological processes.

In two of the meteorites they found nucleobases analogs such as 2,6-diaminopurine and 6,8-diaminopurine, hardly ever used in biological processes. This excludes almost entirely terrestrial contamination because it’s unlikely that molecules which are rare on Earth might contaminate meteorites. Instead you can expect that in the extraterrestrial spontaneous formation of organic molecules there are also some which don’t exist or are rare on Earth.

The team of scientists also analyzed a sample of Antarctic ice using the same methods used on meteorites, most of which were found in that continent. The amount of nucleobases found is much lower: concentration in the ice is a few parts per trillion but in meteorites they’re found in several parts per billion. A more significant result is that in the ice they found no traces of analogs such as 2,6-diaminopurine and 6,8-diaminopurine.

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One of the meteorites was found in Australia so a soil sample of the area has been analyzed in the same way. Again they found no traces of nucleobases analogs.

Further evidence of the fact that these molecules were formed in meteorites is the fact that in the laboratory the same group of nucleobases and nucleobases analogs has been created through non-biological chemical reactions using simple molecules such as hydrogen cyanide, ammonia and water. Thus there’s a mechanism that leads to the formation of such complex molecules in the bodies the analyzed meteorites arrive from.

This research expands our knowledge about the birth of life on Earth. We’re actually still unable to say whether the building blocks that led to the birth of DNA all formed on Earth, all in space or in part on Earth and in part in space. The important thing is that bit by bit we’re understanding the various mechanisms that led to the formation of DNA. This will also allow us to better understand in what conditions life can arise outside the Earth.