Meteorites contain all the 'letters' that make up the alphabet of life, that is, all five nitrogenous bases that make up DNA and Rna: not only adenine, guanine and uracil, as had been previously discovered, but also cytosine and thymine.
These last two bases, so far escaped from analysis because they are very delicate and easily degradable, have been identified thanks to a new extraction technique by an international team of experts led by Yasuhiro Oba of the University of Hokkaido in Japan, which was also attended by the NASA.
The study is published in Nature Communications.
"We now have evidence that the full set of nitrogenous bases underlying life today could have been available on Earth when life emerged," says Danny Glavin, co-author of the study at NASA's Goddard Space Flight Center.
This is not yet the smoking gun that proves that life on Earth appeared thanks to a spacecraft, but it is an important clue that offers researchers new tools with which to do further study.
Previous experiments had succeeded in isolating three of the five nitrogenous bases from meteorite samples by making an extract with a technique similar to that of preparing hot tea: in practice, the meteorite grains were immersed in a hot solution containing formic acid, a molecule highly reactive which may have degraded cytosine and thymine.
To avoid this, the researchers thought of making a kind of cold brew, using cold water to extract the bases.
The technique was applied to the samples of three carbonaceous meteorites (one that fell in Australia in 1969, one that ended up in Kentucky in 1950 and one that fell in British Columbia in 2000) and proved successful, so much so that it could also be used in the analysis of future asteroid samples such as those of Bennu,
