The question of the origin of life may soon be answered and the answer may be that it came from elsewhere. Shreds of DNA building material have been found on meteorites pointing to a possibility of Earth being seeded with life from elsewhere.
Scientists, from different institutes, found that not only were traces of compounds like ammonia and cyanide present, which could build complex organic molecules, even nucleobases (a group of nitrogen-rich organic compounds that are needed to build nucleotides, which can make RNA or DNA – the basis of all terrestrial life) were seen. This is not the first time nucleobases were being seen in meteorites, however. As Jim Cleaves, a chemist at the Carnegie Institute of Washington said to Space.com
People have been finding nucleobases in meteorites for about 50 years now, and have been trying to figure out if they are of biological origin or not.
The hardest part of the study was confirming that the meteorites were not contaminated with organic material lying around. The study found a huge number of different nucleobases in organic-rich meteorites called carbonaceous chondrites, out of which three were extremely rare on Earth. This gives credence to the idea that life may have been planted from elsewhere.
The hypothesis that states that life was seeded on Earth from extra-terrestrial sources is called Panspermia’. It has had its share of strong supporters and equally vociferous deniers, but this does seem a point in its favour. Experiments in chemistry labs have repeatedly shown that building complex organic compounds, like nucleobases, from compounds such as cyanide and ammonia, in the presence of water, isn’t too difficult. This was first shown by the Urey-Miller experiment in 1952 (the same year as the discovery of the DNA double helix by Watson and Crick). They could produce amino acids, the building blocks of protein, by passing electricity through a flask containing gaseous ammonia, hydrogen sulphide, carbon dioxide, cyanide and sulphur dioxide, along with water. It is surmised that the step from amino acids to actual proteins may not be very tough.
These findings say that it might have been even easier. Specifically, different molecules belonging to the citric acid cycle have been found. The citric acid cycle is one of the oldest biological cycles and plays a crucial role in respiration of all living forms.
The studies were published in the Proceedings of the National Academy of Sciences.