Life on Earth could have started with comet impact, scientists prove

They theorised that around four billion years ago our planet was bombarded with rocks and balls of ice carrying molecules which, under the huge pressure of impact, could split into the elements needed to form DNA.

And now, for the first time, they have proven it in the lab.

Scientists have shown that formamide molecules – which have been found in comets - can break down into some of the nucleobases that make up DNA when under great heat and pressure.

A team at the Central European Institute of Technology in the Czech Republic used a high powered laser to reproduce the forces at work when a comet hits the surface of Earth such as a sudden extreme rise in temperature, shock waves and radiation.

They were able to break up formamide into three of the nucleobases which make up our DNA, adenine, guanine, cytosine. 

Only thymine was missing. However all the nucleobases for RNA were present.

Our DNA comprises of four nucleobases which join into pairs to form rungs on the ladder of the double-helix.

The scientists say the experiment solves a ‘central problem in origin-of-life research’ and shows that the impact alone of a meteorite or comet can transform a simple chemical into the letters of our genetic alphabet.

Although it's been known for years that scientists can coax formamide to recombine into DNA nucleobases, it is the first time that they have shown it can happen spontaneously during a high-energy event.

"The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules,” said lead author Dr Svatopluk Civis.

"Our findings demonstrate that extraterrestrial impacts, which were one order of magnitude more abundant during the LHB period than before and after, could not only destroy the existing ancient life forms, but could also contribute to the creation of biogenic molecules.”

"The first bio- signatures of life are dated to roughly coincide with the LHB or near the end of it.

"In conclusion, all these findings suggest that the emergence of terrestrial life is not the result of an accident but a direct consequence of the conditions on the primordial Earth and its surroundings.”

The report was published in the journal the Proceedings of the National Academy of Sciences.

(telegraph.co.uk)