Meteorites contain a large variety of nucleobases, an essential building block of DNA.
Credit: NASA's Goddard Space Flight Centre/Chris Smith
WASHINGTON: New evidence has strengthened the case for organic-rich meteorites bringing the crucial building blocks of DNA to the early Earth.
It's a debate that has spanned over 50 years - were the materials needed to form early life delivered to Earth via an extra-terrestrial source, or was that extra-terrestrial source contaminated upon arrival?
In the current issue of the Proceedings of the National Academy of Sciences, new research indicates that nucleobases, which are essential in forming DNA and RNA, were transported by carbonaceous chondrites, a type of meteorite rich with organic compounds that give rise to life on Earth.
"People have been discovering components of DNA in meteorites since the 1960s, but researchers were unsure whether they were really created in space or if instead they came from contamination by terrestrial life," said Mike Callahan, astrobiologist and lead author of the study at NASA's Goddard Space Flight Centre in Greenbelt.
Evidence supports extra-terrestrial origin
Advanced spectroscopy techniques were used to analyse 12 types of carbonaceous chondrites and one ureilite, a rare meteorite with a unique chemical composition. It was the first time all but two of these meteorites had been tested for nucleobases.
Two of the carbonaceous chondrites contained a diverse array of nucleobases and compounds that are similar, known as nucleobase analogs. They included purine, 2,6-diaminopurine and 6,8-diaminopurine.
The three nucleobase analogs found are "rare or absent in terrestrial biology", said Jim Cleaves, one of the authors of the study from the Carnegie Institute of Washington's Geophysical Laboratory. "Finding nucleobase compounds not typically found in Earth's biochemistry strongly supports an extra-terrestrial origin," he said.
Native building blocks
During the study, the team tested their conclusion with experiments to reproduce nucleobases and analogs using chemical reactions of ammonia and cyanide, which are commonly found in space. The results were very similar to those found in the carbonaceous chondrites.
Amino acids are used to make proteins which are the "workhorse molecules for life", said the study. Proteins are used for structures such as hair and enzymes, which are the catalysts that speed up or regulate chemical reactions.
"This is a very exciting study on the range of organic molecules that are synthesised extra-terrestrially and delivered to the Earth," said Lewis Dartnell, astrobiologist at the University College London, UK, who was not involved in the study. "Nucleobases have been found before in meteorites, but this study shows just how diverse the nucleobases from space are, and how many different meteorites they are found in. If organic molecules are synthesised in space, they were also likely to have been created in abundance here on Earth too, so most likely the first life was mainly composed of native building blocks, but perhaps incorporating a small proportion of extra-terrestrial components too."
a far-fetched conclusion?
I cannot believe that a science writer of your calibre can make such a far-fetched conclusion as this:
"The findings suggest that life was partly created in space, essentially meaning that strands of DNA are in fact alien in origin."
How can you conclude from these data that "strands of DNA are alien in origin"? This is not what the research tells us! It simply shows that some bases may have come from space - nothing more, nothing less. This conclusion is totally non-scientific.
It says "the findings
It says "the findings suggest..." Thats not the writers comment, nor is it a conclusion. Its relaying the information which was presented in the study. Thats the journalists job.
DNA has an alien origin
This information does not confirm the hypothesis that life came from space. There are at least two equally possible alternatives:
A) If DNA’s elements can appear in meteorites and comets, why not also on planets?;
2) Life did not come from space (this is the theory of panspermia), but from the evolution of the whole space as a system. There was no "origin" of life, living beings are biological systems and only product of the evolution of astronomical systems, to which the Earth belongs (this is the Matrix / DNA Theory).
The press has a responsibility to avoid being the spokesman of ideologies that tomorrow may be in the school curriculum forming the minds of young people who, when they are indoctrinated with wrong views of the world lose their own initiative to think and seek the truth themselves.
This is an opportunity for “thinkers outside the box” researchers. The belief that life came from space is growing because they can not make the Urey’s amino acids making the next step that should be to form proteins and RNA. So, they did give up this way and are seeking another solutions to the origins of life and knowledge of important natural mechanisms. But in the Amazon we have discovered the possibility of the existence of the Matrix / DNA and would be this formula that is missing for the amino acids produced in the Earth. (See the formula on the website of "The Matrix Universal Vital Natural Systems and Cycles").
Implied extraterrestrial origin
Just for the record, finding nucleobase compounds is far from proof their is life elsewhere. We will need much more evidence!
Aliens and DNA
Interesting, but lets first establish that organic-rich life actually does exist out there before we presuppose that 'organic-rich' meteorites brought it here. It's hard to resist putting the cart before the horse, as we all know.
To the first comment...
The line said "the findings suggest..."
Well thats not the opinion of the writer, nor is it a conclusion, its relaying what the original study has presented. Thats what the journalists do.