Components of DNA have been found in several meteorites ever since the 1960’s, but the question that continually lingered was whether these components were actually made in space, or rather the result of terrestrial contamination. Now, NASA-funded researchers present three lines of evidence that should support the notion that these DNA building blocks were made in space (see figure 1).

Figure 1: DNA blocks made in space?

(Source: NASA)

So, can the building blocks of life be made inside meteorites?

To investigate this question, the research team ground up samples of twelve meteorites, and after some further processing, these samples were analyzed with a liquid chromatograph and a mass spectrometer, allowing the researchers to determine the chemical structure of the compounds in the samples. They found a variety of molecules, including DNA building blocks adenine and guanine, but also hypoxanthine and xanthine, which are not found in DNA, but do play a role in other biological processes. Besides these, trace amounts of three other molecules, related to nucleobases, were found. Purine, 2,6-diaminopurine and 6,8-diaminopurine are nucleobase analogs and have the same basic structure as nucleobases, but with a structure added or removed (see figure 2).

Figure 2: Meteorite and molecules found in it.

(Source: NASA)

These analogs provide the first line of evidence for the claim that life’s building blocks can be made in space, as they are not used in biology. This makes terrestrial contamination less likely. If, however, these meteorites act as 'chemical factories', spewing out prebiotic materials, such analogs could be expected.

The second line of support is that the researchers investigated soil samples from the sites where the meteorites were collected. They found that the two nucleobases, hypoxanthine and xanthine were found in much lower concentrations in these soil samples, and, more importantly, that none of the analogs were present.

Lastly, the research team found that the molecules found in the meteorites could all be produced in non-biological reactions. They were able to create an identical suite of molecules using hydrogen cyanide, ammonia and water, providing a plausible mechanism for their synthesis in meteorites.

There even seems to be a ‘goldilocks’ class of meteorites, the so-called CM2 meteorites, where the conditions are perfect for the synthesis of these prebiotic molecules.

Following video summarizes the research.

This seems to provide support to the notion that the earth was ‘seeded’ with the molecules necessary for the development of life through meteorites. Maybe we’re all aliens…

Reference

NASA. News Topics. NASA Researchers: DNA Building Blocks Can Be Made In Space. Published August 8th, 2011.