Tuesday, August 23, 2011
Life Originating from Space Rocks? Maybe.
For well over half a century, astro-biologists, astronomers and others have debated whether the theory of Panspermia might be valid, and if so, how would it manifest. The basic idea is that the "spores of life" would be carried to Earth, most likely on meteorites, and then the building blocks - given the right chemical reactions (say in the primitive reducing atmosphere) would have given rise to a prokaryotic cell.
Now, new findings may shed more light on this. A more recent analysis of a dozen meteorites found in Antarctica and elsewhere (e.g. Australia)conveys the strongest positive answer yet. In addition, the findings disclose the possibility that the components of extra-terrestrial DNA could have spontaneously formed in space.
As a brief refresher, meteorites (such as the Murchison meteorite shown, which impacted some 42 years ago in Murchison, Victoria, Australia) are space rocks that have made it through the Earth's atmospere and struck the ground. In actual fact, they are likely the remnant portions of much larger space rocks, most of which burned up on entry. The point is, it's conceivable that early meteorite bombardment might have seeded the Earth with the building blocks of life. This, as opposed to life originating autonomously on the Earth.
According to thr authors of a just-released report appearing in The Proceedings of the National Academy of Sciences:
"Meteorites may have served as a molecular kit providing essential ingredients for the origin of life on Earth and possibly elsewhere"
In effect, a qualified validation of Panspermia.
The key point is that all terrestrial plants and animals depend on DNA to store information. At the center of the ladder-like DNA molecule (see diagram) are ring-like structures called nucleotides. It is these tiny structures that scientists at NASA and the Carnegie Institute found in 11 of the 12 meterorites they examined.
Two of the samples, from the Murchison meteorite and one designated 'Loneolf Nunataks 94102', contained an array of nucleo-bases including those also found in DNA.
But another surprise was also found: each of the two samples mentioned also included exotic, or "extra-terrestrial" bases never seen before. This, according to Michael Callahan the NASA astro-geologist who analyzed the space rocks. Meanwhile, analysis of dirt and rocks in the vicinity of the meteorites showed no evidence of the same exotic nucleo-bases, hence contamination was unlikely. And in any case, the exotic nucleo-bases have never before been seen on Earth.
While amino acids have been found in other meteorites, this is the first time these DNA nucleo-bases have been uncovered. According to one Carnegie investigator:
"These molecules are at the core of life's blueprints. It's possible that the presence of these molecules in meteorites made us what we are today"
Indeed, and possibly made extra-terrestrials (hitherto undiscovered) what they are today too. Let us hope that if found, they are more like us in the best ways, and not the worst!