If Life Is Out There, We're Not Related
Paul Falkowski, a Rutgers professor of biochemistry and biophysics, believes he has proof that life on earth was not seeded from a comet; “The two fundamental questions in science are: where did we come from, and are we along? Almost certainly, any life in our solar system evolved uniquely in this solar system.", Falkowksi said.
Samples of microbes that had been frozen in the Antarctic ice for millions of years had DNA that suffered extensive deterioration. Cosmic radiation was responsible for the deteriorated state of the microbes DNA. The potential for microbes to survive on or in comets as they travel through deep space is dismal. “It’s almost an impossibility for comets to seed other planets with life after they’ve been in space for millions of years”, he stated.
During its travel the comet would be bombarded by cosmic radiation. Any genetic or organic material would become so corrupted and damaged by this radiation that hopes for a successful seeding would be wiped out. The organic material would be destroyed.
These findings may be significant in dispelling the notion of panspermia; the belief that life on earth was seeded from an outside source. The theory involves the possibility of microbes traveling on comets or meteors, the comets striking the earth and the organic contents inhabiting their new home.
Astronomer Kevin Conod believes that there still may exist the possibility for panspermia. Conod state, “Radiation might be a problem for microbes, but not for very basic organic material”. However, the idea that radiation would not have an adverse effect on basic organic molecules is not well supported. Exposed to radiation, even these basic constituents of life would suffer deterioration. The radiation would initiate a radical reaction; the bumping of one electron out of its orbit or the homolytic cleavage of a covalent bond would create a free radical. The propagation step would then follow; these highly reactive free radicals would bond with some other molecule causing it to lose one of its original constituents in the form of another free radical. This process would continue until termination, the uniting of two free radicals. Because the concentration of free radicals in relation to non-free radical organic molecules is always minute, the propagation step can and will carry on for some time.
Regardless of whether microbes or basic organic molecules are the ones catching a ride on the comet, neither would be exempt from the deteriorative effects of cosmic radiation. Unless it can be shown that the interior of a comet can provide a suitable bivouac protected from cosmic radiation, it would appear that panspermia is conceptually flawed as a theory for how life arrived and subsequently developed on earth. Link