E.T. phone home
NASA scientists found both terrestrial and extraterrestrial nucleotides on meteors in the Antarctic and Australia. The experiments were performed with minimal risk of earthly contaminants. Perhaps, per the immortal words of Joni Mitchell, “we are star dust” after all.
Maybe biologists and chemists have underestimated the likelihood elsewhere in the universe of the spontaneous emergence of the reproducible molecular order that is responsible for life as we know it?
Or conversely, might astronomers overestimate the probability of life on other planets, given their innate appreciation of the enormity of the universe, relative to their appreciation of the molecular complexity associated with all the workings of robust, reproducing cells?
The nice thing about science, is that new results can shed new light on these age old questions over time. We can get a better sense of what is likely based on real data.
In a remarkable PNAS article titled “Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases” Callahan & coworkers state:
“The presence of extraterrestrial purines in meteorites has
far-reaching implications. The first cellular systems on the early
Earth were presumably assembled from three components: nucleic acids, proteins, and cell membranes (31). Potential molecular subunits for constructing all of these macromolecular species (e.g., amino acids, amphiphilic compounds, and from this study— a variety of purine nucleobases) have been identified in meteorites and appear to be indigenous. Thus, meteorites may have served as a molecular kit providing essential ingredients for the origin of life on Earth and possibly elsewhere.”
The supporting data and discussion from the original article are available via open access here.
And a more mainstream article on the topic in the Christian Science Monitor explaining in lay terms the differences between adenine and guanine versus hypoxanthine and xanthine can be found here.