Chalk up another win for the ‘life is ubiquitous’ school of thought. We now know that when the Stardust spacecraft passed through the gas and dust surrounding comet Wild 2 back in 2004, it captured samples that include glycine. Living things use glycine to make proteins, which made the preliminary detection of this amino acid a significant event, though one that had to be carefully analyzed. After all, terrestrial contamination could have accounted for the glycine gathered up by Stardust.
Image: The comet Wild 2 as imaged by the Stardust spacecraft. Credit: NASA/JPL.
Ensuing work, however, has ruled out the contamination scenario. The space-gathered samples show significantly more Carbon 13 than glycine from Earth, an isotopic marker that identifies the material as originating in the comet. That gets us back to a welcome thought, that life is common in the universe. Carl Pilcher (NASA Astrobiology Institute) has this to say:
“The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare.”
We’ve never found an amino acid on a comet before, but we’re now gaining evidence that points to the delivery of critical ingredients to the early Earth by comet and meteor impacts. Donald Brownlee (University of Washington) calls the discovery “a remarkable triumph that highlights the advancing capabilities of laboratory studies of primitive extraterrestrial materials.” More in this NASA news release. The paper is slated to appear in Meteoritics and Planetary Science.