Astronomy
The Search for Amino Acids in Cometary Material
Quick fact
NASA's Stardust mission found glycine—the simplest amino acid—in samples from comet Wild 2, and ESA's Rosetta spacecraft later detected glycine in the gas and dust around comet 67P/Churyumov-Gerasimenko.
Why this is interesting
You might think of comets as dirty snowballs, but they could be carriers of life's essential building blocks. Could the same material that built new homes also constructed the first proteins?
Read the full explanation
Understanding The Search for Amino Acids in Cometary Material
Amino acids are the molecular units that link together to form proteins, which do most of the work in living cells. For a long time, scientists wondered whether these molecules could form in space or only on planets. Comets, which formed at the dawn of the solar system and have remained largely frozen, offer a time capsule of early chemistry. When spacecraft fly by or orbit comets, they collect material from the comet's coma—the thin, transient atmosphere created as ice vaporizes near the Sun. By analyzing this material, scientists can test whether amino acids exist there. The discovery of glycine in two different comets suggests that such building blocks can form in space and might have been delivered to early Earth by incoming comets.
A deeper explanation
The detection of amino acids in comets isn't just about finding a molecule; it's about confirming its origin. Scientists use mass spectrometry to identify molecules, but contamination from Earth is a constant threat. To rule out contamination, they look at the ratio of carbon-13 to carbon-12 in the glycine molecules. Glycine formed in space shows a different isotopic signature than Earthly glycine. In the Stardust samples, the glycine had an unusual carbon-13 enrichment, indicating it was not terrestrial contamination. Such isotopic analyses, combined with carefully controlled collection methods, provide strong evidence that amino acids can form in comets. This reinforces the hypothesis that comets delivered these key precursors to Earth, potentially sparking the chemistry of life.