The basic amino acid glycine was detected in the dust cloud surrounding Comet67P, seen here in a Rosetta mission image. | ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Using instruments aboard the European spacecraft Rosetta, scientists have detected glycine and phosphorus in the dusty envelope around the core of comet 67P/Churyumov-Gerasimenko, providing support for the idea that comets delivered key molecules for prebiotic chemistry throughout the solar system and to early Earth. The research appears in the 27 May issue of the journal Science Advances.
Scientists continue to debate certain aspects of the origins of life on Earth, among them the hypothesis that organic molecules were brought to the planet when small-bodied objects crashed into early Earth's terrestrial oceans. Although more than 100 molecules have been detected in galactic balls of dust and gas known as molecular clouds, glycine is not among the directly detected molecules, nor has the amino acid been identified previously in the more than 25 molecules found so far in the atmospheric envelope, known as the coma, that surrounds comets.
Glycine, the simplest form of amino acid and a main building block of proteins, has also gone undetected in two widely studied comets, Hale-Bopp and Hyakutake. The amino acid has been observed in a dust sample taken from the comet Wild 2, but only after the sample was brought back to Earth and analyzed using chemical ingredients, which raised concerns about possible contamination.
Kathrin Altwegg at the University of Bern in Switzerland and colleagues now report the first detection of glycine directly at the site of a comet, as part of the Rosetta mission that was chosen as Science's 2014 Breakthrough of Year.
By using a mass spectrometer called ROSINA on the Rosetta spacecraft, which detects and sorts incoming gas molecules by their mass as the spacecraft travels near a comet, Altwegg and colleagues were able to identify and measure specific molecules in the coma of comet 67P/Churyumov-Gerasimenko. ROSINA detected glycine, along with related precursor molecules methyl amine and ethyl amine.
So far, glycine is the only amino acid shown to form without liquid water; it is therefore likely to be the only amino acid in comets like 67P/Churyumov-Gerasimenko, where interactions with water are highly improbable, the authors say.
ROSINA also detected phosphorous, a crucial element in living organisms and found in the backbone of DNA and RNA, and in cell membranes. The presence of glycine, phosphorus, and other organic molecules seen in the coma of 67P/Churyumov-Gerasimenko supports the idea that comets played a pivotal role in the emergence of life on Earth.