While the idea that life on Earth started as a result of asteroid bombardment that brought crucial chemicals onto the planetary surface is not new, scientists working on the Rosetta mission have found that comets could play essentially the same role.
Writing in the journal Scientific American, a team of researchers from Europe and the US describe their discovery of glycine, methylamine, ethylamine, hydrogen cyanide, hydrogen sulphide and a key DNA component phosphorus in the coma (the gas and dust cloud that surrounds a comet as it warms) of the icy body known as 67P/Churyumov-Gerasimenko.
“It shows that even the very primitive bodies like comets contain a complex chemical soup, independent of [the] sun and Earth,” said lead author Kathrin Altwegg from the University of Bern. “They contain everything needed for life – except energy.”
In 2006, glycine has already been discovered in the material shed by the comet Wild-2, captured by NASA’s Stardust probe and brought back to Earth for analysis, but this marks the first time it’s been detected in space from a comet’s coma.
Altwegg and her team believe that glycine formed billions of years ago in the thin layers of ice surrounding dust grains in either the interstellar medium or the cloud of material that gave rise to the solar system (the so-called protosolar nebula) that eventually aggregated to form a comet.
Even more exciting than discovering what role comets might have played in the emergence of life on Earth is the idea that glycine can form in any protosolar nebula, potentially seeding other planets with the prerequisites for life.
Commenting on the study, Jason Dworkin, Chief of Astronomy at NASA’s Goddard Space Flight Centre said that while the data obtained by Rosini (the name given to Rosetta probe’s mass spectrometer) is bound to keep scientists occupied for years to come, the only way to really understand the makeup of comets is to bring chunks of these icy rocks back to Earth.
“These are the simplest, smallest biologically relevant compounds,” he said of the latest results. “To say more, and to look at the details of the chemistry, we need to look at a sample. We need to go to a comet, get a sample, bring it back to Earth and study it in a laboratory” – a task the agency plans to accomplish by launching its OSIRIS-Rex in September, set to return a sample of the asteroid 101955 Bennu to the surface for study.