It is possible to form glycine, the simplest amino acid, in the star nurseries of interstellar clouds. Glycine’s development in such an inhospitable environment had previously been theorized. Most notably, glycine has been observed in samples of comet Wild 2 returned from the Stardust mission as well as in observations of the coma of comet 67P/Churymov-Gerasimenko. Since comets formed together with the solar system from the same original starting material, they are a window into that solar system in its earlier years. Glycine has been seen in those windows, so scientists theorized that it might have formed in the base material that both comets and the solar system itself share.
A team led by Sergio Ioppolo of Queen Mary University set out to see if they could form glycine in the conditions of the interstellar gas clouds where stars, planets, and comets are born. They constructed an ultra-high vacuum chamber, lowered the temperature down to between 10-20 degrees Kelvin to mimic the conditions in dark interstellar gas clouds. Subsequently, they placed chemicals known to be present in those interstellar clouds inside the vacuum chamber, such as carbon monoxide, ammonia, and methane. Then they exposed the frozen chemicals to unbound atoms, that sparked chemistry similar to that which takes place under dark cloud conditions. Like magnets clicking together, the atoms broke apart the existing chemicals and allowed their constituents to recombine in unique ways.
The work by Dr. Ioppolo and his team demonstrated that glycine can form under the conditions that occur in these dark corners of space. Similar to the Sun, most of the material in dark clouds consists of helium and hydrogen. Hydrogen, can exist as a molecule, H2, and as an unbound atom.
The unbound atom is highly reactive, and initiates chemistry with almost anything it comes across. It combines with other atoms build up molecules such as CH4 (methane), NH3 (ammonia). In the intermediate stages of this hydrogen bombardment, the precursor chemicals CH3 and NH2 may react to form CH3NH2, methylamine. Methylamine is a precursor to glycine and has been found abundantly in comet 67P. This finding most likely directly leads to the finding of the abundance of glycine in the same comet.
In experiments described in the recent paper, the specifics of these reactions were investigated, and the abundance of glycine formed in these reactions was calculated. The calculation shows that the amount of glycine that is formed is enough to enrich planets like the early Earth with prebiotic molecules to facilitate the origins of life.
Now that the chemical proof of concept has been shown, scientists can turn to the numerous implications this work has for both existing theories and future studies. The paper shows that it is possible that the building blocks of life can result from natural processes taking place before star formation, enriching the raw materials of planets with the essential building blocks of life. Although these molecules may not survive the harsh events of planet formation, the fact that they may be present in the raw materials of stars and planets suggests their abundance is widespread throughout the universe.