ESA’s Rosetta orbiter has detected volatile glycine and phosphorus in the fuzzy atmosphere of Comet 67P/Churyumov-Gerasimenko.

Amino acids are biologically important organic compounds containing carbon, oxygen, hydrogen and nitrogen, and form the basis of proteins.

Hints of glycine (C 2 H 5 NO 2 ), the simplest amino acid, were found in the dust samples returned to Earth in 2006 from Comet Wild-2 by NASA’s Stardust mission. However, possible terrestrial contamination of the samples made the analysis extremely difficult.

Now, the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) mass spectrometer on the Rosetta spacecraft has made direct, repeated detections of glycine in 67P/Churyumov-Gerasimenko’s atmosphere.

“This is the first unambiguous detection of glycine at a comet,” said Dr. Kathrin Altwegg, principal investigator of the ROSINA.

The measurements were made before 67P reached its closest point to the Sun – perihelion – in August 2015 in its 6.5 year orbit.

The first detection was made in October 2014 while Rosetta was just 6.2 miles (10 km) from the comet. The next occasion was during a flyby in March 2015, when it was 9.3-18.6 miles (15-30 km) from the nucleus.

Glycine is very hard to detect due to its non-reactive nature: it sublimates at slightly below 300 degrees Fahrenheit (150 degrees Celsius), meaning that little is released as gas from the comet’s surface or subsurface due to its cold temperatures. This accounts for the fact that Rosetta does not always detect it.

“We see a strong correlation of glycine to dust, suggesting that it is probably released from the grains’ icy mantles once they have warmed up in the coma, perhaps together with other volatiles,” Dr. Altwegg said.

“At the same time, we also detected certain other organic molecules that can be precursors to glycine, hinting at the possible ways in which it may have formed,” she added.

Unlike other amino acids, glycine is the only one that has been shown to be able to form without liquid water.

“The simultaneous presence of methylamine and ethylamine, and the correlation between dust and glycine, also hints at how the glycine was formed,” Dr. Altwegg said.

Another exciting detection made by ROSINA is of phosphorus, a key element in all known living organisms.

For example, it is found in the structural framework of DNA and in cell membranes, and it is used in transporting chemical energy within cells for metabolism.

“The multitude of organic molecules already identified by ROSINA, now joined by the exciting confirmation of fundamental ingredients like glycine and phosphorous, confirms our idea that comets have the potential to deliver key molecules for prebiotic chemistry,” said Dr. Matt Taylor, Rosetta project scientist.

“Demonstrating that comets are reservoirs of primitive material in the Solar System, and vessels that could have transported these vital ingredients to Earth, is one of the key goals of the Rosetta mission, and we are delighted with this result.”

The results were published online today in the journal Science Advances.

_____

Kathrin Altwegg et al. 2016. Prebiotic chemicals — amino acid and phosphorus — in the coma of comet 67P/Churyumov-Gerasimenko. Science Advances, vol. 2, no. 5, e1600285; doi: 10.1126/sciadv.1600285