Cometary cocktail: Lovejoy has ethanol, glycolaldehyde and other organics

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  • Published: Nov 1, 2015
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
thumbnail image: Cometary cocktail: Lovejoy has ethanol, glycolaldehyde and other organics

Organic cocktail

Comet Lovejoy is releasing vast quantities of two organic compounds - ethanol and glycine - its wake, according to an international spectroscopic study. This is the first time ethanol has been identified in a comet and the presence of this as well as glycine adds to the growing evidence that comets may have been the source of complex organic molecules necessary for the emergence of life on Earth.

Comet Lovejoy is releasing vast quantities of at least two organic compounds - ethanol and glycolaldehyde - in its wake, according to an international spectroscopic study. This is the first time ethanol has been identified in a comet and the presence of this as well as glycolaldehyde adds to the growing evidence that comets may have been the source of complex organic molecules necessary for the emergence of life on Earth.

Comet Lovejoy, also known as comet C/2014 Q2 was photographed here on 12th February 2015 50 kilometres south of Paris by Fabrice Noel. "We found that comet Lovejoy was releasing as much alcohol as in at least 500 bottles of wine every second during its peak activity," explains Nicolas Biver of the Paris Observatory, France, who is lead author on the paper reporting the discovery in the journal Science Advances. The team found 21 different organic molecules in gas streaming from the comet, including ethanol and glycolaldehyde.

Frozen fossils

Astronomers consider comets to be the frozen remnants of debris present in the accretion disc that formed the solar system 4.6 billion years ago. They are of key interest today not only for the clues they might harbour as to the processes involved in that formation because their contents are essentially locked in that primordial time, but also because they may also contain clues as to the origins of organic chemistry that potentially was the fuel that fired up life on Earth following truly ancient cometary impact. Most comets orbit in the frigid zones far from the sun but occasional gravitational disturbance will pull them into a new orbit that sets them on much harsher course bringing them close to the sun, where they heat up and release gases. It is at this point in a comet's history that science can take a look and perhaps unearth the composition of these icy objects from deep-time.

Lovejoy was one of the brightest and most active comets since comet Hale-Bopp in 1997. It passed closest to the sun on the 30th January 2015 and at that time was releasing water at a rate of 20 tonnes per second. The team observed the atmosphere of the comet around this time when it was brightest and most active and in particular its microwave glow - due to excitation in that spectroscopic range - using the 30-metre diameter radio telescope at Pico Veleta in the Sierra Nevada Mountains of Spain.

Cometary analysis

The detectors on the telescope can analyse a wide range of frequencies at once, allowing the team to determine the types and amounts of many different molecules in the comet despite a short observation period. The discovery of complex organic molecules in Lovejoy adds credence to their theoretical "seeds of life" status.

"The result definitely promotes the idea that comets carry very complex chemistry," explains Stefanie Milam of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "During the Late Heavy Bombardment that ended about 3.8 billion years ago, when many comets and asteroids were blasting into Earth and we were getting our first oceans, life didn't have to start with just simple molecules like water, carbon monoxide, and nitrogen. Instead, life had something that was much more sophisticated on a molecular level. We're finding molecules with multiple carbon atoms. So now you can see where sugars start forming, as well as more complex organics such as amino acids - the building blocks of proteins - or nucleobases, the building blocks of DNA. These can start forming much easier than beginning with molecules with only two or three atoms." Many of these more complex molecules were also spotted by the Philae lander from the Rosetta spacecraft as it landed on comet 67P/Churyumov-Gerasimenko in November 2014.

"The next step is to see if the organic material being found in comets came from the primordial cloud that formed the solar system or if it was created later on, inside the protoplanetary disk that surrounded the young sun," explains team member Dominique Bockelée-Morvan of the Paris Observatory. "We will pursue this kind of molecular survey in other bright comets, to assess the relative abundance of ethyl alcohol and glycolaldehyde and search for more molecules," Biver told SpectroscopyNOW. Indeed, while the team did not detect glycine in comet Lovejoy, they did look for it and will have an upper limit on its abundance later. "We have more data on this comet (isotopic ratios, limits on the abundances of other interesting molecules) that we will publish soon," Biver told us. Glycine was previously reported as being present in samples from comet 81P/Wild 2 (Stardust mission) but is yet to be confirmed in other comets.

Related Links

Sci Adv 2015, 1(9), e1500863: "Ethyl alcohol and sugar in comet C/2014 Q2 (Lovejoy)"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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