Antifreeze in comet Hale-Bopp

Antifreeze in comet Hale-Bopp
Extrait du Observatoire de Paris centre de recherche et enseignement en astronomie et
astrophysique relevant du Ministère de l'Enseignement supérieur et de la Recherche.
https://www.obspm.fr/antifreeze-in-comet-hale-bopp.html
Antifreeze in comet Hale-Bopp
Date de mise en ligne : lundi 1er mars 2004
Observatoire de Paris centre de recherche et enseignement en astronomie et
astrophysique relevant du Ministère de l'Enseignement supérieur et de la
Recherche.
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Antifreeze in comet Hale-Bopp
From the analysis of archive spectra, some astronomers from Paris Observatory and their
collaborators, have discovered ethylene glycol in comet Hale-Bopp. This is the most complex
organic molecule identified to date in a comet.
Comet Hale-Bopp crédit : Nicolas Biver
The apparition of comet Hale-Bopp in 1997, an exceptionally bright comet, was an opportunity to discover many new
cometary molecules, from radio and infrared spectroscopic observations
A further study of its radio spectra just resulted in the identification of another molecule, ethylene glycol. Ethylene
glycol, whose chemical formula is HOCH2CH2OH, is a diol (i.e., this molecule has two alcohol functions). It is
commonly used as antifreeze in coolant fluids for car engines. It was recently identified in interstellar clouds in the
Galactic Centre. One of the spectra observed at IRAM showing three lines of ethylene glycol and lines of other
organic molecules.
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Antifreeze in comet Hale-Bopp
Une étude ultérieure des spectres radio vient d'aboutir à l'identification d'une nouvelle molécule, l'éthylène
glycol.
Ethylene glycol was identified from about ten lines in spectra of comet Hale-Bopp observed in spring 1997 with the
radio telescopes of the Institut de Radioastronomie Millimétrique (IRAM) (30-m radio telescope in Spain and Plateau
de Bure interferometer in the French Alps) and the Caltech Submillimeter Observatory (CSO) (10-m radio telescope
at Hawaii). From the same set of spectra, seven new molecules were previously identified, including formic acid
(HCOOH), formamide (NH2CHO), methyl formate (HCOOCH3) and acetaldehyde (CH3CHO). The identification of
ethylene glycol was possible only after the frequencies of the radio lines of this molecule were accurately known,
from laboratory measurements and theoretical modelling.With ten atoms, ethylene glycol is now the most complex
molecule identified in cometary atmospheres. Indeed, the space exploration of Halley's comet indicated the
presence of complex molecules composed of carbon, hydrogen, oxygen and nitrogen, especially in the organic
mantles coating cometary dust particles. But their very nature could not be precised. Observations show that there
are almost three molecules of ethylene glycol for one thousand molecules of water. Among organic molecules made
of carbon, hydrogen and oxygen, ethylene glycol is the most abundant after methyl alcohol (CH3OH) and
formaldehyde (H2CO). This suggests that still more complex species could be present in a significant amount.This
discovery conforts the analogy between interstellar matter and cometary material, which could have formed following
similar processes. Ethylene glycol and all other cometary molecules are indeed present in interstellar ices or in the
hot molecular cores of interstellar clouds.When impacting the early Earth at a sustained rate, comets could have
brought many constituants : part of the oceans' water, but also complex organic molecules, whose presence in
comets is attested by ethylene glycol. This seeding could have played a crucial role in the origin of life.This work was
done by J. Crovisier, D. Bockelée-Morvan, N. Biver, P. Colom (LESIA, Observatoire de Paris), D. Despois
(Observatoire de Bordeaux) and D.C. Lis (Californian Institute of Technology, USA).
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