Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)
Artikel i vetenskaplig tidskrift, 2016

The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30 m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January-3 February 2015. We detected 22 molecules and several isotopologues. The (H2O)-O-16 and (H2O)-O-18 production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of similar to 25%. The inferred isotope ratios in comet Lovejoy are O-16/O-18 = 499 +/- 24 and D/H = 1.4 +/- 0.4 x 10(-4) in water, S-32/S-34 = 24.7 +/- 3.5 in CS, all compatible with terrestrial values. The ratio C-12/C-13 = 109 +/- 14 in HCN is marginally higher than terrestrial and N-14/N-15 = 145 +/- 12 in HCN is half the Earth ratio. Several upper limits for D/H or C-12/C-13 in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.

radio lines: planetary systems

submillimeter: planetary systems

comets: individual: C/2014 Q2 (Lovejoy)

comets: individual: C/2012 F6 (Lemmon)

comets: general


N. Biver

GEPI - Galaxies, Etoiles, Physique, Instrumentation

R. Moreno

GEPI - Galaxies, Etoiles, Physique, Instrumentation

D. Bockelée-Morvan

GEPI - Galaxies, Etoiles, Physique, Instrumentation

A. Sandqvist

AlbaNova University Center

P. Colom

GEPI - Galaxies, Etoiles, Physique, Instrumentation

J. Crovisier

GEPI - Galaxies, Etoiles, Physique, Instrumentation

D. C. Lis

CNRS Centre National de la Recherche Scientifique

J. Boissier

Institut de RadioAstronomie Millimetrique (IRAM)

V. Debout

GEPI - Galaxies, Etoiles, Physique, Instrumentation

G. Paubert

Instituto de Radioastronomia Milimetrica

S. Milam

NASA Goddard Space Flight Center

Åke Hjalmarson

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

S. Lundin

OHB Sweden

T. Karlsson

OHB Sweden

M. Battelino

OHB Sweden

U. Frisk

Omnisys Instruments AB

Donal Murtagh

Chalmers, Rymd- och geovetenskap, Global miljömätteknik och modellering

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 589 Art. no. A78- A78


Astronomi, astrofysik och kosmologi


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