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ABSTRACT: Isotopic abundance ratios are excellently suited to probe the origin of solar system matter. We review the recent measurements
of the isotopic ratios of the light elements (D/H, 12C/13C, 16O/18O, 14N/15N, 32S/34S) in cometary dust and gas and discuss briefly their implications. Special emphasis will be put on the determinations and
progress performed in the field over the past years thanks to high resolution spectroscopy of cometary comae obtained with
the ESO Very Large Telescope. Future perspectives from space missions and ground-based observations with new large and extremely
large telescopes operating in the optical, infrared and submillimeter wavelengths will be presented.
Earth Moon and Planets 04/2012; 105(2):167-180. · 0.67 Impact Factor
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E. Jehin,
D. Bockelée-Morvan,
N. Dello Russo,
J. Manfroid,
D. Hutsemékers,
H. Kawakita,
H. Kobayashi,
R. Schulz,
A. Smette,
J. Stüwe, [......], C. Arpigny,
N. Biver,
A. Cochran,
J. Crovisier,
P. Magain,
H. Rauer,
H. Sana,
R. J. Vervack,
H. Weaver,
J.-M. Zucconi
[show abstract]
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ABSTRACT: We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very
Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space
missions. From high resolution optical spectroscopy of the CN (0,0) 388nm and NH2 (0,9,0) 610nm bands using UVES at UT2 we determined 12C/13C=90±10 and 14N/15N=150±20 in CN and we derived a nuclear spin temperature of NH3 of 29±1K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit
spectroscopy with FORS1 at UT2 we determined the CN, C3 and C2 production rates and the parent and daughter scale lengths up to 5.2 105km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and
mixing ratios of H2O, HCN, C2H2, CH4, C2H6, and CH3OH.
Earth Moon and Planets 04/2012; 105(2):343-349. · 0.67 Impact Factor
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ABSTRACT: Our aim is to determine the isotopic ratios {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} in a variety of comets and link these measurements to the formation and evolution of the solar system. The {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} isotopic ratios are measured {for} the CN radical by means of high-resolution optical spectra of the R branch of the B-X (0,0) violet band. {23 comets from different dynamical classes} have been observed, sometimes at various heliocentric {and nucleocentric} distances, in order to estimate possible variations of the isotopic ratios in parent molecules. The {$^{12}$C/$^{13}$C}{} and {$^{14}$N/$^{15}$N}{} isotopic ratios in CN are remarkably constant (average values of, respectively, $91.0\pm3.6$ and $147.8\pm5.7$) within our measurement errors, for all comets whatever their origin or heliocentric distance. While the carbon isotopic ratio does agree with the terrestrial value (89), the nitrogen ratio is a factor of two lower than the terrestrial value (272), indicating a fractionation in the early solar system, or in the protosolar nebula, common to all the comets of our sample. This points towards a common origin of the comets independently of their birthplaces, and a relationship between HCN and CN. Comment: 54 pages
07/2009;
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ABSTRACT: New independent constraints on the amount of water delivered to Earth by comets are derived using the 15N/14N isotopic ratio, measured to be roughly twice as high in cometary CN and HCN as in the present Earth. Under reasonable assumptions, we find that no more than a few percent of Earth's water can be attributed to comets, in agreement with the constraints derived from D/H. Our results also suggest that a significant part of Earth's atmospheric nitrogen might come from comets. Since the 15N/14N isotopic ratio is not different in Oort-cloud and Kuiper-belt comets, our estimates apply to the contribution of both types of objects. Comment: Accepted for publication in ICARUS
06/2009;
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ABSTRACT: High-resolution (R ~ 60,000) spectra of the CN B 2Σ+-X 2Σ+ (0, 0) band (near 3880 Å) in the Halley-type comet 122P/1995 S1 de Vico (with a period of 74 yr) and the "intermediate-period" comet 153P/2002 C1 Ikeya-Zhang (P ~ 370 yr) were obtained with the 2dcoudé spectrograph at the 2.7 m Harlan J. Smith telescope of the McDonald Observatory. The comets were within 1 AU from the Sun (0.66 and 0.92 AU, respectively) at the time of the observations. While the measured 12C/13C isotope ratios of both comets (90 ± 10 and 90 ± 25, respectively) are in very good agreement with the solar system value, the 14N/15N ratios (140 ± 20 and 170 ± 50, respectively) are approximately half the value in Earth's atmosphere. The similarity is striking between these ratios and those obtained recently for two other long-period Oort Cloud comets, C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR). While these optical determinations of 14N/15N are consistent with each other, they disagree with those obtained in comet Hale-Bopp from submillimeter measurements of HCN, generally believed to be the main parent of CN. This puzzling difference points toward the existence of (an)other unknown parent(s) of CN, with an even higher 15N excess. Organic compounds like those found in interplanetary dust particles are good candidates.
The Astrophysical Journal 12/2008; 613(2):L161. · 6.02 Impact Factor
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D. Bockelée-Morvan,
N. Biver,
E. Jehin,
A. L. Cochran,
H. Wiesemeyer,
J. Manfroid,
D. Hutsemékers, C. Arpigny,
J. Boissier,
W. Cochran,
P. Colom,
J. Crovisier,
N. Milutinovic,
R. Moreno,
J. X. Prochaska,
I. Ramirez,
R. Schulz,
and J.-M. Zucconi
[show abstract]
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ABSTRACT: From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of 2007 October 24, we derive 14N/15N = 139 ± 26 in HCN and 14N/15N = 165 ± 40 in CN, establishing that HCN has the same nonterrestrial isotopic composition as CN. The same conclusion is obtained for the long-period comet C/1995 O1 (Hale-Bopp) after a reanalysis of previously published measurements. These results are compatible with HCN being the prime parent of CN in cometary atmospheres. The15N excess relative to the Earth's atmospheric value indicates that N-bearing volatiles in the solar nebula underwent important N isotopic fractionation at some stage of solar system formation. HCN molecules never isotopically equilibrated with the main nitrogen reservoir in the solar nebula before being incorporated in Oort Cloud and Kuiper Belt comets. The 12C/13C ratios in HCN and CN are measured to be consistent with the terrestrial value.
The Astrophysical Journal 12/2008; 679(1):L49. · 6.02 Impact Factor
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ABSTRACT: The 16OH/18OH and OD/OH isotope ratios are measured in the Oort-Cloud comet C/2002 T7 (LINEAR) through ground-based observations of the OH ultraviolet bands at 3063 A (0,0) and 3121 A (1,1) secured with the Very Large Telescope (VLT) feeding the Ultraviolet-Visual Echelle Spectrograph (UVES). From the 16OH/18OH ratio, we find 16O/18O = 425 +/- 55, equal within the uncertainties to the terrestrial value and to the ratio measured in other comets, although marginally smaller. We also estimate OD/OH from which we derive D/H = 2.5 +/- 0.7 10-4 in water. This value is compatible with the water D/H ratios evaluated in other comets and marginally higher than the terrestrial value. Comment: Accepted for publication in A&A Letters
09/2008;
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ABSTRACT: We report on observations of comet 9P/Tempel 1 carried out before, during, and after the NASA DEEP IMPACT event (UT July 4), with the optical spectrometers UVES and HIRES mounted on the telescopes Kueyen of the ESO VLT (Chile) and Keck 1 on Mauna Kea (Hawaii), respectively. A total observing time of about 60 hours, distributed over 15 nights around the impact date, allowed us (i) to find a periodic variation of 1.709 +/- 0.009 day in the CN and NH flux, explained by the presence of two major active regions; (ii) to derive a lifetime > ~ 5 x 10^4 s for the parent of the CN radical from a simple modeling of the CN light curve after the impact; (iii) to follow the gas and dust spatial profiles evolution during the 4 hours following the impact and derive the projected velocities (400 m/s and 150 m/s respectively); (iv) to show that the material released by the impact has the same carbon and nitrogen isotopic composition as the surface material (12C/13C = 95 +/- 15 and 14N/15N = 145 +/- 20). Comment: Accepted for publication in ApJ Letters
03/2006;
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K J Meech,
N Ageorges,
M F A'Hearn, C Arpigny,
A Ates,
J Aycock,
S Bagnulo,
J Bailey,
R Barber,
L Barrera, [......],
J-H Wu,
T Yamashita,
B Yang,
Y-B Yang,
S Yokogawa,
A C Zook,
A Zauderer,
X Zhao,
X Zhou,
J-M Zucconi
[show abstract]
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ABSTRACT: On 4 July 2005, many observatories around the world and in space observed the collision of Deep Impact with comet 9P/Tempel 1 or its aftermath. This was an unprecedented coordinated observational campaign. These data show that (i) there was new material after impact that was compositionally different from that seen before impact; (ii) the ratio of dust mass to gas mass in the ejecta was much larger than before impact; (iii) the new activity did not last more than a few days, and by 9 July the comet's behavior was indistinguishable from its pre-impact behavior; and (iv) there were interesting transient phenomena that may be correlated with cratering physics.
Science 11/2005; 310(5746):265-9. · 31.20 Impact Factor
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K. ~J. Meech,
N. Ageorges,
M. ~F. A'Hearn, C. Arpigny,
A. Ates,
J. Aycock,
S. Bagnulo,
J. Bailey,
R. Barber,
L. Barrera, [......],
J. -H. Wu,
T. Yamashita,
B. Yang,
Y. -B. Yang,
S. Yokogawa,
A. ~C. Zook,
A. Zauderer,
X. Zhao,
X. Zhou,
J. -M. Zucconi
Science. 10/2005; 310:265-269.
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ABSTRACT: The 12C14N/12C15N and 12C14N/13C14N isotopic ratios are determined for the first time in a Jupiter-family comet, 88P/1981 Q1 Howell, and in the chemically peculiar Oort Cloud comet C/1999 S4 (LINEAR). By comparing these measurements to previous ones derived for six other Oort Cloud comets (including one of Halley-type), we find that both the carbon and nitrogen isotopic ratios are constant within the uncertainties. The mean values are 12C/13C ~ 90 and 14N/15N \~ 145 for the eight comets. These results strengthen the view that CN radicals originate from refractory organics formed in the protosolar molecular cloud and subsequently incorporated in comets. Comment: Accepted for publication in A&A letters
08/2005;
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ABSTRACT: The 12C14N/12C15N and 12C14N/13C14N isotopic ratios have been determined in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT) and C/2003 K4 (LINEAR) at heliocentric distances of, respectively, 2.7, 3.7 and 2.6 AU. These ratios have also been measured at r ~ 1 AU. No significant differences were found between all determinations, nor with the value obtained for other comets. If confirmed, the discrepancy between the nitrogen isotopic ratios from optical and millimeter measurements on CN and HCN would rule out HCN as a major parent of the cometary CN radicals. Comment: Accepted for publication in Astronomy ans Astrophysics
01/2005;
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ABSTRACT: We report the first detection of atomic deuterium (D) emission in a
comet. On three different dates (2004 April 24.3, 26.9, and 28.8 UT),
the D Lyman-α line at 1215.34 Å was clearly detected (S/N
˜6) during observations of comet C/2001 Q4 (NEAT) using the Space
Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope
(HST). During that time, the comet's heliocentric distance varied from
1.04 AU to 1.00 AU, the geocentric distance ranged from 0.54 AU to 0.39
AU, and the water production rate was ˜1.9 × 1029
s-1. The STIS echelle grating E140H was used with a 0.''2
× 6'' slit, which provides a velocity resolution of ˜5.5 km
s-1 for a spatially uniform emission, to measure the D line
simultaneously with the atomic hydrogen (H) Lyman-α line, both of
which were cleanly separated from the terrestrial airglow H and D
emissions. Since the observations were made with a relatively small
aperture, detailed modeling is required to convert the observed D and H
column densities into a cometary D/H ratio, which can then be compared
to the deuterium abundance in other comets, in the earth's water, and in
the interstellar medium. The derivation of the H production rate is
relatively straightforward, but uncertainty in the photolysis pathways
for HDO, the presumed primary source of D in the inner coma, and of the
spatial distribution of D, make the derivation of an accurate D
production rate problematic. We present our current best estimate for
the D/H ratio in C/NEAT and discuss the prospects for improving the
accuracy of that determination. We also briefly report on an HST search
for D emission from C/2002 T7 (LINEAR), conducted during 2004 June 6-7
UT.
10/2004; 36:1120.
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H A Weaver,
Z Sekanina,
I Toth,
C E Delahodde,
O R Hainaut,
P L Lamy,
J M Bauer,
M F A'Hearn, C Arpigny,
M R Combi, [......],
P D Feldman,
M C Festou,
R Hook,
L Jorda,
M S Keesey,
C M Lisse,
B G Marsden,
K J Meech,
G P Tozzi,
R West
[show abstract]
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ABSTRACT: At least 16 fragments were detected in images of comet C/1999 S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST) and on 6 August with the Very Large Telescope (VLT). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass in the observed fragments was about 2 x 10(9) kilograms. The comet's dust tail, which was the most prominent optical feature in August, was produced during a major fragmentation event, whose activity peaked on UT 22.8 +/- 0.2 July 2000. The mass of small particles (diameters less than about 230 micrometers) in the tail was about 4 x 10(8) kilograms, which is comparable to the mass contained in a large fragment and to the total mass lost from water sublimation after 21 July 2000 (about 3 x 10(8) kilograms). HST spectroscopic observations during 5 and 6 July 2000 demonstrate that the nucleus contained little carbon monoxide ice (ratio of carbon monoxide to water is less than or equal to 0.4%), which suggests that this volatile species did not play a role in the fragmentation of C/1999 S4 (LINEAR).
Science 06/2001; 292(5520):1329-33. · 31.20 Impact Factor
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ABSTRACT: The abundance ratios of stable isotopes of the light elements in comets
may provide clues of cosmogonical significance. Measuring isotopic
ratios in an optical cometary spectrum is, however, a rather difficult
task for different reasons. Such measurements require, in particular,
very high spectral resolution and are feasible so far only on bright
objects. In 1997 we observed comet Hale-Bopp with the 2.6 m Nordic
Optical Telescope on La Palma, Canary Islands, with a view to estimating
the 12C/13C abundance ratio. About twenty
high-resolution (λ /Δ λ ~ 70000) spectra of the
strong CN Violet (0,0) band were secured with the SOFIN spectrograph
from 7 to 13 April. The heliocentric and geocentric distances of the
comet were then close to 0.9 AU and 1.4 AU, respectively. While the data
do show the expected lines of the 13C14N isotopic
molecule, we have been surprised to find in addition a number of very
weak features, which are real and turn out to be positioned very near to
the theoretical wavelengths of lines pertaining to the R branch of
12C15N. After a short description of the reduction
and analysis of the data our paper discusses the results derived for
12C/13C and 14N/15N as well
as their possible implications. We also present a brief review of the
carbon and nitrogen isotopic ratios in various solar system objects and
consider the question whether any nucleosynthesis site(s) is (are) known
where pairs of values similar to those we measure in comet Hale-Bopp
could be produced.
09/2000; 32:1074.
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08/1999; 31:1124.
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ABSTRACT: The compositional evolution of the coma of Rosetta target comet
46P/Wirtanen was studied along its pre-perihelion orbit. At 2.34 AU the
first gaseous species, CN and C_3, were detected. C_2 and NH_2 arose at
2.0 AU. The production rate curves of gas and dust show a steep increase
between 1.8 AU and 1.6 AU indicating a distinct change of the outgassing
conditions. The C_2 production increases more rapidly with decreasing
solar distance than CN. As one consequence the C_2/CN ratio strongly
varies with heliocentric distance. Due to this variation a
classification of 46P/Wirtanen by the taxonomy introduced by A'Hearn et
al. (\cite{AMSOB}) distinguishing comets with typical abundance ratios
from carbon-chain depleted comets, is impossible. It would be classified
as depleted beyond about 1.6 AU whereas it would be designated typical
at smaller distances. The knowledge of the unexpected changes in the
activity curves of 46P/Wirtanen will help to optimize the Rosetta
mission scenario in particular with regard to science operations. based
on observations obtained at ESO La Silla within ESO programmes No.
57.F-0290 and 58.F-0413
Astronomy and Astrophysics 06/1998; 335:L46-L49. · 4.59 Impact Factor
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Science 10/1997; 277(5331):1526-7. · 31.20 Impact Factor
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[show abstract]
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ABSTRACT: Analysis of Hubble Space Telescope (HST) images of comet Hale-Bopp (C/1995 O1) suggests that the effective diameter of the nucleus is between 27 to 42 kilometers, which is at least three times larger than that of comet P/Halley. The International Ultraviolet Explorer and HST spectra showed emissions from OH (a tracer of H2O) and CS (a tracer of CS2) starting in April 1996, and from the CO Cameron system (which primarily traces CO2) starting in June 1996. The variation of the H2O production rate with heliocentric distance was consistent with sublimation of an icy body near its subsolar point. The heliocentric variation in the production rates of CS2 and dust was different from that of H2O, which implies that H2O sublimation did not control the CS2 or dust production during these observations.
Science 04/1997; 275(5308):1900-4. · 31.20 Impact Factor
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[show abstract]
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ABSTRACT: The activity of comet Hale-Bopp (C/1995 O1) was monitored monthly by optical imaging and long-slit spectroscopy of its dust and gas distribution over heliocentric distances of 4.6 to 2.9 astronomical units. The observed band intensities of the NH2 radical and the H2O+ ion cannot be explained by existing models of fluorescence excitation, warranting a reexamination of the corresponding production rates, at least at large heliocentric distances. Comparing the production rate of the CN radical to its proposed parent, HCN, shows no evidence for the need of a major additional source for CN in Hale-Bopp at large heliocentric distances. The dust and CN production rates are consistent with a significant amount of sublimation occurring from icy dust grains surrounding Hale-Bopp.
Science 04/1997; 275(5308):1909-12. · 31.20 Impact Factor
