Evolution of H2O, CO, and CO2 production in Comet C/2009 P1 Garradd during the 2011–2012 apparition

McKay, Adam; Cochran, A. L.; DiSanti, M. A.; Villanueva, Gerónimo; Russo, N. Dello; Vervack, R. J.; Morgenthaler, J. P.; Harris, Walter M.; Chanover, N. J.

doi:10.1016/j.icarus.2014.12.023

Cited by 42 publications

(31 citation statements)

References 51 publications

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“…Decock et al (2013) reported a mean value of 0.11 for their sample of 11 comets, which is about twice lower than what we measure for R2. However, both Decock et al (2013) and McKay et al (2015) reported that comets observed at larger heliocentric distance have higher values of the G/R ratio. For example, Decock et al (2013) The G/R ratio measured for R2 is thus consistent with the ratio measured for other comets observed at large heliocentric distances.…”

Section: [Ni] [Oi] and [Ci] Forbidden Atomic Linesmentioning

confidence: 97%

High resolution optical spectroscopy of the N₂-rich comet C/2016 R2 (PanSTARRS)

Opitom

Hutsemékers

Jehin

et al. 2019

A&A

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Context. Early observations of comet C/2016 R2 (PanSTARRS) have shown that the composition of this comet is very peculiar. Radio observations have revealed a CO-rich and HCN-poor comet and an optical coma dominated by strong emission bands of CO + and, more surprisingly, N + 2 . Aims. The strong detection of N + 2 in the coma of C/2016 R2 provided an ideal opportunity to measure the 14 N/ 15 N isotopic ratio directly from N + 2 for the first time, and to estimate the N 2 /CO ratio, which is an important diagnostic to constrain formation models of planetesimals, in addition to the more general study of coma composition. Methods. We obtained high resolution spectra of the comet in February when it was at 2.8 au from the Sun. We used the UVES spectrograph of the ESO VLT, complemented with narrow-band images obtained with the TRAPPIST telescopes. Results. We detect strong emissions from the ions N + 2 and CO + , but also CO + 2 , emission from the CH radical, and much fainter emissions of the CN, C 2 , and C 3 radicals which were not detected in previous observations of this comet. We do not detect OH or H 2 O + , and derive an upper limit of the H 2 O + /CO + ratio of 0.4, implying that the comet has a low water abundance. We measure a N + 2 /CO + ratio of 0.06 ± 0.01. The non-detection of NH 2 indicates that most of the nitrogen content of the comet lies within N 2 . Together with the high N + 2 /CO + ratio, this could indicate a low formation temperature of the comet, or that the comet is a fragment of a large differentiated Kuiper Belt object. The CO + 2 /CO + ratio is 1.1 ± 0.3. We do not detect 14 N 15 N + lines, and can only put a lower limit on the 14 N/ 15 N ratio measured from N + 2 of about 100, compatible with measurements of the same isotopic ratio for NH 2 and CN in other comets. Finally, in addition to the [OI] and [CI] forbidden lines, we detect for the first time the forbidden nitrogen lines [NI] doublet at 519.79 and 520.04 nm in the coma of a comet.

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Section: [Ni] [Oi] and [Ci] Forbidden Atomic Linesmentioning

confidence: 97%

High resolution optical spectroscopy of the N₂-rich comet C/2016 R2 (PanSTARRS)

Opitom

Hutsemékers

Jehin

et al. 2019

A&A

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“…Line ratios of [O i] may be used to determine the column density ratios of H 2 O, CO 2 , and CO (Delsemme 1980;Festou & Feldman 1981;Bhardwaj & Raghuram 2012). However, the release rates of [O i] in the relevant states as well as physical processes in the coma that may affect these lines are not yet completely understood, resulting in large uncertainties in the derived abundances (McKay et al 2012;DeCock et al 2013 and references therein).…”

Section: Did Co 2 Drive the Icy Grains?mentioning

confidence: 99%

“…Based on [O i] observations at Apache Point Observatory, McKay et al (2012) suggest constant CO 2 abundances of order 10%-15% within 2 AU pre-and post-perihelion. Finally, the Deep Impact spacecraft measured a CO 2 /H 2 O abundance of 8% at 2 AU post-perihelion (Feaga et al 2014).…”

Section: Did Co 2 Drive the Icy Grains?mentioning

confidence: 99%

THE EVOLVING ACTIVITY OF THE DYNAMICALLY YOUNG COMET C/2009 P1 (Garradd)

Bodewits

Farnham

A’Hearn

et al. 2014

ApJ

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We used the Ultraviolet-Optical Telescope on board Swift to observe the dynamically young comet C/2009 P1 (Garradd) from a heliocentric distance of 3.5 AU pre-perihelion until 4.0 AU outbound. At 3.5 AU pre-perihelion, comet Garradd had one of the highest dust-to-gas ratios ever observed, matched only by comet Hale-Bopp. The evolving morphology of the dust in its coma suggests an outburst that ended around 2.2 AU pre-perihelion. Comparing slit-based measurements and observations acquired with larger fields of view indicated that between 3 AU and 2 AU pre-perihelion a significant extended source started producing water in the coma. We demonstrate that this source, which could be due to icy grains, disappeared quickly around perihelion. Water production by the nucleus may be attributed to a constantly active source of at least 75 km 2 , estimated to be >20% of the surface. Based on our measurements, the comet lost 4 × 10 11 kg of ice and dust during this apparition, corresponding to at most a few meters of its surface. Even though this was likely not the comet's first passage through the inner solar system, the activity of Garradd was complex and changed significantly during the time it was observed.

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“…Comet researchers usually have to resort to remote observations. Numerous studies have been devoted to the direct observation of atomic oxygen lines [Morgenthaler et al, 2007;Cochran, 2008;McKay et al, 2015]. Photodissociation of H 2 O, CO 2 , and CO results in the release of an oxygen atom in an excited state, either O( 1 D) or O( 1 S).…”

Section: Introductionmentioning

confidence: 99%

Photochemistry of forbidden oxygen lines in the inner coma of 67P/Churyumov‐Gerasimenko

et al. 2016

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Observations of the green and red‐doublet emission lines have previously been realized for several comets. We present here a chemistry‐emission coupled model to study the production and loss mechanisms of the O(1S) and O(1D) states, which are responsible for the emission lines of interest for comet 67P/Churyumov‐Gerasimenko. The recent discovery of O2 in significant abundance relative to water 3.80 ± 0.85% within the coma of 67P has been taken into consideration for the first time in such models. We evaluate the effect of the presence of O2 on the green to red‐doublet emission intensity ratio, which is traditionally used to assess the CO2 abundance within cometary atmospheres. Model simulations, solving the continuity equation with transport, show that not taking O2 into account leads to an underestimation of the CO2 abundance within 67P, with a relative error of about 25%. This strongly suggests that the green to red‐doublet emission intensity ratio alone is not a proper tool for determining the CO2 abundance, as previously suggested. Indeed, there is no compelling reason why O2 would not be a common cometary volatile, making revision of earlier assessments regarding the CO2 abundance in cometary atmospheres necessary. The large uncertainties of the CO2 photodissociation cross section imply that more studies are required in order to better constrain the O(1S) and O(1D) production through this mechanism. Space weather phenomena, such as powerful solar flares, could be used as tools for doing so, providing additional information on a good estimation of the O2 abundance within cometary atmospheres.

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Evolution of H2O, CO, and CO2 production in Comet C/2009 P1 Garradd during the 2011–2012 apparition

Cited by 42 publications

References 51 publications

High resolution optical spectroscopy of the N₂-rich comet C/2016 R2 (PanSTARRS)

High resolution optical spectroscopy of the N₂-rich comet C/2016 R2 (PanSTARRS)

THE EVOLVING ACTIVITY OF THE DYNAMICALLY YOUNG COMET C/2009 P1 (Garradd)

Photochemistry of forbidden oxygen lines in the inner coma of 67P/Churyumov‐Gerasimenko

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Evolution of H2O, CO, and CO2 production in Comet C/2009 P1 Garradd during the 2011–2012 apparition

Cited by 42 publications

References 51 publications

High resolution optical spectroscopy of the N2-rich comet C/2016 R2 (PanSTARRS)

High resolution optical spectroscopy of the N2-rich comet C/2016 R2 (PanSTARRS)

THE EVOLVING ACTIVITY OF THE DYNAMICALLY YOUNG COMET C/2009 P1 (Garradd)

Photochemistry of forbidden oxygen lines in the inner coma of 67P/Churyumov‐Gerasimenko

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High resolution optical spectroscopy of the N₂-rich comet C/2016 R2 (PanSTARRS)

High resolution optical spectroscopy of the N₂-rich comet C/2016 R2 (PanSTARRS)