Astrobiology: An astronomer's perspective

Bergin, Edwin A.

doi:10.1063/1.4904143

Cited by 5 publications

(4 citation statements)

References 241 publications

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“…Deep in the cold miplane most molecules except H 2 , H + 3 and their isotopologs are frozen out onto the grains. There has been enormous observational and model activity in this field in recent years, see recent reviews 196,[216][217][218][219] . Highlights include the Spitzer and ground-based detections of hot (∼ 300 − 800 K) C 2 H 2 , HCN, H 2 O and CO 2 originating in the inner ∼1 AU of disks [220][221][222][223][224][225][226] .…”

Section: Protoplanetary Disksmentioning

confidence: 99%

Astrochemistry of dust, ice and gas: introduction and overview

Dishoeck

Ewine²

2014

Faraday Discuss.

138

102

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A brief introduction and overview of the astrochemistry of dust, ice and gas and their interplay is presented, aimed at non-specialists. The importance of basic chemical physics studies of critical reactions is illustrated through a number of recent examples. Such studies have also triggered new insight into chemistry, illustrating how astronomy and chemistry can enhance each other. Much of the chemistry in star- and planet-forming regions is now thought to be driven by gas-grain chemistry rather than pure gas-phase chemistry, and a critical discussion of the state of such models is given. Recent developments in studies of diffuse clouds and PDRs, cold dense clouds, hot cores, protoplanetary disks and exoplanetary atmospheres are summarized, both for simple and more complex molecules, with links to papers presented in this volume. In spite of many lingering uncertainties, the future of astrochemistry is bright: new observational facilities promise major advances in our understanding of the journey of gas, ice and dust from clouds to planets.Comment: Introductory paper for Faraday Discussions 168 conference, April 201

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Section: Protoplanetary Disksmentioning

confidence: 99%

Astrochemistry of dust, ice and gas: introduction and overview

Dishoeck

Ewine²

2014

Faraday Discuss.

138

102

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“…Nitrogen isotope fractionation is discussed in Section 4. More comprehensive reviews can be found in e.g., Caselli & Ceccarelli (2012), Bergin (2014), Ceccarelli et al (2014), and Willacy et al (2015).…”

Section: Introductionmentioning

confidence: 99%

Isotopic fractionation in interstellar molecules

Furuya

2017

Proc. IAU

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The level of isotopic fractionation in molecules provides insights into their formation environments and how they formed. In this article, we review hydrogen and nitrogen isotopic fractionation in low-mass star-forming regions. Interstellar molecules are significantly enriched in deuterium. The importance of the nuclear spin states of light species on deuterium fractionation and the usefulness of singly and doubly deuterated molecules as chemical tracers are discussed. Observations have revealed that molecules in prestellar cores are enriched in or depleted in 15 N depending on molecules. Compared with deuterium fractionation chemistry, our understanding of 15 N fractionation chemistry is not well established. We briefly discuss potential 15 N fractionation routes, i.e., isotopic-exchange reactions and isotopic selective photodissociation of N2. In addition, the selective freeze-out of 15 N atoms onto dust grains around the transition between N atoms and N2 is discussed as a potential mechanism that causes the depletion of 15 N in the gas phase.

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“…The resulting planetary atmosphere will hence be extremely metal-poor in the first place. Late bombardment with left-over planetesimals [ 14 , 15 ] will cause an element re-enrichment leading once more to a change of the atmospheric composition. The opacity of the atmosphere surrounding the planetary core plays an important role for the critical mass that inhibits further accretion [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

Disk Evolution, Element Abundances and Cloud Properties of Young Gas Giant Planets

Helling

Woitke

Rimmer

et al. 2014

Life

101

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We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. This gas will contain only traces of elements like C, N and O, because those elements have frozen out as ices. ProDiMo protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly. Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionization rate assumed. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The Drift cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying premordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, premordial element abundances are considered as suggested by disk models.

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Astrobiology: An astronomer's perspective

Cited by 5 publications

References 241 publications

Astrochemistry of dust, ice and gas: introduction and overview

Astrochemistry of dust, ice and gas: introduction and overview

Isotopic fractionation in interstellar molecules

Disk Evolution, Element Abundances and Cloud Properties of Young Gas Giant Planets

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