The Ice Survey Opportunity of ISO

Dartois, E.

doi:10.1007/1-4020-3844-5_13

Cited by 14 publications

(20 citation statements)

References 70 publications

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“…(1) A CH 3 source is needed. CH 3 OH and CH 4 are both seen in interstellar ices (Allamandola et al, 1992;Gibb et al, 2004;Dartois, 2005) and are valid sources of CH 3 radicals. CH 3 OH is typically much more abundant than CH 4 in interstellar ices, but the results of our experiments suggest that CH 4 is a more efficient source of CH 3 radicals than CH 3 OH.…”

Section: Formation Of Thyminementioning

confidence: 99%

“…Both CH 3 OH and CH 4 are important components of interstellar ices (Allamandola et al, 1992;Gibb et al, 2004;Dartois, 2005) and may react with pyrimidine upon exposure to UV radiation to form nucleobases, including thymine, although in the case of CH 4 an additional oxygen source would be required. To study the possibility of methyl photoaddition to pyrimidine, we performed UV photolysis experiments, under astrophysical conditions, of several ices consisting of pyrimidine mixed with CH 3 OH, H 2 O + CH 3 OH, CH 4 , and H 2 O + CH 4 in different relative proportions.…”

Section: Introductionmentioning

confidence: 99%

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Thymine and Other Prebiotic Molecules Produced from the Ultraviolet Photo-Irradiation of Pyrimidine in Simple Astrophysical Ice Analogs

et al. 2013

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The informational subunits of RNA or DNA consist of substituted N-heterocyclic compounds that fall into two groups: those based on purine (C₅H₄N₄) (adenine and guanine) and those based on pyrimidine (C₄H₄N₂) (uracil, cytosine, and thymine). Although not yet detected in the interstellar medium, N-heterocycles, including the nucleobase uracil, have been reported in carbonaceous chondrites. Recent laboratory experiments and ab initio calculations have shown that the irradiation of pyrimidine in ices containing H₂O, NH₃, or both leads to the abiotic production of substituted pyrimidines, including the nucleobases uracil and cytosine. In this work, we studied the methylation and oxidation of pyrimidine in CH₃OH:pyrimidine, H₂O:CH₃OH:pyrimidine, CH₄:pyrimidine, and H₂O:CH₄:pyrimidine ices irradiated with UV photons under astrophysically relevant conditions. The nucleobase thymine was detected in the residues from some of the mixtures. Our results suggest that the abundance of abiotic thymine produced by ice photolysis and delivered to the early Earth may have been significantly lower than that of uracil. Insofar as the delivery of extraterrestrial molecules was important for early biological chemistry on early Earth, these results suggest that there was more uracil than thymine available for emergent life, a scenario consistent with the RNA world hypothesis.

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Section: Formation Of Thyminementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thymine and Other Prebiotic Molecules Produced from the Ultraviolet Photo-Irradiation of Pyrimidine in Simple Astrophysical Ice Analogs

et al. 2013

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“…Solid state formaldehyde has long been identified as a key constituent within the interstellar/cometary grains in addition to ubiquitous water along with minor amounts of methane, ammonia, and carbon dioxide. The molecular abundance of formaldehyde within the icy mantles varies from 1% to 6% relative to water in several high-and low-mass protostars (Dartois 2005;Boogert et al 2008) or hot corinos (Maret et al 2004). These icy mantles are constantly being bombarded with high-energy galactic cosmic rays and/or exposed to the interstellar UV field.…”

Section: Astrophysical Significancementioning

confidence: 99%

Radical-induced chemistry from VUV photolysis of interstellar ice analogues containing formaldehyde

Butscher

Duvernay

Danger

et al. 2016

A&A

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Surface processes and radical chemistry within interstellar ices are increasingly suspected to play an important role in the formation of complex organic molecules (COMs) observed in several astrophysical regions and cometary environments. We present new laboratory experiments on the low-temperature solid state formation of complex organic molecules -glycolaldehyde, ethylene glycol, and polyoxymethylene -through radical-induced reactivity from VUV photolysis of formaldehyde in water-free and water-dominated ices. Radical reactivity and endogenous formation of COMs were monitored in situ via infrared spectroscopy in the solid state and post photolysis with temperature programmed desorption (TPD) using a quadripole mass spectrometer. We show the ability of free radicals to be stored when formed at low temperature in water-dominated ices, and to react with other radicals or on double bonds of unsaturated molecules when the temperature increases. It experimentally confirms the role of thermal diffusion in radical reactivity. We propose a new pathway for formaldehyde polymerisation induced by HCO radicals that might explain some observations made by the Ptolemy instrument on board the Rosetta lander Philae. In addition, our results seem to indicate that H-atom additions on H 2 CO proceed preferentially through CH 2 OH intermediate radicals rather than the CH 3 O radical.

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“…This dust is composed of a silicate core embedded in an ice layer essentially composed of water with traces of other molecules such as CH 3 OH, CO, CO 2 , NH 3 , and H 2 CO . Depending on the proximity of a star, the grains can chemically evolve because of thermal or photochemical effects.…”

Section: Introductionmentioning

confidence: 99%