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Title: The photochemistry of pyrimidine in realistic astrophysical ices and the production of nucleobases

Nucleobases, together with deoxyribose/ribose and phosphoric acid, are the building blocks of DNA and RNA for all known life. The presence of nucleobase-like compounds in carbonaceous chondrites delivered to the Earth raises the question of an extraterrestrial origin for the molecules that triggered life on our planet. Whether these molecules are formed in interstellar/protostellar environments, in small parent bodies in the solar system, or both, is currently unclear. Recent experiments show that the UV irradiation of pyrimidine (C{sub 4}H{sub 4}N{sub 2}) in H{sub 2}O-rich ice mixtures that contain NH{sub 3}, CH{sub 3}OH, or CH{sub 4} leads to the formation of the pyrimidine-based nucleobases uracil, cytosine, and thymine. In this work, we discuss the low-temperature UV irradiation of pyrimidine in realistic astrophysical ice mixtures containing H{sub 2}O, CH{sub 3}OH, and NH{sub 3}, with or without CH{sub 4}, to search for the production of nucleobases and other prebiotic compounds. These experiments show the presence of uracil, urea, glycerol, hexamethylenetetramine, small amino acids, and small carboxylic acids in all samples. Cytosine was only found in one sample produced from ices irradiated with a higher UV dose, while thymine was not found in any sample, even after irradiation with a higher UV dose. Resultsmore » are discussed to evaluate the role of the photochemistry of pyrimidine in the inventory of organic molecules detected in meteorites and their astrophysical/astrobiological implications.« less
Authors:
; ;  [1]
  1. NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035 (United States)
Publication Date:
OSTI Identifier:
22370554
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 793; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMINO ACIDS; AMMONIA; ASTROPHYSICS; CHONDRITES; COSMOLOGY; CYTOSINE; DEOXYRIBOSE; DNA; GLYCEROL; METHANE; MOLECULES; PHOTOCHEMISTRY; PLANETS; RNA; SOLAR SYSTEM; STARS; THYMINE; ULTRAVIOLET RADIATION; WATER