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

Journal Article · Wed Oct 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/793/2/125· OSTI ID:22370554

Nuevo, Michel; Materese, Christopher K.

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. Results 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.

• OSTI ID: 22370554
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 793; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMINO ACIDS
AMMONIA
ASTROPHYSICS
CHONDRITES
COSMOLOGY
CYTOSINE
DEOXYRIBOSE
DNA
GLYCEROL
METHANE
MOLECULES
PHOTOCHEMISTRY
PLANETS
RNA
SOLAR SYSTEM
STARS
THYMINE
ULTRAVIOLET RADIATION
WATER