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Title: Evolution of Morphological and Physical Properties of Laboratory Interstellar Organic Residues with Ultraviolet Irradiation

Abstract

Refractory organic compounds formed in molecular clouds are among the building blocks of the solar system objects and could be the precursors of organic matter found in primitive meteorites and cometary materials. However, little is known about the evolutionary pathways of molecular cloud organics from dense molecular clouds to planetary systems. In this study, we focus on the evolution of the morphological and viscoelastic properties of molecular cloud refractory organic matter. We found that the organic residue, experimentally synthesized at ∼10 K from UV-irradiated H{sub 2}O-CH{sub 3}OH-NH{sub 3} ice, changed significantly in terms of its nanometer- to micrometer-scale morphology and viscoelastic properties after UV irradiation at room temperature. The dose of this irradiation was equivalent to that experienced after short residence in diffuse clouds (≤10{sup 4} years) or irradiation in outer protoplanetary disks. The irradiated organic residues became highly porous and more rigid and formed amorphous nanospherules. These nanospherules are morphologically similar to organic nanoglobules observed in the least-altered chondrites, chondritic porous interplanetary dust particles, and cometary samples, suggesting that irradiation of refractory organics could be a possible formation pathway for such nanoglobules. The storage modulus (elasticity) of photo-irradiated organic residues is ∼100 MPa irrespective of vibrational frequency, a valuemore » that is lower than the storage moduli of minerals and ice. Dust grains coated with such irradiated organics would therefore stick together efficiently, but growth to larger grains might be suppressed due to an increase in aggregate brittleness caused by the strong connections between grains.« less

Authors:
; ; ; ; ;  [1]; ; ; ; ; ; ; ; ;  [2]; ; ;  [3]
  1. Department of Natural History Sciences, Science Faculty, Hokkaido University, Sapporo 060-0810 (Japan)
  2. Institute of Low Temperature Science, Hokkaido University, Sapporo 060–0819 (Japan)
  3. Division of Earth and Planetary Science, Kyoto University, Kyoto 606-8502 (Japan)
Publication Date:
OSTI Identifier:
22661338
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 837; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHONDRITES; DUSTS; ICE; INTERSTELLAR SPACE; IRRADIATION; METEOROIDS; PHYSICAL PROPERTIES; POROUS MATERIALS; PROTOPLANETS; REFRACTORIES; RESIDUES; SOLAR SYSTEM; SPACE; STAR EVOLUTION; ULTRAVIOLET RADIATION

Citation Formats

Piani, L., Tachibana, S., Endo, Y., Sugawara, I., Dessimoulie, L., Yurimoto, H., Hama, T., Tanaka, H., Kimura, Y., Fujita, K., Nakatsubo, S., Fukushi, H., Mori, S., Chigai, T., Kouchi, A., Miyake, A., Matsuno, J., and Tsuchiyama, A., E-mail: laurette@ep.sci.hokudai.ac.jp. Evolution of Morphological and Physical Properties of Laboratory Interstellar Organic Residues with Ultraviolet Irradiation. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA5CA6.
Piani, L., Tachibana, S., Endo, Y., Sugawara, I., Dessimoulie, L., Yurimoto, H., Hama, T., Tanaka, H., Kimura, Y., Fujita, K., Nakatsubo, S., Fukushi, H., Mori, S., Chigai, T., Kouchi, A., Miyake, A., Matsuno, J., & Tsuchiyama, A., E-mail: laurette@ep.sci.hokudai.ac.jp. Evolution of Morphological and Physical Properties of Laboratory Interstellar Organic Residues with Ultraviolet Irradiation. United States. doi:10.3847/1538-4357/AA5CA6.
Piani, L., Tachibana, S., Endo, Y., Sugawara, I., Dessimoulie, L., Yurimoto, H., Hama, T., Tanaka, H., Kimura, Y., Fujita, K., Nakatsubo, S., Fukushi, H., Mori, S., Chigai, T., Kouchi, A., Miyake, A., Matsuno, J., and Tsuchiyama, A., E-mail: laurette@ep.sci.hokudai.ac.jp. Wed . "Evolution of Morphological and Physical Properties of Laboratory Interstellar Organic Residues with Ultraviolet Irradiation". United States. doi:10.3847/1538-4357/AA5CA6.
@article{osti_22661338,
title = {Evolution of Morphological and Physical Properties of Laboratory Interstellar Organic Residues with Ultraviolet Irradiation},
author = {Piani, L. and Tachibana, S. and Endo, Y. and Sugawara, I. and Dessimoulie, L. and Yurimoto, H. and Hama, T. and Tanaka, H. and Kimura, Y. and Fujita, K. and Nakatsubo, S. and Fukushi, H. and Mori, S. and Chigai, T. and Kouchi, A. and Miyake, A. and Matsuno, J. and Tsuchiyama, A., E-mail: laurette@ep.sci.hokudai.ac.jp},
abstractNote = {Refractory organic compounds formed in molecular clouds are among the building blocks of the solar system objects and could be the precursors of organic matter found in primitive meteorites and cometary materials. However, little is known about the evolutionary pathways of molecular cloud organics from dense molecular clouds to planetary systems. In this study, we focus on the evolution of the morphological and viscoelastic properties of molecular cloud refractory organic matter. We found that the organic residue, experimentally synthesized at ∼10 K from UV-irradiated H{sub 2}O-CH{sub 3}OH-NH{sub 3} ice, changed significantly in terms of its nanometer- to micrometer-scale morphology and viscoelastic properties after UV irradiation at room temperature. The dose of this irradiation was equivalent to that experienced after short residence in diffuse clouds (≤10{sup 4} years) or irradiation in outer protoplanetary disks. The irradiated organic residues became highly porous and more rigid and formed amorphous nanospherules. These nanospherules are morphologically similar to organic nanoglobules observed in the least-altered chondrites, chondritic porous interplanetary dust particles, and cometary samples, suggesting that irradiation of refractory organics could be a possible formation pathway for such nanoglobules. The storage modulus (elasticity) of photo-irradiated organic residues is ∼100 MPa irrespective of vibrational frequency, a value that is lower than the storage moduli of minerals and ice. Dust grains coated with such irradiated organics would therefore stick together efficiently, but growth to larger grains might be suppressed due to an increase in aggregate brittleness caused by the strong connections between grains.},
doi = {10.3847/1538-4357/AA5CA6},
journal = {Astrophysical Journal},
number = 1,
volume = 837,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}