TY - JOUR
T1 - Organic solids produced from simple C/H/O/N ices by charged particles
T2 - Applications to the outer solar system
AU - Khare, B. N.
AU - Thompson, W. R.
AU - Chyba, C. F.
AU - Arakawa, E. T.
AU - Sagan, C.
N1 - Funding Information:
This research was supported in part by NASA grants NGR 33—010-220 and NGR 33—010-101, and by the Office of Health and Environmental Research, U.S. Dept. of Energy, under contract
PY - 1989
Y1 - 1989
N2 - CH4, CO, and CO2 are all potential one-carbon molecular repositories in primitive icy objects. These molecules are all found in the Comet Halley coma, and are probable but, (except for CH4 detected on Triton and Pluto) undetected subsurface constituents in icy outer solar system objects. We have investigated the effects of charged particle irradiation by cold plasma discharge upon surfaces of H2O:CH4 clathrate having a 200:1 ratio, as well as upon ices composed of H2O plus C2H6 or C2H2 (sometimes plus NH3) which are also plausible constituents. These materials color and darken noticeably after a dose 109-1010 erg cm-2, which is deposited rapidly (≤ 104 yr.) in solar system environments. The chromophore is a yellowish to tan organic material (a tholin) which we have studied by UV-VIS reflection and transmission, and IR transmission spectroscopy. Its yield, -1 C keV-1, implies substantial production of organic solids by the action of cosmic rays and radionuclides in cometary crusts and interiors, as well as rapid production in satellite surfaces. This material shows alkane bands which Chyba and Sagan have shown to well match the Halley infrared emission spectrum near 3.4 μm, and also bands due to aldehyde, alcohol and perhaps alkene/aromatic functional groups. We compare the IR spectral properties of these tholins with the spectra of others produced by irradiation of gases and ices containing simple hydrocarbons.
AB - CH4, CO, and CO2 are all potential one-carbon molecular repositories in primitive icy objects. These molecules are all found in the Comet Halley coma, and are probable but, (except for CH4 detected on Triton and Pluto) undetected subsurface constituents in icy outer solar system objects. We have investigated the effects of charged particle irradiation by cold plasma discharge upon surfaces of H2O:CH4 clathrate having a 200:1 ratio, as well as upon ices composed of H2O plus C2H6 or C2H2 (sometimes plus NH3) which are also plausible constituents. These materials color and darken noticeably after a dose 109-1010 erg cm-2, which is deposited rapidly (≤ 104 yr.) in solar system environments. The chromophore is a yellowish to tan organic material (a tholin) which we have studied by UV-VIS reflection and transmission, and IR transmission spectroscopy. Its yield, -1 C keV-1, implies substantial production of organic solids by the action of cosmic rays and radionuclides in cometary crusts and interiors, as well as rapid production in satellite surfaces. This material shows alkane bands which Chyba and Sagan have shown to well match the Halley infrared emission spectrum near 3.4 μm, and also bands due to aldehyde, alcohol and perhaps alkene/aromatic functional groups. We compare the IR spectral properties of these tholins with the spectra of others produced by irradiation of gases and ices containing simple hydrocarbons.
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U2 - 10.1016/0273-1177(89)90362-1
DO - 10.1016/0273-1177(89)90362-1
M3 - Article
C2 - 11537360
AN - SCOPUS:0024959144
SN - 0273-1177
VL - 9
SP - 41
EP - 53
JO - Advances in Space Research
JF - Advances in Space Research
IS - 2
ER -