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  • 1
    Publication Date: 2019-07-13
    Description: We present spectral and spatial information for major volatile species in Comet 10P/Tempel 2, based on high-dispersion infrared spectra acquired on UT 2010 July 26 (heliocentric distance Rh = 1.44 AU) and September 18 (Rh = 1.62 AU), following the comet's perihelion passage on UT 2010 July 04. The total production rate for water on July 26 was (1.90 +/- 0.12) x 10(exp 28) molecules per sec, and abundances of six trace gases (relative to water) were: CH3OH (1.58% +/- 0.23%), C2H6 (0.39% +/- 0.04%), NH3 (0.83% +/- 0.20%), and HCN (0.13% +/- 0.02%). A detailed analysis of intensities for water emission lines provided a rotational temperature of 35 +/- 3 K. The mean OPR is consistent with nuclear spin populations in statistical equilibrium (OPR = 3.01 +/- 0.18), and the (1(sigma)) lower bound corresponds to a spin temperature greater than 38 K. Our measurements were contemporaneous with a jet-like feature observed at optical wavelengths. The spatial profiles of four primary volatiles display strong enhancements in the jet direction, which favors release from a localized vent on the nucleus. The measured IR continuum is much more sharply peaked and is consistent with a dominant contribution from the nucleus itself. The peak intensities for H2O, CH3OH, and C2H6 are offset by approx. 200 km in the jet direction, suggesting the possible existence of a distributed source, such as the release of icy grains that subsequently sublimed in the coma. On UT September 18, no obvious emission lines were present in our spectra, nevertheless we obtained a 3(sigma) upper limit Q(H2O) less than 2.86 x 10(exp 27) molecules per sec.
    Keywords: Exobiology
    Type: GSFC-E-DAA-TN8865 , Icarus (ISSN 0019-1035); 218; 1; 644-653
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: Comets retain relatively primitive icy material remaining from the epoch of Solar System formation, however the extent to which their ices are modified remains a key question in cometary science. One way to address this is to measure the relative abundances of primary (parent) volatiles in comets (i.e., those ices native to the nucleus). High-resolution (lambda/delta lambda greater than 10(exp 4)) infrared spectroscopy is a powerful tool for measuring parent volatiles in comets through their vibrational emissions in the approximately 3-5 micrometer region. With modern instrumentation on world-class telescopes, we can quantify a multitude of species (e.g., H2O, C2H2, CH4, C2H6, CO, H2CO, CH3OH, HCN, NH3), even in comets with modest gas production. In space environments, compounds of keen interest to astrobiology could originate from HCN and NH3 (leading to amino acids), H2CO (leading to sugars), or C2H6, and CH4 (suggested precursors of ethyl- and methylamine). Measuring the abundances of these precursor molecules and their variability among comets contributes to understanding the synthesis of the more complex prebiotic compounds.
    Keywords: Exobiology
    Type: GSFC.ABS.01080.2012 , Astrobiology Science Conference 2012; Apr 16, 2012 - Apr 20, 2012; Atlanta, GA; United States
    Format: application/pdf
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