5:15 PM - 6:45 PM
[PPS07-P03] Detection of a possible prebiotic molecule Cyanodiacetylene (HC5N) in the middle atmosphere of Titan with ALMA
Keywords:Titan, Astrobiology, ALMA, Planetary Atmosphere
Atmospheric composition of Titan is characterized by the presence of complex nitriles and haze layers.
Nitriles condensed or accreted on haze particle undergo photochemical reactions to form complex polymers, including prebiotic molecules. In particular, photochemical reactions relating to Cyanodiacetylene (HC5N) are important because production of amines and aromatic molecules are expected.
While HC5N is detected in the ionosphere, in the middle and lower atmosphere, where main haze layer is present, previous search obtained only the upper limit abundance. We have carried out a new comprehensive search of HC5N on Titan's atmosphere using 200 GHz band spectroscopic archival data of the Atacama Large millimeter/submillimeter Array (ALMA). Integrating 28 independent observation data, an emission spectrum of HC5N was marginally detected with high accuracy as ~4 sigma. Using radiative transfer analysis, employing the most plausible vertical distribution of slope profile, the column density was derived to be 0.9% of HC3N, the ssimplest cyanopolyyne. The derived abundance ratio was in the intermediate value of ionospheric and stratospheric experimental value.
Since the employed profile locates at the same altitude with main and detached haze layers, the result may lead to the incorporation of HC5N onto haze particle and resulted production of complex molecules.
Nitriles condensed or accreted on haze particle undergo photochemical reactions to form complex polymers, including prebiotic molecules. In particular, photochemical reactions relating to Cyanodiacetylene (HC5N) are important because production of amines and aromatic molecules are expected.
While HC5N is detected in the ionosphere, in the middle and lower atmosphere, where main haze layer is present, previous search obtained only the upper limit abundance. We have carried out a new comprehensive search of HC5N on Titan's atmosphere using 200 GHz band spectroscopic archival data of the Atacama Large millimeter/submillimeter Array (ALMA). Integrating 28 independent observation data, an emission spectrum of HC5N was marginally detected with high accuracy as ~4 sigma. Using radiative transfer analysis, employing the most plausible vertical distribution of slope profile, the column density was derived to be 0.9% of HC3N, the ssimplest cyanopolyyne. The derived abundance ratio was in the intermediate value of ionospheric and stratospheric experimental value.
Since the employed profile locates at the same altitude with main and detached haze layers, the result may lead to the incorporation of HC5N onto haze particle and resulted production of complex molecules.