ALMA | NAOJ | NRAO | ESO | 2020 Feb 14
Planetary scientists using the Atacama Large Millimeter / submillimeter Array (ALMA) revealed the secrets of the atmosphere of Titan, the largest moon of Saturn. The team found a chemical footprint in Titan’s atmosphere indicating that cosmic rays coming from outside the Solar System affect the chemical reactions involved in the formation of nitrogen-bearing organic molecules. This is the first observational confirmation of such processes, and impacts the understanding of the intriguing environment of Titan.
Titan is attracting much interest because of its unique atmosphere with a number of organic molecules that form a pre-biotic environment.
Takahiro Iino, a scientist at the University of Tokyo, and his team used ALMA to reveal the chemical processes in Titan's atmosphere. They found faint but firm signals of acetonitrile (CH3CN) and its rare isotopomer CH3C15N in the ALMA data. ...
There are two important players in the chemical processes of the atmosphere; ultraviolet (UV) light from the Sun and cosmic rays coming from outside the solar system. In the upper atmosphere, UV light selectively destroys nitrogen molecules containing 15N because the UV light with the specific wavelength that interacts with 14N14N is easily absorbed at that altitude. Thus, nitrogen-bearing species produced at that altitude tend to exhibit a high 15N abundance. On the other hand, cosmic rays penetrate deeper and interact with nitrogen molecules containing 14N. As a result, there is a difference in the abundance of molecules with 14N and 15N. The team revealed that acetonitrile in the stratosphere is more abundant in 14N than those of other previously measured nitrogen-bearing molecules. ...
14N/15N Isotopic Ratio in CH3CN of Titan's Atmosphere Measured with ALMA ~ Takahiro Iino, Hideo Sagawa, Takashi Tsukagoshi
- Astrophysical Journal 890(2):95 (20 Feb 2020) DOI: 10.3847/1538-4357/ab66b0
- arXiv.org > astro-ph > arXiv:2001.01484 > 06 Jan 2020 (v1), 07 Jan 2020 (v2)