ALMA detection of hydrogen cyanide in the atmosphere of Saturn

Abstract

In the planetary atmosphere, hydrogen cyanide (HCN) is an important nitrogen (N)-bearing molecule that plays a key role in the formation of several biomolecules via chain reactions. The presence of HCN characterizes the stratospheric composition of the solar gas planets and exoplanets. For several years, many observations have failed to identify the rotational and vibrational emission lines of HCN from the atmosphere of Saturn using ground- and space-based radio telescopes. We present the successful detection of the rotational emission line of HCN from the atmosphere of Saturn using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 7. We detected the \(\textrm{J} = 4\)–3 transition line of the HCN from the eastern and western limbs of Saturn with \({\ge }5\sigma \) statistical significance. The derived abundances of HCN in the western and eastern limbs are 6.19 and 2.90 ppb, respectively. We claim that HCN is formed in the atmosphere of Saturn via the photolysis of methane (\(\hbox {CH}_{4}\)) and ammonia (\(\hbox {NH}_{3}\)).