  In the planetary atmosphere, hydrogen cyanide (HCN) is an important
nitrogen-bearing molecule that plays a key role in the formation of several
biomolecules via chain reactions. The presence of an HCN characterizes the
stratospheric composition of the solar gas planets and exoplanets. For several
years, many observations have failed to detect the 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 J = 4$-$3 transition line of the HCN from the
eastern and western limbs of Saturn with $\geq$5$\sigma$ statistical
significance. The derived abundances of HCN in the western and eastern limbs
were 6.19 ppb and 2.90 ppb, respectively. We claim that HCN was formed in the
atmosphere of Saturn via the photolysis of methane (CH$_{4}$) and ammonia
(NH$_{3}$).
