ALMA detection of sulfur dioxide and carbon monoxide in the atmosphere of Neptune

Abstract

The space and ground-based observations have shown a lot of activities and instabilities in the atmosphere of the giant ice planet Neptune. Using the archival data of high resolution Atacama Large Millimeter/Submillimeter Array (ALMA) with band 7 observation, we present the spectroscopic detection of the rotational emission line of sulfur dioxide (SO$_{2}$) at frequency $\nu$ = 343.476 GHz with transition J=57$_{15,43}$$-$58$_{14,44}$. We also re-detect the emission line of carbon monoxide (CO) at frequency $\nu$ = 345.795 GHz with transition J=3$-$2. The molecular lines of SO$_{2}$ and CO in the atmosphere of Nepure are detected with the $\geq$4$\sigma$ statistical significance. The statistical column density of SO$_{2}$ is N(SO$_{2}$) = 2.61$\times$10$^{15}$ cm$^{-2}$ with rotational temperature $T_{SO_{2}}$ = 50 K and the statistical column density CO is N(CO) = 1.86$\times$10$^{19}$ cm$^{-2}$ with $T_{CO}$ = 29 K. The typical mixing ratio in the atmosphere of Neptune for SO$_{2}$ is 1.24$\times$10$^{-10}$ and CO is 0.88$\times$10$^{-6}$. The SO$_{2}$ and CO gas in the atmosphere of Neptune may create due to Shoemaker-Levy 9 impacts in Jovian planets since 1994.