From atmospheric evolution to the search of species of astrobiological interest in the Solar System &#8211; Case-Studies using the Planetary Spectrum Generator
Authors: Dias João , Machado Pedro , Ribeiro José , Freire Constança 
Published: March 2022

&lt;p&gt;We used the Planetary Spectrum Generator (PSG) [1] a radiative transfer suite, with the goal of simulating spectra from observations of Venus, Mars and Jupiter, searching for minor chemical species.&lt;/p&gt;&lt;p&gt;For Venus, sulphur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;) absorption lines were detected and its abundance constrained, by comparing simulations with observations by the Texas Echelon Cross Echelle Spectrograph (TEXES) spectrograph, around 7.4 &amp;#956;m [2]. The mean abundance of SO&lt;sub&gt;2&lt;/sub&gt; was constrained to 120 ppb, using the Optimal Estimation Method [3] and a line-depth ratio method [2] independently, in agreement with 50-175 ppb obtained by Encrenaz et al [2].&amp;#160; Phosphine (PH3) was not detected in the comparison between simulation and TEXES Infrared (IR) observations [4], around 10.5 &amp;#956;m, due to the presence of a strong telluric water band in the spectra.&lt;/p&gt;&lt;p&gt;For Mars, both a positive and a negative detection of methane were reanalyzed using PSG simulations with the goal of constraining the methane abundance. The related spectra observations in the IR, around 3.3 &amp;#956;m, report, respectively, to the Mars Express (MEx) [5] and ExoMars [6] space-probes.&lt;/p&gt;&lt;p&gt;For Jupiter, the detection of ammonia, phosphine, deuterated methane and methane was studied, by comparing simulations with IR observations by the Infrared Space Observatory (ISO), around 7-12 &amp;#956;m. [7]. The next step is focused in the determination of the abundances of the previous species. Independent simulations will be performed using PSG and the NEMESIS state-of-the-art radiative transfer suite [8]&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Funding: &lt;/strong&gt;This research was funded by the Portuguese Fundacao Para a Ciencia e Tecnologia under project P-TUGA Ref. PTDC/FIS-AST/29942/2017 through national funds and by FEDER through COMPETE 2020 (Ref. POCI-01-0145 FEDER-007672).&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Aknowledgments: &lt;/strong&gt;We credit Th&amp;#233;r&amp;#232;se Encrenaz, from LESIA, Observatoire de Paris, for all the support and fruitful discussion; Geronimo Villanueva, from NASA-Goddard Space Flight Center, for discussing issues regarding PSG; Marco Giuranna, PI of the PFS instrument of Mars Express (ESA), Alejandro Cardes&amp;#237;n, from ESAC-ESA, Ann Carine Vandaele, PI of the NOMAD instrument of ExoMars (ESA) and S&amp;#233;verine Robert, from the ExoMars team, for all the support regarding Mars dedicated research; Gabriella Gilli (IAA), for the collaboration regarding the LMD-VGCM model; Patrick Irwin, from the University of Oxford (UK), for the collaboration under the NEMESIS radiative transfer code; Asier Munguira, from the University of the Basque Country, for his availability to discuss atmospheric research methods in the context of the present work.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[1]&lt;/strong&gt; Villanueva et al. 2018,&lt;em&gt; Journal of Quantitative Spectroscopy and Radiative Transfer&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[2]&lt;/strong&gt; Encrenaz et al. 2012; &lt;em&gt;Astronomy &amp; Astrophysics&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[3&lt;/strong&gt;] C. D. Rodgers. Inverse methods for atmospheric sounding: theory and practice. World Scientific, 2008&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[4]&lt;/strong&gt; Encrenaz et al. 2020; &lt;em&gt;Astronomy &amp; Astrophysics&lt;/em&gt;.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[5]&lt;/strong&gt; Giuranna et al. 2019; &lt;em&gt;Nature&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[6]&lt;/strong&gt; Korablev &lt;em&gt;et al. &lt;/em&gt;2019.; &lt;em&gt;Nature&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[7]&lt;/strong&gt; Encrenaz et al. 1999 ; &lt;em&gt;Planetary and Space Science&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[8]&lt;/strong&gt; Irwin et al. 2008 ; &lt;em&gt;Journal Of Quantitative Spectroscopy And Radiative Transfer&lt;/em&gt;&lt;/p&gt;