Phosphine in Venus’ atmosphere: Detection attempts and upper limits above the cloud top assessed from the SOIR/VEx spectra
Loïc Trompet, Séverine Robert, A. Mahieux, Frédéric Schmidt, Justin Erwin, Ann Carine Vandaele
Abstract
Context. Recent detection of phosphine (PH 3 ) was reported from James Clerk Maxwell Telescope and Atacama Large Millimetre/submillimetre Array observations. The presence of PH 3 on Venus cannot be easily explained in the Venus atmosphere and a biogenic source located at or within the clouds was proposed. Aims. We aim to verify if the infrared spectral signature of PH 3 is present in the spectra of Solar Occultation at Infrared (SOIR). If it is not present, we then seek to derive the upper limits of PH 3 from SOIR spectra. Methods. We analyzed the SOIR spectra containing absorption lines of PH 3 . We searched for the presence of PH 3 lines. If we did not find any conclusive PH 3 spectral signatures, we computed the upper limits of PH 3 . Results. We report no detection of PH 3 . Upper limits could be determined for all of the observations, providing strong constraints on the vertical profile of PH 3 above the clouds. Conclusions. The SOIR PH 3 upper limits are almost two orders of magnitude below the announced detection of 20 ppb and provide the lowest known upper limits for PH 3 in the atmosphere of Venus.