P092-06
Search for phosphine in Venus’ atmosphere using Infrared instruments

Friday, 11 December 2020: 10:50
Virtual
Séverine Robert1,2, Loïc Trompet1, Arnaud Mahieux1,3, Frédéric Schmidt4, Justin Erwin1 and Ann Carine Vandaele1, (1)Royal Belgian Insitute for Space Aeronomy, Brussels, Belgium, (2)Université Catholique de Louvain, Louvain-La-Neuve, Belgium, (3)University of Texas at Austin, Austin, United States, (4)Université Paris-Saclay, Orsay, France
Recorded Presentation
Abstract:
In the light of the recent publication of Greaves et al. (2020) reporting the first detection of phosphine in the Venusian clouds, we decided to explore the SOIR database in search for traces of PH3 in the Infrared range.

The Solar Occultation in the InfraRed (SOIR) instrument onboard the ESA Venus Express spacecraft, an infrared spectrometer sensitive from 2.2 to 4.3 µm, probed the atmosphere of Venus from June 2006 until December 2014. During this time, it performed more than 750 solar occultations of the Venus mesosphere and lower thermosphere, at a spectral resolution of 0.12-0.18 cm-1, the highest on board Venus Express. SOIR gathered information on the atmosphere of Venus by looking at the Sun through Venus' atmosphere as the satellite passed into and out of eclipse. As the light beam probes deeper layers in the atmosphere, two processes reducing the transmittance take place: extinction by aerosols and absorption by trace gases. Measurements were made from the top of the atmosphere (~ 170km altitude) down to the cloud tops (~ 62km). High resolution vertical profiles of the concentration of various elements were retrieved, such as H2O [Chamberlain et al., 2020], CO2 [Mahieux et al., 2015], CO [Vandaele et al., 2015], SO2 [Mahieux et al., 2015], hydrogen halides (HCl, HF) [Mahieux et al., 2015].

Additionally, we investigate the potential to detect this molecule with an infrared spectrometer that would sound the Venus’ atmosphere in nadir viewing. VenSpec-H is part of the payload of the candidate M5 mission EnVision. The ESA selection is expected in June 2021 for a launch in 2032. The scientific objectives of VenSpec-H consist in measuring abundances of molecular species such as H2O, HDO, CO, OCS and SO2, in the troposphere and in the mesosphere of Venus. This would be achieved by measuring the infrared range between 1 and 2.5 microns at a high spectral resolution.

The methodologies we used to derive upper limits of PH3 from the SOIR and VenSpec-H observations will be discussed.

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