Low levels of sulphur dioxide contamination of Venusian phosphine spectra. Issue 2 (30th May 2022)

• Record Type: Journal Article
• Authors: Greaves, Jane S; Rimmer, Paul B; Richards, Anita M S; Petkowski, Janusz J; Bains, William; Ranjan, Sukrit; Seager, Sara; Clements, David L; Silva, Clara Sousa; Fraser, Helen J
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 514:Issue 2(2022)
• Page Start: 2994
• Page End: 3001
• Publication Date: 2022-05-30
• Subjects: planets and satellites: individual: Venus -- radio lines: planetary systems; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac1438
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: New analysis is presented of the 1.1 mm wavelength absorption lines in Venus' atmosphere that suggested the presence of phosphine. We retrieve a sulphur dioxide observation from the JCMT archive that was simultaneous within a few days of the PH3 1-0 spectrum obtained in 2017 June, and demonstrate via a radiative transfer calculation that contamination of PH3 by SO2 was ≈10 per cent. We also present ALMA 2019 spectra of PH3 1-0 and an SO2 transition acquired simultaneously, and infer that SO2 line-contamination was ≲2 per cent (for the least-noisy half of the planetary disc). The contamination-subtracted ALMA and JCMT spectra (of 6–8σ sigma confidence) are now consistent with similar absorption-depths at the two epochs. The two values span −1.9(±0.2) 10 −4 of the continuum signal (which was re-estimated for ALMA), albeit for differing planetary areas. This suggests that the abundance attributed to phosphine in Venus' atmosphere was broadly similar in 2017 and 2019.