Low levels of sulphur dioxide contamination of Venusian phosphine spectra

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 and Fraser, Helen J (2022). Low levels of sulphur dioxide contamination of Venusian phosphine spectra. Monthly Notices of the Royal Astronomical Society, 514(2) pp. 2994–3001.

DOI: https://doi.org/10.1093/mnras/stac1438

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 June 2017, 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 ≲2.5 per cent (for the least-noisy half of the planetary disc). The contamination-subtracted ALMA and JCMT spectra (of 6-8 sigma confidence) are now consistent with similar absorption-depths at the two epochs. The two values span -1.7(±0.5) 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.

Viewing alternatives

Metrics

Item Actions

Export

You can export this page using these formats Digital Object Identifier - DOI