Low levels of sulphur dioxide contamination of Venusian phosphine spectra

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 percent (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 -1.9(+/-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.

v3 is an proofread version of the paper that will appear in print in MNRAS

References in corpus (13)

• Phosphine Gas in the Cloud Decks of Venus
• The Venusian Lower Atmosphere Haze as a Depot for Desiccated Microbial Life: A Proposed Life Cycle for Persistence of the Venusian Aerial Biosphere
• No evidence of phosphine in the atmosphere of Venus by independent analyses
• Phosphine on Venus Cannot be Explained by Conventional Processes
• Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine
• Claimed detection of PH${}_3$ in the clouds of Venus is consistent with mesospheric SO${}_2$
• Production of Ammonia Makes Venusian Clouds Habitable and Explains Observed Cloud-Level Chemical Anomalies
• The statistical reliability of 267 GHz JCMT observations of Venus: No significant evidence for phosphine absorption
• Complications in the ALMA Detection of Phosphine at Venus
• Recovery of Spectra of Phosphine in Venus' Clouds
• Re-analysis of Phosphine in Venus' Clouds
• On the Robustness of Phosphine Signatures in Venus' Clouds
• Venusian phosphine: a 'Wow!' signal in chemistry?

Cited by in corpus (7)

• Phosphine in the Venusian Atmosphere: A Strict Upper Limit from SOFIA GREAT Observations
• Venus' Atmospheric Chemistry and Cloud Characteristics Are Compatible with Venusian Life
• Astrobiological Potential of Venus Atmosphere Chemical Anomalies and Other Unexplained Cloud Properties
• Constraints on the production of phosphine by Venusian volcanoes
• Recovering Phosphine in Venus' Atmosphere from SOFIA Observations
• Limits to dynamic range in GHz-THz single-dish planetary spectra
• Necessary Conditions for Earthly Life Floating in the Venusian Atmosphere