Author's Reply to Comment by Greaves et al. on “Phosphine in the Venusian Atmosphere: A Strict Upper Limit From SOFIA GREAT Observations”

Cordiner, M. A.; Wiesemeyer, H.; Villanueva, G. L.; de Pater, I.; Stutzki, J.; Liuzzi, G.; Aladro, R.; Charnley, S. B.; Cosentino, R.; Faggi, S.; Kofman, V.; McGuire, B. A.; Milam, S. N.; Moullet, A.; Nixon, C. A.; Thelen, A. E.

doi:10.1029/2023gl106136

Cited by 3 publications

(3 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Wunderlich et al ( 2023) also assume that the kinetics of reaction that break the phosphorus-oxygen double bond could be modelled with reference to the kinetics of analogous chemistry of the nitrogen-oxygen double bond, a parallel that Bains et al (2021b) has shown is very inaccurate. However Wunderlich et al (2023)'s overall conclusion, that the quantitation of the phosphorus photochemistry in Venus' atmosphere is uncertain by many orders of magnitude, and that more experiments and observations are essential for resolving whether PH 3 can be explained abiotically, is consonant with the conclusions of Bains et al (2021bBains et al ( , 2023 and Omran et al (2021).…”

Section: Photochemistry As a Potential Source Of Phosphinementioning

confidence: 99%

“…This route is only valid if P 4 O 6 actually exists in the atmosphere at the altitude of the clouds, which Bains et al (2021b) and Omran et al (2021) concluded that it did not. The mechanism analysed by Wunderlich et al (2023) assume an efficient net production of PO from P 4 O 6 at rates comparable to the production of methane on modern Earth. They do not suggest a mechanism for this unprecedented chemistry, and indeed thermodynamic calculation suggests that it is extremely unlikely (Bains et al, 2021b).…”

Section: Photochemistry As a Potential Source Of Phosphinementioning

confidence: 99%

“…The original group have responded to these criticisms (Greaves et al, 2021a;Greaves et al, 2021c). A major subsequent observation campaign (the JCMT-Venus campaign, number M22AL006: see JCMT (2023) Clements (2022) has found new mm 10.3389/fspas.2024.1372057 absorption evidence for phosphine in the clouds with high significance, using different data reduction approaches from those that were disputed in the original reports (Greaves, 2023). Further work on far infrared spectroscopy (Greaves et al, 2023) has supported the presence of phosphine in Venus' clouds, although dispute the far infrared spectroscopy interpretation.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Source of phosphine on Venus—An unsolved problem

Bains,

Seager,

Clements

et al. 2024

Front. Astron. Space Sci.

View full text Add to dashboard Cite

The tentative detection of ppb levels of phosphine (PH3) in the clouds of Venus was extremely surprising, as this reduced gas was not expected to be a component of Venus’ oxidized atmosphere. Despite potential confirmation in legacy Pioneer Venus mass spectrometry data, the detection remains controversial. Here we review the potential production of phosphine by gas reactions, surface and sub-surface geochemistry, photochemistry, and other nonequilibrium processes. None of these potential phosphine production pathways is sufficient to explain the presence of phosphine in Venus atmosphere at near the observed abundance. The source of atmospheric PH3 could be unknown geo- or photochemistry, which would imply that the consensus on Venus’ chemistry is significantly incomplete. An even more extreme possibility is that a strictly aerial microbial biosphere produces PH3. The detection of phosphine adds to the complexity of chemical processes in the Venusian environment and motivates better quantitation of the gas phase chemistry of phosphorus species and in situ follow-up sampling missions to Venus.

show abstract

Section: Photochemistry As a Potential Source Of Phosphinementioning

confidence: 99%

Section: Photochemistry As a Potential Source Of Phosphinementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Source of phosphine on Venus—An unsolved problem

Bains,

Seager,

Clements

et al. 2024

Front. Astron. Space Sci.

View full text Add to dashboard Cite

show abstract

Stringent upper limits of minor species at the cloud top of Venus: PH₃, HCN, and NH₃

Encrenaz,

Greathouse,

Giles

et al. 2024

A&A

View full text Add to dashboard Cite

Following several reports announcing the detection or non-detection of minor species above the clouds of Venus, we have searched for other possible signatures of PH$_3$, HCN, and NH$_3$ in the infrared range. Since 2012, we have performed ground-based observations of Venus in the thermal infrared at various wavelengths to monitor the behavior of SO$_2$ and H$_2$O at the cloud top. We have identified spectral intervals where transitions of PH$_3$ (around 955 cm$^ $), HCN (around 747cm$^ $), and NH$_3$ (around 951cm$^ $) are present. From the absence of any feature at these frequencies, we derive, on the disk-integrated spectrum, a 3-sigma upper limit of 3 ppbv for the PH$_3$ mixing ratio, 0.5 ppbv for HCN, and 0.3 ppbv for NH$_3$, assuming that these species have a constant mixing ratio throughout the atmosphere. Maps of the Venus disk recorded at the center position of the lines show that there is no evidence for local detection anywhere over the Venus disk. Our results bring new constraints on the maximum abundance of these species at the cloud top and in the lower mesosphere of Venus.

show abstract

Limits to dynamic range in GHz-THz single-dish planetary spectra

Greaves

2024

RAS Techniques and Instruments

View full text Add to dashboard Cite

When bright solar-system objects are observed by GHz-THz regime telescopes, off-axis signals bounce around locally and re-enter the signal path with a time delay, causing sinusoidal ripples in output spectra. Ripples that are unstable over time are challenging to remove. A typical detection limit for planetary spectral lines is a fraction ∼10−3 of continuum signal, restricting searches for minor atmospheric trace-gases. Modern wideband spectra of Venus demonstrate a plethora of effects, at three example telescopes spanning nearly a factor-of-50 in frequency. Characterisation of instrumental effects as families of pure sine-waves via Fourier-analysis is shown to improve dynamic-range by factors of a few. An example upper limit on sulphuric acid (H2SO4) vapour in Venus’ mesosphere, from fully-automated data-cleaning of a 3.5 GHz band containing 10 line components, goes as deep as the best previously-published limit. The most challenging cases are searches for single lines of width comparable to ripple periods. Traditional polynomial-fitting approaches can be deployed to test for false positives, to demonstrate robustness at a level of zero ”fake lines” in >1000 comparisons. Fourier-based data-cleaning avoids subjectivity and can be fully automated, and synthetic spectra can be injected before processing to test to what degree signals are lost in cleaning. An ideal robustness strategy is mitigation at the data-acquisition stage, e.g. using slow drifts in target-velocity with respect to the telescope to isolate a planetary line from a quasi-static instrumental ripple pattern.

show abstract

Author's Reply to Comment by Greaves et al. on “Phosphine in the Venusian Atmosphere: A Strict Upper Limit From SOFIA GREAT Observations”

Cited by 3 publications

References 18 publications

Source of phosphine on Venus—An unsolved problem

Source of phosphine on Venus—An unsolved problem

Stringent upper limits of minor species at the cloud top of Venus: PH₃, HCN, and NH₃

Limits to dynamic range in GHz-THz single-dish planetary spectra

Contact Info

Product

Resources

About

Author's Reply to Comment by Greaves et al. on “Phosphine in the Venusian Atmosphere: A Strict Upper Limit From SOFIA GREAT Observations”

Cited by 3 publications

References 18 publications

Source of phosphine on Venus—An unsolved problem

Source of phosphine on Venus—An unsolved problem

Stringent upper limits of minor species at the cloud top of Venus: PH3, HCN, and NH3

Limits to dynamic range in GHz-THz single-dish planetary spectra

Contact Info

Product

Resources

About

Stringent upper limits of minor species at the cloud top of Venus: PH₃, HCN, and NH₃