Comment on “Phosphine in the Venusian Atmosphere: A Strict Upper Limit
from SOFIA GREAT Observations” by Cordiner et al.
Searches for phosphine in Venus’ atmosphere have sparked a debate.
Cordiner et al. 2022 analyse spectra from the Stratospheric Observatory
For Infrared Astronomy (SOFIA) and infer <0.8 ppb of PH3. We
noticed that some spectral artefacts arose from non-essential
calibration-load signals. By-passing these signals allows simpler
post-processing and a 5.7σ candidate detection, suggesting
~3 ppb of PH3 above the clouds. Compiling six phosphine
results hints at an inverted abundance trend: decreasing above the
clouds but rising again in the mesosphere from some unexplained source.
However, no such extra source is needed if phosphine is undergoing
destruction by sunlight (photolysis), to a similar degree as on Earth.
Low phosphine values/limits are found where the viewed part of the
super-rotating Venusian atmosphere had passed through sunlight, while
high values are from views moving into sunlight. We suggest Venusian
phosphine is indeed present, and so merits further work on models of its