Abstract
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 spectral artefacts arose mainly
from inessential calibration-load signals. By-passing these signals
allows simpler post-processing, and 6.5σ detection of 1 ppb of
PH3 at ~75 km altitude (just above the
clouds). Compiling six phosphine results would suggest the abundance
inverts: 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), as it does
on Earth. Low values/limits were found where the viewed part of the
super-rotating Venusian atmosphere had passed through sunlight, while
the high values are from views moving into sunlight. We suggest Venusian
phosphine is indeed present, and so merits further work on models of its
origins.
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