Phosphine on Venus Cannot Be Explained by Conventional Processes

Area of Science:

• Astrobiology
• Planetary Science
• Atmospheric Chemistry

Background:

• Recent candidate detection of phosphine (PH3) in Venus's atmosphere at ~1 ppb.
• Phosphorus-containing species have not been previously modeled for Venus.
• The origin of atmospheric phosphine on Venus is currently unexplained.

Purpose of the Study:

• To investigate potential formation pathways for phosphine in the Venusian environment.
• To assess known chemical and geochemical processes as sources of Venusian phosphine.
• To evaluate phosphine as a potential biosignature on Venus.

Main Methods:

• Modeling of phosphorus-containing species in Venus's atmosphere.
• Exploration of gas-phase reactions, photochemistry, and geochemical reactions.
• Investigation of potential phosphine formation in the atmosphere, clouds, haze, surface, and subsurface.

Main Results:

• No known geochemical or photochemical pathways adequately explain the observed ppb levels of phosphine.
• Existing models of Venusian atmospheric chemistry are insufficient to account for the phosphine detection.
• The presence of phosphine suggests unknown processes may be occurring on Venus.

Conclusions:

• If confirmed, Venusian phosphine likely originates from unknown geochemistry, photochemistry, or biological activity.
• Phosphine on Venus could represent a biosignature, warranting further investigation.
• The findings emphasize the need for in situ missions to Venus for sample analysis and atmospheric characterization.