Scientists at the University of Washington have proposed a solution to the riddle of where phosphine could have come from on Venus, which was previously considered a potential sign of alien life. According to the findings of the researchers, radio telescopes that recorded unusual molecules in the atmosphere of a neighboring planet, in fact, detected sulfur dioxide. The results of scientific work were accepted for publication in The Astrophysical Journal. This was announced in a press release on Phys.org.
In 2017, using the James Clerk Maxwell Telescope, a group of scientists discovered a feature in the radio emission from Venus at a frequency of 266.94 gigahertz. This frequency corresponds to the absorption of radio waves by phosphine and sulfur dioxide. In 2019, researchers carried out observations of radio emission from Venus at frequencies at which absorption is produced only by sulfur dioxide. They concluded that there is too little sulfur dioxide in the planet's atmosphere to give a powerful signal at 266.94 gigahertz.
In the new study, scientists have modeled conditions in Venus's atmosphere to reproduce signals of phosphine and sulfur dioxide at different levels of the gas envelope. The results show that radio waves were not absorbed in the cloud layer, as previously reported, but 50 kilometers above the surface. At this height, phosphine molecules cannot exist, decaying under the influence of aggressive chemicals and ultraviolet radiation.
It also turned out that previous research grossly underestimated the amount of sulfur dioxide. The reason was the configuration of the ALMA antenna array, due to which the signal was underestimated.
