The search for extraterrestrial life is one of the most exciting frontiers in astronomy, and the recent detection of a potential biosignature in the atmosphere of Venus has now raised the possibility that life might exist on the nearest planet to Earth.  

Absorption of light at millimeter wavelengths by phosphine molecules has been identified in the Venusian cloud deck 35 miles above ground level, where the temperature and pressure are similar to what they are in the lower atmosphere of Earth. There, microbes may reside in droplets at a density that is orders of magnitude smaller than in air on Earth; if so, they could have common ancestry to terrestrial life, given that asteroids occasionally graze the atmospheres of both planets, potentially transferring material from one to the other. Of course, conclusive evidence for Venusian life will have to await a probe that would scoop material from the Venusian clouds and search for microbes within it.

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