  The potential detection of phosphine in the atmosphere of Venus has reignited
interest in the possibility of life aloft in this environment. If the cloud
decks of Venus are indeed an abode of life, it should reside in the "habitable
zone" between ~ 50-60 km altitude, roughly coincident with the middle cloud
deck, where the temperature and pressure (but not the atmospheric composition)
are similar to conditions at the Earth's surface. We map out a precursor
astrobiological mission to search for such putative lifeforms in situ with
instrument balloons, which could be delivered to Venus via launch opportunities
in 2022-2023. This mission would collect aerosol and dust samples by means of
small balloons floating in the Venusian cloud deck and directly scrutinize
whether they include any apparent biological materials and, if so, their
shapes, sizes, and motility. Our balloon mission would also be equipped with a
miniature mass spectrometer that should permit the detection of complex organic
molecules. The mission is augmented by contextual cameras to search for
macroscopic signatures of life in the Venusian atmospheric habitable zone.
Finally, mass and power constraints permitting, radio interferometric
determinations of the motion of the balloons in Venusian winds, together with
in situ temperature and pressure measurements, will provide valuable insights
into the poorly understood meteorology of the middle cloud region.
