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takyon writes:

Astronomers ponder possible life adrift in Venus' clouds

[...] Neighboring Venus is a hostile world. Heat trapped by its dense atmosphere makes it hot enough on its surface to melt lead. But a series of space probes – launched between 1962 and 1978 – showed that temperatures and pressures at comparable heights in Venus' atmosphere (25 miles or 40 km up) don't preclude the possibility of microbial life. Now an international team of researchers has laid out a case for the atmosphere of Venus as a possible niche for extraterrestrial microbial life.

The paper [open, DOI: 10.1089/ast.2017.1783] [DX] was published online March 30, 2018, in the peer-reviewed journal Astrobiology.

From the abstract:

The lower cloud layer of Venus (47.5–50.5 km) is an exceptional target for exploration due to the favorable conditions for microbial life, including moderate temperatures and pressures (∼60°C and 1 atm), and the presence of micron-sized sulfuric acid aerosols. Nearly a century after the ultraviolet (UV) contrasts of Venus' cloud layer were discovered with Earth-based photographs, the substances and mechanisms responsible for the changes in Venus' contrasts and albedo are still unknown. While current models include sulfur dioxide and iron chloride as the UV absorbers, the temporal and spatial changes in contrasts, and albedo, between 330 and 500 nm, remain to be fully explained. Within this context, we present a discussion regarding the potential for microorganisms to survive in Venus' lower clouds and contribute to the observed bulk spectra. In this article, we provide an overview of relevant Venus observations, compare the spectral and physical properties of Venus' clouds to terrestrial biological materials, review the potential for an iron- and sulfur-centered metabolism in the clouds, discuss conceivable mechanisms of transport from the surface toward a more habitable zone in the clouds, and identify spectral and biological experiments that could measure the habitability of Venus' clouds and terrestrial analogues. Together, our lines of reasoning suggest that particles in Venus' lower clouds contain sufficient mass balance to harbor microorganisms, water, and solutes, and potentially sufficient biomass to be detected by optical methods. As such, the comparisons presented in this article warrant further investigations into the prospect of biosignatures in Venus' clouds.

Original Submission