  The key goals of the astrobiology community are to identify environments
beyond Earth that may be habitable, and to search for signs of life in those
environments. A fundamental aspect of understanding the limits of habitable
environments and detectable signatures is the study of where such environments
can occur. Thus, the need to study the creation, evolution, and frequency of
environments hostile to habitability is an integral part of the astrobiology
story. The study of these environments provides the opportunity to understand
the bifurcation between habitable and uninhabitable conditions on planetary
bodies. The archetype of such a planet is Earth's sibling planet, Venus, which
provides a unique opportunity to explore the processes that created a
completely uninhabitable environment and thus define the conditions that rule
out bio-related signatures. We advocate a continued comprehensive study of our
neighboring planet, to include models of early atmospheres, compositional
abundances, and Venus-analog frequency analysis from current and future
exoplanet data. Critically, new missions to Venus that provide in-situ data are
necessary to address the major gaps in our current understanding, and to enable
us to take the next steps in characterizing planetary habitability.
