VENUS IN OUR BACKYARD: LABORATORY SIMULATION OF THE SURFACE ENVIRONMENT (Invited Presentation)

Laboratory investigations and in situ exploration of Venus, especially of the deep atmosphere and surface, present challenges that are unique among the solar system’s terrestrial bodies. Although most Earth-like in terms of size and proximity to the sun, Venus’ sulfuric acid clouds and ~93 bar, 465 C average surface conditions represent a truly extreme and inhospitable environment.

The challenges of constructing, operating, and maintaining facilities capable of high-fidelity simulation of this hostile environment are considerable. Structural materials typically used for high pressure conditions require careful matching of thermal expansion between different components in order to avoid stresses and leaks. Common aerospace alloys, chosen for their resistance to corrosion, are no longer fully inert when exposed to the supercritical CO₂ and highly reactive sulfur species of Venus’ atmosphere. Furthermore, diffusive and convective mixing efficiencies within a test vessel must be carefully considered in order to avoid the precipitation of carbon soot due to reduction of CO_2­ by transition metal alloys. Analytical monitoring of the test environment is critical in assuring that the desired chemical composition, as well as nominal temperature and pressure, are maintained within experimental requirements.

Currently, the Glenn Extreme Environment Rig, at NASA’s Glenn Research Center, is the largest and most comprehensive Venus surface environment test facility in the world. Eight independent gas streams can be injected to the test chamber, controlled to the part-per-billion level and verified with in-line gas chromatograph, mass spectrometer, and, soon, embedded species-selective sensors. The challenges listed in the preceding paragraph are addressed through specific operation practices, high-frequency environmental monitoring, and the unique ability to replenish and adjust gas compositions throughout a test.

Venus simulation apparatus are crucial for investigating the processes that have shaped and continue to shape Venus today. They provide information on the physical and chemical processes that can occur in the atmosphere, surface, and subsurface of Venus. The data obtained from these experiments will provide context for the information that will be acquired by the upcoming Venus missions.