Unravelling the mysteries of Venusian atmospheric evolution through future orbital space physics measurements

Abstract:

Without a dipole magnetic field at Venus, the solar wind directly interacts with the ionosphere, and its atmosphere is lost to space in a comet-like tail. Today Venus is exceptionally dry, although there is evidence that Venus was once much wetter and may once have been habitable. The harsh conditions on the planet’s surface today severely limits the feasibility, scope, and longevity of in-situ investigations there, yet the upper atmosphere, ionosphere, and magnetosphere are accessible. Thus, substantial advances in understanding the evolution of Venus could be made from orbit. While these regions have been explored by NASA’s Pioneer Venus Orbiter and ESA’s Venus Express, obstacles such as orbital bias and instrument resolution have left several major questions about atmospheric dynamic and escape unanswered. We collectively advocate for future space physics investigations at Venus to 1.) Understand the physical processes and external drivers that facilitate Venusian atmospheric escape to space, so that we may extrapolate the state of the atmosphere backwards through time. 2.) Explore ancient Venus through measurements of the escape rates and enrichment of key species such as Deuterium, Noble elements, and Nitrogen; 3.) Provide a crucial point of comparison to similar escape processes Earth and Mars, enabling an accurate understanding of the importance of intrinsic magnetic fields and gravity in retaining planetary atmospheres, informing our understanding of the evolution of planetary habitability in the solar system and beyond; and finally 4) Monitor space weather and solar transient activity at 0.7 AU. A mission capable of enabling these goals is conceivable with existing (or near-future) technology and would constitute a low-cost key component in the future exploration of Venus’ atmosphere.