Volatiles and Organics: The Stuff of Life

6. What global mechanisms affect the evolution of volatiles on planetary bodies?

The Origin and Evolution of Habitable Worlds

9. Why have the terrestrial planets differed so dramatically in their evolutions?

Processes: How Planetary Systems Work

11. How do the processes that shape the contemporary character of planetary bodies operate and interact?

Science mission objectives for VISE are as follows:

• Determine the composition of Venus’s atmosphere, including trace gas species and light stable isotopes;

• Accurately measure noble gas isotopic abundance in the atmosphere;

• Provide descent, surface, and ascent meteorological data;

• Measure zonal cloud-level winds over several Earth days;

• Obtain near-infrared descent images of the surface from 10-km altitude to the surface;

• Accurately measure elemental abundances and mineralogy of a core from the surface; and

• Evaluate the texture of surface materials to constrain weathering environment.

Atmospheric Science Objectives:

The composition of the lower atmosphere of Venus is unknown. Without this knowledge, comparisons of the factors that affect climate on Earth and on Venus, including photochemistry, clouds, volcanism, surface-atmosphere interactions, and the loss of light gases to space, are impossible. VISE will measure the abundance of trace gas species in the lower atmosphere of Venus to parts per million accuracy, enabling an understanding of how these processes affect terrestrial planetary climates. A fundamental quest is to understand how and why Venus, roughly the same size, composition, and distance from the Sun as Earth, has evolved to such a different state. The record of planetary atmospheres is contained in the isotope ratios of the most inert gases—xenon, krypton, argon, and neon. Are planetary atmospheres the remnants of gases that were originally solar in composition but then suffered massive hydrodynamic escape, or did they require atmospheres from volatiles that had already been differentiated? What was the role of impacts on the ultimate compositions and evolution of the terrestrial planets? Discrimination