The committee concluded that several of the goals of NASA’s Venus Exploration Analysis Group (VEXAG) should be included with the goals established in the decadal survey, particularly those concerning understanding the thermal balance of the atmosphere of Venus and gathering global mineralogic data.
The New Frontiers announcement of opportunity should not exclude a Venus In Situ Explorer (VISE) mission that addresses the major goals for chemical sampling of Venus’s mid- to lower atmosphere and for characterizing atmospheric dynamics but that lacks a surface sampling component.
The science goals for a VISE mission, which are not in priority order, should be as follows:
Understand the physics and chemistry of Venus’s atmosphere through measurement of its composition, especially the abundances of sulfur, trace gases, light stable isotopes, and noble-gas isotopes;
Constrain the coupling of thermochemical, photochemical, and dynamical processes in Venus’s atmosphere and between the surface and atmosphere to understand radiative balance, climate, dynamics, and chemical cycles;
Understand the physics and chemistry of Venus’s crust, for example through analysis of near-infrared descent images from below the clouds to the surface and through measurements of elemental abundances and mineralogy from a surface sample;
Understand the properties of Venus’s atmosphere down to the surface through meteorological measurements and improve understanding of Venus’s zonal cloud-level winds through temporal measurements over several Earth days;
Understand the weathering environment of the crust of Venus in the context of the dynamics of the atmosphere of Venus and the composition and texture of its surface materials; and
Map the mineralogy and chemical composition of Venus’s surface on the planetary scale for evidence of past hydrological cycles, oceans, and life and constraints on the evolution of Venus’s atmosphere.
The Comet Surface Sample Return mission candidate should seek to answer the following science questions as they were originally stated in the decadal survey (not in priority order),1 although not all of them must be answered with a single mission.
What is the elemental, isotopic, organic, and mineralogical composition of cometary materials?
How is cometary activity driven?
How do small bodies accrete?
What are the scales of physical and compositional heterogeneity?
How are the particles on a cometary nucleus bound together?
What are the macroscopic mineralogical and crystalline structure and isotopic ratios in cometary solids?
The committee further recommends that the New Frontiers announcement of opportunity should leave the choice of target comet to the proposer; the choice of target should be a major factor for evaluation.
The committee recommends that a Network Science mission be included in the forthcoming NASA New Frontiers announcement of opportunity. The decadal survey identified a network science mission’s primary objective as geophysics. For Mars, atmospheric measurements near the surface are a valuable supplement to the geophysics measurements but cannot be a substitute for them.