Jovian System Data

Cover Page/Proposal Summary

ROSS-99    NRA 99-OSS-01

Date Due: 5/5/99

Objectives: To determine the mechanisms and rates of formation of diffuse, reddish, low albedo features on Europa, including triple band margins and haloes associated with domes and pits, and to understand their implications for liquid water. Two models are proposed: (i) cryovolcanic venting and deposition of material containing some amount of a dark non-ice component; (ii) changes in surface albedo and color due to conductive heating from subsurface (cryomagmatic or diapiric) thermal sources, leading to sublimation and lag deposit formation, or ice grainsize changes. Initial analyses suggest both (i) and (ii) are plausible; our aim is to distinguish with more certainty between intrusive or extrusive origins for these features. Approach: We will use a combination of Galileo data analysis and numerical modeling to assess these and other scenarios, as appropriate. SSI image analysis and detailed mapping will provide information on feature dimensions and constrain the nature of dark features (fluid vs. mantling deposit, etc.), with compositional constraints provided by suitable color or NIMS data. Development of numerical models of cryomagmatic processes will provide information on eruptive/intrusive conditions and timescales required to produce the observed features. Significance: Our work will constrain resurfacing processes and rates, the physical state of Europa?s ice shell, and help resolve the question of the presence, timing and extent of liquid water on Europa, as each model has specific implications for liquid vs. solid state processes. This information will also help distinguish between currently debated ridge-building models. Furthermore, this study will lay groundwork and provide science objectives for future spacecraft missions (e.g., Cassini, Europa Orbiter). Thus, this work is directly relevant to OSS goals of understanding Solar System bodies and seeking habitats conducive to the evolution of life.