JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY



ROSS-98   NRA 98-OSS-05 Confirmation #: 99-070
Date Received:  Jun 19, 1998

Proposal Summary

Objectives: This 2 year study will focus on two main themes. The first is a better understanding of the formation of Iošs large mountains and their relationship to volcanic resurfacing. We will (Task 1) map the morphology, dimensions and heights of Iošs mountains using Voyager and Galileo images and evaluate models for their formation. The second theme is the role of impact cratering in understanding the nature of lithospheres on the icy Galilean satellites and in assessing the impactor population in the jovian system as a means of constraining surface ages. This theme is divided into 3 distinct but related tasks. Task (2) will complete the global inventory of large (>60 km) impact craters on Europa, Ganymede and Callisto, including the geologic mapping, unit correlation, and modelling to assess the role of lithospheric properties in controlling differences in crater morphology on these satellites. Task (3) will be the mapping of crater chains (catena) formed by disrupted comets, which provide a unique sample of the primary impactor flux in the jovian system. Task (4) will be examine both the large crater population on Ganymede and Callisto (using data from Task 2) and the small crater population on Europa as a means of constraining the surface ages of these bodies. Tasks 2-4 are thus directly related to assessing the possible current presence of a sub-crustal ocean on Europa. Significance to NASA OSS Interests: Mapping and measuring of Iošs mountains, some of which exceed 10 km height will improve our understanding of volcanic and tectonic processes on the volcanically active satellite Io and the mechanisms of volcanic resurfacing. These results will provide important constraints for the interpretation of targeted high-resolution GEM images of Io anticipated for late 1999. Our investigations of large impact craters on the icy Galilean satellites are an important means of probing the shallow interiors of these bodies. Geologic comparisons and modleling of the differnces between impact features on Ganymede and Callisto and those on Europa will address important issues regarding the state of the interior of Europa and the ages of these surfaces. These studies may support indications of a youthful surface and a sub-crustal liquid ocean on Europa, one of the quests identified in the "Solar System Roadmap."