HR: 0800h
AN: P31A-0962    [Abstracts]
TI: Origin and Evolution of Castalia Macula, An Anomalous Young Depression on Europa
AU: * Prockter, L
EM: Louise.Prockter@jhuapl.edu
AF: Applied Physics Laboratory, MP3-E178 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Schenk, P
EM: schenk@lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058 United States
AB: The Castalia Macula region on Europa was comprehensively imaged by the Galileo spacecraft on several orbits, at both local and regional resolutions and with different illumination geometries. Using the various data sets in combination allows us to map the geology, topography, and color of this area in greater detail than perhaps any other site on Europa. Castalia Macula consists of unusually dark and reddish material, most of which is confined to a broad topographic depression 350 m deep. This depression is located between two large uplifted domes 900 and 750 m high, to the north and south, respectively. The dome to the north of Castalia Macula has the highest elevation of any features yet studied on Europa. The Castalia Macula dark plains deposit covers a region about 600 km^2,$ forming a heart-shaped feature approximately~30 km in diameter. The preservation of ridges at the bottom of Castalia Macula indicates that the dark material may be less than a few tens of meters thick. However, it must initially have been fluid and deep enough to flood ridged plains and some double ridges in the middle and at the edges of the Castalia depression. It appears that dark material initially filled the depression to a certain depth but most of this material was subsequently removed via drainage, resulting in a dark stain up to the old equipotential surface. A small area of chaos existed before the formation of Castalia Macula and the domes, implying at least two episodes of deformation in this area. Superposition and topographic relationships indicate that the Castalia Macula dark plains deposit predates both the southern and northern domes, and secondary craters show that the Macula was emplaced before the impact that formed the very young crater Pwyll. Although older than Pwyll, it nevertheless appears that Castalia Macula and the domes are comparatively young, on the basis of relative albedo, color, and lack of crosscutting features. Thus Castalia Macula could provide an ideal place to sample material that has recently been erupted from the subsurface, and may have been in communication with Europa's ocean. In addition, the surface of Castalia Macula is relatively smooth and flat compared to the majority of Europa's terrain, and so could be a relatively low-risk place to set down a spacecraft. These factors combine to make Castalia Macula a very attractive site for a future Europa lander.
DE: 5464 Remote sensing
DE: 5475 Tectonics (8149)
DE: 5480 Volcanism (8450)
DE: 6020 Ice
DE: 6218 Jovian satellites
SC: Planetary Sciences [P]
MN: 2004 AGU Fall Meeting