europa - Europa and Ganymede Radius: Distance from Jupiters...

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Europa and Ganymede Radius: 1,565 km 2,634 km Distance from 8.5 RJ 14.1 RJ Jupiter’s surface Bulk density 3.0 g/cm 3 1.9 g/cm 3 Albedo 58 % 48% Earth’s moon radius = 1,738 km; hence, Europa is similar in size to our moon, whereas Ganymede is significantly larger, and even larger than Mercury, a planet (r = 2,440 km). RJ = Jupiter’s equatorial radius (71,492 km). Europa’s density, in particular, is quite high; hence, Europa must have a significant amount of internal silicate/metal material, and Ganymede some The albedos of both are high, esp. Europa; hence, consistent with water ice surfaces. SHAPE: Very well defined sphere – one of the smoothest (i.e. lowest topographic relief) objects in the whole solar system. maximum relief is only ~200 m – this alone is interesting because it suggests that either no process generated topography, and/or that topography, if generated, was either smoothed down/over and/or could not be sustained.
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Voyager’s View of Europa
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Surface Features Principal categories (4) of surface feature: (1) Bright plains (2) Mottled terrains (3) Linear Features (4) Craters N.B. We will build the case for a global liquid water ocean below a water ice crust by observation, and then look at key recent geophysical testing data. The water ice crust appears to be ~ 6 – 15 km thick in general, but in local areas may have been thinned down. We will then look at how deep this global Europa ocean may be, because it is possible that it may contain more liquid water than our entire ocean system on earth. Bright plains: These appear to be the oldest terrains, but not at all old (i.e. Young, Indicating resurfacing) in solar system time. Relatively smooth, water ice plains with some topographically higher “Plateaus” up to ~10 km across and 10’s of metres high, and especially patterns of smoothed ridges.
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Trailing Hemisphere of Europa
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Surface Features
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Surface Features: Bright Plains
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Spectral Signatures of Surface Features
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Surface Features –Chaos Regions Mottled terrains: PATCHES ~50 -- >500 KM ACROSS WHICH (a) CONTAIN SO CALLED “chaos” areas, (b) can contain domes with medial fractures and neighbouring lower regions, and (c) which tend to have a distinct dark reddish brown colouring. The “chaos” areas are the most amazing because they contain plates which look like ice-crust fragments which have been generated by fracturing and which have then rafted away from each other for varying distances with the intervening space filled with lower topography ice. In other words, they look very like large icebergs, and their topographic relief relative to the intervening material is up to ~200 metres in one area (conamara chaos; greeley[1999], p.256). hence, since the “below:above” water level ratio for icebergs is ~9:1, the ice crust was, or became, at least 2 km thick in this particular area. The impression of plates floating in a partially liquid sub-layer is reinforced by the
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europa - Europa and Ganymede Radius: Distance from Jupiters...

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