[X] My Assistant

[Exploitcorporati...]

During the E15 encounter, Galileo accquired the first segments of two massive hemispheric transects. 15ESREGMAP01, on the antijovian side, covers a large area within the famous G1 false color image showing the intersection of Minos and Udaeus Lineae. Presented here is an approximate natural color version along with a comparison with NASA's beautiful and oft-reproduced false color release from 1998:

15ESREGMAP01 greyscale

Color version

3-panel comparison

Cropped scenes of several features are in the wallpapers directory of the FTP site

[Decepticon]

Does that explain why the lines make a cookie bite mark? They look like half circles attached at each ends.

I'm still at a loss how those are formed!

[vexgizmo]

Does that explain why the lines make a cookie bite mark? They look like half circles attached at each ends.

I'm still at a loss how those are formed!

These are the "cycloidal" features. They are thought to form as a crack propagates at an average rate that matches the changing stress direction due to the diurnal stressing as Europa orbits. This is much easier to visualize than to put into words, so I point you to Greg Hoppa's web page for some words of explanation, and excellent animations:

http://pirlwww.lpl.arizona.edu/~hoppa/science.html


The arrow represents the diurnal stress, which rotates and changes in magnitude as Europa orbits each 3.55 days.

This is the abstract of the Hoppa et al. Science paper which first proposed the idea--this is a strong piece of evidence for a subsurface ocean:

Cycloidal patterns are widely distributed on the surface of Jupiter's moon
Europa. Tensile cracks may have developed such a pattern in response to diurnal
variations in tidal stress in Europa's outer ice shell. When the tensile strength
of the ice is reached, a crack may occur. Propagating cracks would move across
an ever-changing stress field, following a curving path to a place and time where
the tensile stress was insufficient to continue the propagation. A few hours
later, when the stress at the end of the crack again exceeded the strength,
propagation would continue in a new direction. Thus, one arcuate segment of
the cycloidal chain would be produced during each day on Europa. For this model
to work, the tensile strength of Europa's ice crust must be less than 40 kilopascals,
and there must be a thick fluid layer below the ice to allow sufficient
tidal amplitude.