Moons
Moons

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Moons

3.2.10 Identify features on Europa for yourself

Now explore these surface features of Europa.

Activity 2

Figure 34 Age relationships.

This is a 20-km wide image of part of Europa where the surface is made of ‘ball-of-string’ terrain. Which region do you think is older: the bright region or the dark ‘ball-of-string’ region?

Answer

Figure 35

The brighter band (1) is younger than the darker ‘ball-of string’ textured area. It cuts across the darker area (2), showing that it must have formed later.

Figure 36 Domes

This is an 80-km wide region of Europa. It is mostly ‘ball-of-string’ terrain, but this has been warped or disrupted by doming from below. Most domes are 5–10 km across. See if you can identify some domes, and then see what we found.

Answer

Figure 37

We have pinpointed the three most prominent domes in this image, but there are more.

Figure 38 Offset ridge.

This is a 15-km wide image of ‘ball-of-string’ terrain in Europa. There is one place where a ridge with a central groove has been offset by sideways slip along a fault. Try to find this, and estimate the amount of offset before you click to reveal the annotated version.

Answer

Figure 39

A ridge has been offset in the centre of the circle. This suggests lateral movement. Given that the image is 15 km wide, the offset is about 0.8 km.

Figure 40 Raft features.

This image, roughly 34 km by 42 km, is part of a ‘chaos’ region consisting of rafts of ice that have broken apart and drifted into new positions before the slushy matrix between the rafts refroze. See if you can distinguish between rafts (still bearing ‘ball-of string’ texture) and matrix (representing the refrozen exposed ocean that was temporarily exposed as the rafts drifted apart), before you click to reveal the annotated version.

Answer

Figure 41

We have outlined the largest raft (which has neighbours close by to which it could be refitted without too much movement) and circled two other rafts that are more isolated. There are plenty of other rafts in this image. Shadows show that their surface is 100–200 m above the matrix. The matrix is a jumbled mess, lacking ‘ball-of-string’ texture, although there is a groove running through the matrix diagonally from the lower right corner that must have formed after the matrix refroze. Eventually, after many more grooves have formed, the matrix may become indistinguishable from ‘ball-of-string’ terrain.

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