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SP-425 The Martian Landscape


[75] Viking 2 Lander Pictures



[76 - 77] Another First


Figure 80


Figure 81

Figure 80 is the first picture taken by Viking 2 Lander. The preprogrammed picture sequence for the first several days was nearly identical to that stored in the Lander 1 computers (fig. 19); to that extent, certain aspects of the Viking 1 and 2 pictures are similar. Note, for example, the vertical streaking at the left side of figure 80. In general, this is very similar to the streaking in the first Viking Lander 1 picture. It occurs in none of the more than 3000 other pictures taken throughout the mission, including a later view of the same area (fig. 81). This evidence conclusively demonstrates that the streaking is the result of a singular event-raising of a dust cloud at the time of touchdown. The detailed configuration of streaking at the two landing sites is different, indicating slightly different dissipation of the dust. At the Lander 1 site the atmosphere was clear after 1 1/2 min. At the Lander 2 site the dust settled more rapidly; clearing was complete within one min.

We had expected (hoped?) that the second landing site would be relatively free of blocks. This first picture made our predictions look a little shaky. The sponge-like rock in the right half of figure 80 provides a dramatic example of vesicular texture. The subspherical cavities probably formed around small gas bubbles in cooling volcanic lava.