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SP-425 The Martian Landscape


The Distant Horizon


Figure 136

[114-115] This panorama of almost 100°, looking toward the east, is broken into two segments, figures 136 and 137. In figure 136 a sequence of increasingly distant ridges can be identified. In the right half of figure 137 a block studded crest close to the spacecraft obscures the distant horizon. The general slope of the horizon is a consequence of spacecraft tilt, not of any natural gradient in the scene. Indeed, the horizon is almost exactly level, displaying significantly less relief than the distant landscape at the Viking 1 site. By coincidence the farthest horizon appears at the lowest point in the tilted image.

The origin of this gently undulating plain at the Viking 2 site is a matter of conjecture, but a likely possibility is that the Lander is situated on a vast ejecta deposit associated with a 100 km crater, Mie, situated 160 km to the east. Eolian deflation might have stripped much of the fine grained material originally in the ejecta deposit. Unfortunately, no landforms in the Lander camera images are identifiable in Orbiter images.


Figure 137

Figure 138


Figure 139

[116-117] Figures 138, 139, and 140 show horizon ridges photographed at three different times of day. Predictably, change in illumination results in different reflections from the broad slopes. Only by reference to all the available pictures can a viewer gain a true impression of the complex detail in the distance. Figure 138 is purposely printed dark to bring out the relatively light horizon details.

Figure 140