Site Name : Utopia Planitia
Type of Site: Lander
Latitude: 47.96∞ N
Longitude: 225.77∞ W
Elevation: -2.2 km above martian datum
Corresponding Map on "The Atlas of Mars": MC-7 NW
Viking Orbiter Images: 807A32
The region is part of the vast plains that cover much of the northern hemisphere. Common characteristics of these plains are polygonal fractures, complex albedo patterns, and craters within raised platforms (pedestal craters0, all of which are found around the Utopia Site, but somewhat muted, as though there were a thin cover masking the more general characteristics of the plains.
The topography of the Utopia Planitia is remarkably flat, with slopes in the near field of less than 1 degree and those on the horizon all less than 2 degrees. Several flat-topped bluffs to the east of the spacecraft may correspond to some of the tongues of debris from Mie crater. Within a few meters of the spacecraft are some interconnected, drift-filled troughs, 1 m across and 10 cm deep. They appear to form a polygonal pattern that mimics the pattern observed on a much larger scale in the orbiter photographs. Their origin is unknown. Four interpretations of these features were made: 1) contraction of lava on cooling, although the lack of identifiable flows at the surface argue against this hypothesis 2) formation by dessication of water-saturated clays exposed at the surface 3) formation by fluvial action 4) formation by ice wedging.
While the blocks at the Viking 1 site show a wide variety of shapes, colors, and textures, those at the Viking 2 site are very similar to one another and are generally subangular, equidimensional, and profusely pitted. The blocks are distributed evenly across the surface, with no bedrock outcrops or large drifts. The combination of these characterisitcs gives the scene a remarkably uniform aspect.
Two main models are presented to explain the origin of this plain. The first is that the strewn field is the residue left after aeolian winnowing of a layer of ejecta from Mie crater. The alternative explanation is that the strewn field is the remnant of a thin lava flow that was also deposited over a former extensive aeolian deposit.
The main change observed at the Viking 2 site in the years after landing was the deposition of a thin veneer of water-ice frost, which lasted for a third of the martian year.
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