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[161] Landing sites for the Viking landers were chosen before launch, but close inspection from orbit showed them to be much too rugged and dangerous to risk landing on.


Viking Orbiter 1 searched for almost 3 weeks before finding a new, more suitable landing site about 800 km west-northwest of the original site, but still within Chryse Planitia. Because of the unexpected search for a new landing site, the original goal of landing on the historic date of July 4, 1976 was lost; the landing was achieved instead on July 20.


Viking Orbiter 1 took pictures of the proposed landing site for the second lander; from these it was determined, even before the second spacecraft arrived at Mars, that the site was not acceptable. Almost half of the planet's surface between 40° and 50° N was photographed in the attempt to find a suitable landing site for the second lander. Finally a site found in Utopia Planitia, and the second successful was made on September 3, 1976.




Chryse Planitia. This map is constructed from a series of images acquired d by Viking (Orbiter 1 on revolutions 10, 20, and 22. Chryse Planitia is an area of plains that seems Ins to be volcanic in origin. The surface is characterized by mare-like ridges and relatively young impact craters, although subdued or part-filled craters are also present. At the left is a higher region of cratered terrain in which arc several large channels. [USGS map M1M 23/50 CMC , 1977: I-1068]



High Resolution Mosaic of the Viking Lander I Site. The periapsis of Viking Orbiter 2 was lowered to 300 km to obtain high resolution images of the surface. The images here were taken by the spacecraft on revolution 452, and craters as small as 30 meters across can be seen. Craters A, B, C, and D are the same craters as shown in the map of the Yorktown region. Rims of craters (' and E can be seen in images taken on the surface by Viking Lander 1. [452B09-11]

Yorktown Region of Chryse Planitia. This map shows Yorktown Crater-an 8-km diameter young impact crater at the top left. Several branches of the Xanthe Dorsa mare-like ridge system are also shown. The major craters on this map have been tentatively assigned names to commemorate the 13 American colonies and the ports and countries with which they traded. 'The craters labeled A, B, C, and D are also shown in the mosaic below. [USGS map M250K 22/48 CMC, 1977; I-1059]





Panorama of Landscape. This view of part of the horizon around Viking Lander 1 was taken shortly after landing. At the left, about 100 meters away, is the northwest portion of the rim of crater E in the high resolution mosaic on the previous page. At the right is the rim of (crater C, about 1.8 km away. The slight depression in the foreground just to the right of center may be a shallow, 3-meter-diameter secondary impact crater. [Viking Lander I Camera Event 12A002]




Mosaic of the Canberra region. This mosaic, an enlargement of part of the mosaic of the Utopia Planitia region on the previous page, shows the detail around the site of Viking Lander 2. Most of the craters in this region are the pedestal type, produced when wind scoured away softer, more erodable material between craters and left exposed the harder, more resistant material around the crater rims. The larger craters have been tentatively named for launch facilities, tracking stations, and mission control centers used in 1976. [USGS map M250K 48/226 CM, 1977; I-1060]




Panorama of Landscape. This panorama of the terrain surrounding the site of Viking Lander 2 was taken by the spacecraft lander shortly after touchdown. The large number of rocks and boulders was a surprise because prelanding evidence suggested that the area would be covered by a thin (tens of meters) sand sheet. Feature A on the far horizon is believed to be ejecta from the rim of Mie Crater. The large dip in the horizon was caused by the lander being tilted. [Viking Lander 2 Camera Event 22A002]



Mosaic of the Utopia Planitia Region. Viking Orbiter 2 acquired these pictures on revolution 9 during landing, site selection and certification for Viking Lander 2. This part of Utopia Planitia is a polygonally fractured surface covered by a thin layer of presumably windblown material that has preferentially accumulated in the fractures. At the extreme upper right is Mie, a 100-km-diameter impact crater, approximately 200 km east-northeast of the lander. Mie Crater is covered by sand dunes and deflation hollows, both of which are strong evidence of wind activity. To the right of bottom center is Hrad Vallis. [USGS map M1M 46/230 CM, 1977;I-1061]