Editing Viking 2 (section)

===Viking program===

The Viking Orbiters led to significant discoveries about the presence of water on Mars. Huge river valleys were found in many areas. They showed that water floods carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. In the southern hemisphere, the presence of branched stream areas suggests that there was once rainfall.<ref>{{Cite book|isbn = 978-0-8165-1257-7|title = Mars: Maps|last1 = Kieffer|first1 = Hugh H.|date = October 1992|url-access = registration|url = https://archive.org/details/mars0000unse}}</ref><ref>Raeburn, P.  1998.  Uncovering the Secrets of the Red Planet Mars.  National Geographic Society.  Washington D.C.</ref><ref>Moore, P. et al.  1990. ''The Atlas of the Solar System''. Mitchell Beazley Publishers NY, NY.</ref>

The images below are mosaics of many small, high-resolution images.

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Image:Streamlined_Islands_in_Maja_Valles.jpg|Streamlined islands seen by Viking showed that large floods occurred on Mars.  Image is located in [[Lunae Palus quadrangle]].
Image:Viking Teardrop Islands.jpg|Tear-drop shaped islands caused by flood waters from [[Maja Valles]], as seen by Viking Orbiter.  Image is located in [[Oxia Palus quadrangle]].  The islands are formed in the ejecta of [[Lod (crater)|Lod]], [[Bok (Martian crater)|Bok]], and [[Gold (crater)|Gold]] craters.
Image:Chryse Planitia Scour Patterns.jpg|Scour patterns, located in [[Lunae Palus quadrangle]], were produced by flowing water from Maja Valles, which lies just to the left of this mosaic.  Detail of flow around [[Dromore (crater)|Dromore]] crater is shown on the next image.
Image:Detail of Maja Valles Flow.jpg|Great amounts of water were required to carry out the erosion shown in this Viking image.  Image is located in [[Lunae Palus quadrangle]].  The erosion shaped the ejecta around [[Dromore (crater)|Dromore]].
Image:Vedra,_Maumee,_and_Maja_valles.jpg|Waters from [[Vedra Valles]], [[Maumee Valles]], and Maja Valles flowed from Lunae Planum on the left, to [[Chryse Planitia]] on the right.  Image is located in [[Lunae Palus quadrangle]] and was taken by Viking Orbiter.
Image:Kasei Valles topolabled.JPG|Area around northern Kasei Valles, showing relationships among [[Kasei Valles]], [[Bahram Vallis]], [[Vedra Valles]], [[Maumee Valles]], and [[Maja Valles]].  Map location is in [[Lunae Palus quadrangle]] and includes parts of Lunae Planum and [[Chryse Planitia]].
Image:Flow from Arandas Crater.jpg|The ejecta from [[Arandas (crater)|Arandas]] crater acts like mud.  It moves around small craters (indicated by arrows), instead of just falling down on them.  Craters like this suggest that large amounts of frozen water were melted when the impact crater was produced.  Image is located in [[Mare Acidalium quadrangle]] and was taken by Viking Orbiter.
Image:Alba Patera Channels.jpg|This view of the flank of [[Alba Patera]] shows several channels/troughs.  Some channels are associated with lava flows; others are probably caused by running water.  A large trough or graben turns into a line of collapse pits.  Image is located in [[Arcadia quadrangle]] and was taken by Viking Orbiter.
Image:Branched Channels from Viking.jpg|Branched channels in [[Thaumasia quadrangle]], as seen by Viking Orbiter.  Networks of channels like this are strong evidence for rain on Mars in the past.
Image:Dissected Channels, as seen by Viking.jpg|The branched channels seen by Viking from orbit strongly suggested that it rained on Mars in the past.  Image is located in [[Margaritifer Sinus quadrangle]].
Image:Ravi Vallis.jpg|Ravi Vallis, as seen by Viking Orbiter. [[Ravi Vallis]] was probably formed when catastrophic floods came out of the ground to the right (chaotic terrain).  Image located in [[Margaritifer Sinus quadrangle]].
File:Deimos-viking1.jpg|[[Deimos (moon)|Deimos]], photo taken in 1977.
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