Viking 1 and 2, both of which landed in 1976, returned the first useable data from the planet's surface, as well as providing further mapping from their respective orbiters. The image shows Ascraeus ... more 
Viking 1 and 2, both of which landed in 1976, returned the first useable data from the planet's surface, as well as providing further mapping from their respective orbiters. The image shows Ascraeus Mons, an extinct volcano more than twice as h less 
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SPACE.com | Photo By UCL Faculty of Mathematical and Physical Sciences
Mon, Nov 18, 2013 10:05 AM EST