They are cooler than the "Medieval Warm Period" about 1, 000 years ago when Eric the Red and his Icelandic Viking tribe settled on grasslands of Greenland's southwestern coast, and much warmer than about 400 years ago when the Northern Hemisphere plunged into depths of a "Little Ice Age" (not a true Ice Age).

FORBES: Would a global warming really be that bad?

Before Mars Global Surveyor, red planet researchers relied on Viking data from the 1970s, which yielded much lower resolution images.

CNN: Scientists debate implications of Mars pictures

Every time they go ashore, the first one says with a severe Viking frown, they must turn their tags on the tag board from green to red.

NEWYORKER: Stone Mattress