The Namib in southern Africa is one of the world’s foggiest deserts, and fog is the main source of moisture for its western region. When McKay visited in 2012, he learned that the foggy western Namib supported as much microbial life as the eastern part of the desert, where rain provides limited moisture. It’s relevant because there is no rain on Mars, also a desert, but there is fog. Of course, Mars is much colder than the Namib, making the match far from exact.
“This is true of all of the environments I study,” McKay admits. “They have similarities to Mars, but none are perfect analogs. That’s why we study so many different ones.”
Fog’s important role in sustaining microbial life drew McKay to the southern African desert, but the Namib also features some of the world’s tallest sand dunes, rising as high as 1,000 feet. These dunes are linear, or longitudinal, formed when winds blow in two predominant directions, varying seasonally — like the dunes on Titan, Saturn’s largest moon.
Titan’s dunes are gigantic by any standard, covering about 13 percent of the moon’s surface, about 4 million square miles in all. Some stretch for hundreds of miles. Extrapolating from what we know about the Namib’s dunes, Titan’s longitudinal dunes offer clues about its global circulation patterns and might one day be used to predict its weather.