photos credit NASA from current Cassini mission         Above:  radar images of Titan’s dunes   Below:  photos of South Africa’s Nambian Desert

reported by Discovery News  February 20, 2012

Titan’s surface temperature is minus 300 degrees Fahrenheit, hardly the  climate we associate with Earth’s dunes.  Nor is the composite material of the dunes what we’re accustomed to on our planet.

Titan’s dunes aren’t made of sand.  When the sun’s ultraviolet light breaks apart methane high in Titan’s atmosphere, the result is ethane and hydrogen.  As these chemicals coalesce into particles, they settle out and fall as tar-like grains of hydrocarbon, the size of coarse sand.

The southern hemisphere of Saturn’s most famous moon is dry with short, intense summers because of Saturn’s slightly elliptical orbit. The resulting arid sand is carried northward by winds to form extensive dunes along an equatorial belt.

Titan’s gravity is weak, slightly less than that of our own moon.  Consequently, the dunes stand over 300’ high, stretch a mile across and cover an area the size of the United States.  In contrast, Mars’s dune fields cover only the planet’s far northern latitudes.  Venus has only a few dunes, probably because of the lack of strong surface winds and sand particles.

Because of Titan’s unusual topography, engineers are considering robotic explorers to investigate its volcanoes and methane seas and lakes.  One design, the TALE (Titan Airship Latitude Excursion), is a nuclear–powered buoyant-gas ship with sufficient power to travel at different latitudes, surveying the landscape from polar lakes to equatorial dunes.

Other engineers believe the best way to navigate Titan’s nitrogen-dense atmosphere is with a heavier-than-air, nuclear-powered, small-winged drone called Aviatr.  After taking 3D photos of the moon’s surface, the 260-pound aircraft would attempt a landing on the dunes.

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