Falling rain carves gullies and riverbeds, and fills lakes and streams. Strong breezes sculpt big sand dunes. And giant storms dump torrential rains on the tropics.
We're talking not about Earth, but about a world that in many ways is the most Earth-like yet discovered: Titan, the largest moon of Saturn. There's one big difference, though. Titan is so cold that it's not water that falls from its clouds and flows across its surface, but liquid methane.
Titan's atmosphere is thicker than Earth's. It's topped by an orange "smog" of organic compounds that hid Titan's surface until the last few years. In 2005, though, a probe landed on Titan. Its mothership, the Cassini orbiter, carries instruments that peer through the clouds. And today, ground-based telescopes are seeing through the haze as well.
These instruments have revealed a landscape that looks a lot like Earth. It's constantly reshaped by rain, wind, and flowing liquid -- just like the landscape on Earth.
And in 2008, a giant storm popped up above Titan's equator. It covered a million square miles. Compared to Titan's size, that would be like a storm on Earth covering most of North America -- a giant storm for a frigid world.
Look for Saturn leading our own Moon across the sky late tonight. It's well to the upper right of the Moon at first light, and looks like a golden star. The true star Spica is much closer to the Moon's left, completing a beautiful morning tableau.
Script by Damond Benningfield, Copyright 2009
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