A composite image of Titan.
Saturn's moon Titan puts on quite a show in the latest composite image from NASA. Taken with the Cassini spacecraft, the new image uses near-infrared wavelengths to cut through Titan's thick layers of haze. Beneath, you'll notice, is a shockingly Earth-like moon.
Let's be clear: It's not like Titan is some kind of Earth twin that just happened to jump into orbit around Saturn. But in a solar system full of planets that look nothing like our own, it's uncanny to see something this familiar.
But it just goes to show that you can't judge a book by its cover.
NASA describes Titan as "one of the most Earth-like worlds we have found to date." Its air isn't breathable (it's almost entirely nitrogen, with a little methane thrown in instead of oxygen) and at -290 Fahrenheit, it's way too cold for a human to chill on. But if you had a breathing mask and the best thermal underwear ever created, you could jump around in gravity a bit weaker than our own moon's and see some surprisingly Earth-like features.
Titan is covered in dunes formed by the wind that whips across its surface. Liquid ethane and methane sometimes rain or snow down from the sky, and the same compounds form rivers and lakes. There may even be volcanos that spout liquid water instead of rocky lava. Scientists believe the moon is filled with an ocean made of water and ammonia, and that these ice volcanoes help replenish the moon's atmosphere periodically.
Planetary scientists love finding environments that are similar-to-but-different-from Earth in these ways. We know what happens when a river flows on Earth, but how does that phenomenon change when the river in question is made of methane? Those are the kinds of big, weird questions that places like Titan can help us answer.
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