Life arrives on a moon of Saturn.
Life arrives on a moon of Saturn.
Science, technology, and life.
Jan. 19 2005 1:22 AM

Lords of the Rings

Life arrives on a moon of Saturn.

Life on Titan?
Life on Titan?

You can see the pictures on television or the Internet. One looks like a shoreline photographed from a passing plane. Another looks like a river delta. A third looks like a chain of rocks trickling out toward the center of a shallow lake. It feels as though you could step out and walk across them.

William Saletan William Saletan

Will Saletan writes about politics, science, technology, and other stuff for Slate. He’s the author of Bearing Right.

But you can't walk across them, because they're nearly a billion miles away, on Titan, a moon of Saturn. And because there's almost no oxygen there to breathe. And because the temperature is about 300 degrees below zero.

You can't be there—but you are. You're seeing the pictures through an artificial eye made for humans by humans. The eye belongs to a probe called Huygens, which landed on Titan over the weekend. It took pictures in ultra-freezing temperatures and sent them 40,000 miles through space to a satellite, which relayed them across the solar system to Earth.


To give you some idea of the distance involved, we're about 93 million miles from the sun. Mars is about 140 million miles from the sun. Titan is about 900 million miles from the sun. In basketball terms, the difference between landing a rover on Mars and landing a probe on Titan is the difference between a layup and a full-court heave.

Actually, we didn't send Huygens directly to Titan. We put it on the back of the satellite, Cassini. We made Cassini fly to Saturn. We threaded it through a tiny crack in Saturn's perilous rings. We put Cassini into a perfect orbit around Saturn, passing this moon, then that, then another, taking pictures the whole time. Just before Christmas, Cassini launched Huygens on a 2.5 million-mile trip to Titan. Huygens survived atmospheric entry and opened three parachutes in sequence, ejecting its heat shields and slowing from 12,000 mph to a gentle landing.

Can you imagine that? A machine that can fly a billion miles, sneak through a hole in Saturn's rings, dance around its moons, fire a 700-pound bullseye from a distance of 2.5 million miles, and retrieve pictures from the ground? What could be more amazing?

To that question, there's always an answer. Behind every astonishing creation stands a more astonishing creator. If you can't believe that about the wonders of the universe, maybe you can believe it about the machines now exploring those wonders. Humans discovered new worlds on Earth, but we aren't discovering the new worlds beyond it. We're doing something more radical. We're creating the new discoverers.

We didn't send Cassini straight to Saturn. Given its weight, that was impossible. So we invented a shortcut: We made its route longer. Yes, longer. We sent Cassini around the sun and past Venus for a velocity-boosting "gravity assist" (derived from being slung around the planet) in 1998. Then we sent it around again for two more assists from Venus and Earth in 1999. That gave it enough speed to get to Jupiter for a final gravity assist in 2000, which propelled it to Saturn four years later. The trip required a perfect symphony of projections over seven years, so that Cassini would barely miss each orbiting planet. Total distance: 2.2 billion miles.

So now we have the pictures. They show an orange world of fog, mud, and rocks. They hint at fiords and glaciers. There's liquid on the surface—hydrocarbons, not water—and the remote possibility of life in a warmer layer underground. Scientists wonder whether Titan is "prebiotic"—whether it might have evolved like Earth, had Saturn not been exiled to the far reaches of the solar system. They scour the pictures for signs of life.

But there's already a sign of life on Titan. It's the one thing the camera can't show you: itself. Atop the orange landscape stands the corpse of Huygens, eye and emissary of a species that got off the ground of its own planet only 100 years ago and developed personal computers only 30 years ago. Today that species is poring over spectral, chemical, and electrical data from a world a billion miles away.

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