Are We Alone? New Hope in the Search for Alien Life

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Listen to astrobiologist David Grinspoon on the Popular Mechanics Show as he discusses the likely hideouts for life in the universe. Download and listen now. (click to subscribe)

There are many strange landscapes in the solar system, but perhaps none stranger than that of Titan, Saturn’s largest moon. Deserts blanket Titan for hundreds of miles, rippling with wind-sculpted dunes that rise more than 300 ft. Images taken by the Cassini spacecraft over the past two years also reveal riverbeds sculpted by liquid methane, canyons, and what appear to be a volcano and a shoreline. When Cassini dropped the Huygens probe onto Titan’s surface in 2005, the 701-pound craft landed in a substance with the consistency of wet sand. Shrouding it all is a smoggy, orange-hued atmosphere 10 times thicker than Earth’s and made up of complex organic molecules.

“Titan is so cool,” says Peter Ward, who leads NASA-funded astrobiology research at the University of Washington. “Titan is the most exciting place in the solar system astrobiologically. It has the most exciting chemistry set in our solar system by far. If there’s life on Titan, it’s alien life--really alien life.”

But finding microorganisms on Titan--or anywhere in the universe--is no easy task. Titan has carbon-based molecules, for example, which is one of the necessary ingredients for life as we know it. But the recipe may be different there than it is here on Earth.

“Methane plays the same meteorological role on Titan as water does on Earth. So what would life look like if it drank a glass of methane in the morning, rather than a glass of Florida orange juice?” asks molecular biologist Steven Benner, a distinguished fellow at the Foundation for Applied Molecular Evolution. No one knows, but it is one of many questions intriguing astrobiologists.

Over the past few years, spacecraft such as Cassini have provided an unprecedented look at alien landscapes, boosting the search for life throughout the solar system to new levels. But according to Benner and other scientists, some of the most insightful research is taking place right here on Earth. Life has been found in the unlikeliest of habitats, from South Pole snow to hot springs in Yellowstone. “I’ve always been amazed that it’s so hard to go any place on this planet where there’s energy and water and not find life,” Benner says. “It’s everywhere.”

Understanding the conditions in which life can thrive here helps to shed light on where it might survive elsewhere. Just how dry, cold, hot, ancient and unorthodox can life get? The answers will help determine whether we have extraterrestrial neighbors--and just where in the solar system, or beyond, they might be.