Titan Provides Insights Into Evolution of Life on Earth
In a talk at the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society, Jonathan Lunine, Ph.D., said that Titan, the largest of Saturn's several dozen moons, is providing insights into the evolution of life unavailable elsewhere.
"Data sent back to Earth from space missions allow us to test an idea that underpins modern science's portrait of the origin of life on Earth," Lunine said. "We think that simple organic chemicals present on the primordial Earth, influenced by sunlight and other sources of energy, underwent reactions that produced more and more complex chemicals. At some point, they crossed a threshold — developing the ability to reproduce themselves. Could we test this theory in the lab? These processes have been underway on Titan for billions of years. We don't have a billion years in the lab. We don't even have a thousand years."
Titan is the only moon in the Solar System known to have an atmosphere. Like Earth, most of it consists of nitrogen, with methane the second-most abundant. Sunlight strikes Titan's upper atmosphere, breaking that compound into pieces that react with each other and nitrogen to form organic compounds. Those include ethane, acetylene, hydrogen cyanide, cyanoacetylene and others — all familiar terrestrial chemicals.
"We've got a very good inventory of what's there in the atmosphere," Lunine said. "What we've only recently begun to understand is the fate of these organics at the surface of Titan."
Lunine explained that for a long time, Mars had captured the public's and scientists' imagination as a possible location to find interesting organic chemistry and hints at life outside the Earth — and for good reason: It is an Earth-like planet relatively close to the Sun. But scientists have only found simple organic materials on the red planet.
Scientists now know, thanks to the joint NASA-ESA spacecraft that arrived at Saturn in 2004 after a seven-year journey through the Solar System, that Titan shares a surprising number of features with Earth. The enormous volumes of data that Cassini's 12 scientific instruments and the Huygens surface probe streamed back to Earth paint a complex picture of Titan's surface and the dense atmosphere that enshrouds it. Rivers flow into lakes. Wind sweeps across dunes. Giant storms brew, and clouds float across the hazy sky.
The catch is that Titan, nearly a billion miles from the Sun and a little larger than the Earth's own moon, is mostly frozen. It only receives about 1 percent of the sunlight that Earth gets. As a result, it is unimaginably frigid. At minus 290 degrees Fahrenheit — that's 160 degrees colder than the coldest recorded temperature in Antarctica — its water ice is rock solid, at least on the surface. And the rivers and lakes? They are made of liquid hydrocarbons, ethane and methane, which on balmy Earth are the main components of natural gas. Titan's deposits may be 10-100 times greater than all of Earth's oil and gas reserves, estimates suggest.
Lunine acknowledged funding from the Cassini Project, the NASA Astrobiology Institute and the John Templeton Foundation.
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