September 13, 2013
Saturn Moon May Provide Answers On How Life Evolved On Earth
April Flowers for redOrbit.com - Your Universe Online
A most unlikely venue, nearly one billion miles away, is giving scientists glimpses of the events that nurtured life on Earth more than 3.5 billion years ago.Jonathan Lunine, PhD, from Cornell University, is the leader of an international effort to understand Titan, one of the most unusual moons in the Solar System. Lunine presented the findings of the more than 260 scientists involved with the project at the 246th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society.
According to Lunine, the largest of Saturn's several dozen moons, Titan, 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."
Lunine is part of the 260 scientists attached to the Cassini-Huygens mission. He explained that only two celestial objects in the Solar System - Titan and Earth - have the largest amounts of organic substances on their surfaces to provide such information. On Earth, such substances have been cycled through living things countless times. In contrast, Titan's organic materials, including deposits of methane and other hydrocarbons as large as some of the Great Lakes, are in pristine condition. As far as anyone knows, they have never been in contact with life.
Titan is the only moon in the Solar System known to have an atmosphere, and like Earth's, it is mostly nitrogen. Methane is the second-most abundant element in both atmospheres as well. Methane is broken into pieces that react with each other and the nitrogen to form organic compounds as sunlight strikes the upper atmosphere of Titan. These organic compounds 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."
For a long time, according to Lunine, Mars has captured public and scientific imagination as a possible location to find interesting organic chemistry and hints at life outside the Earth. They had good reason for believing this -- Mars is an Earth-like planet relatively close to the Sun. So far, however, scientists have only found simple organic materials on the Red Planet.
Fascinating hints have been uncovered in recent research, suggesting that liquid water may exist deep under Titan's surface. Other studies have suggested that regions of Titan's seafloor may be similar to areas of Earth's seafloors where hydrothermal vents exist. On Earth, these passageways into the interior of the planet spout hot, mineral-rich water that fosters an array of once-unknown forms of life.
Thanks to the joint NASA/ESA Cassini-Huygens mission that arrived at Saturn in 2004 after a seven-year journey through the Solar System, scientists have discovered that Titan shares a surprising number of features with Earth.
Cassini has returned great volumes of data from its 12 scientific instruments and the surface probe on the Huygens. This data paint a complex picture of Titan's surface and the dense atmosphere that enshrouds it. Titan's surface is dynamic: rivers flow into lakes, wind sweeps across dunes, giant storms brew, and clouds float across the hazy sky.
Nearly a billion miles from the Sun and slightly larger than the Earth's own moon, the main challenge with Titan is that it is mostly frozen. Only one percent of the sunlight that reaches Earth makes it to Titan's surface, meaning that it becomes unimaginably frigid.
At temperatures that are 160 degrees colder than the coldest ever recorded in Antarctica - minus 290 degrees Fahrenheit - the water on Titan is rock solid, at least on the surface. The rivers and lakes are made of liquid hydrocarbon, 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.