Well it looks like the evolution of life and Saturn’s moon, Titan, were topic of discussion in Indianapolis this past week at the 246th National Meeting & Exposition of the American Chemical Society (ACS). Jonathan Lunine, Ph.D., from Cornell University presented data on Titan and discussed how it provides insights into the evolution of life unavailable elsewhere.
Above: Artist's concept of Cassini around Saturn (from wiki commons)
In materials released by the American Chemical Society, Lunine said, "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 continue, "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."
Much of the data coming back from NASA’s Cassini Project indicates that Titan shares a surprising number of features with Earth. Recent research has provided hints that liquid water may exist deep under Titan's surface. Other data suggest that areas of Titan's seafloor may possess hydrothermal vents, similar to Earth's seafloors. On Earth, these areas are a conduit into the planet’s interior, allowing hot, mineral-rich water to spew out, fostering an amazing diversity strange life.
Compared to other areas on Earth’s seafloor, submarine hydrothermal vents are biologically more productive. They often possess complex communities which are completely dependent on the chemicals that come from these vents.
Above: Hydrothermal vent on Earth (from wiki commons)
Bacteria and other prokaryotes (i.e. archaea), form the base of the ecosystem. These organisms use sulfur, specifically hydrogen sulfide, to create carbohydrates, in a process similar to photosynthesis. Instead of splitting water as the initial step, these deep-sea organisms split hydrogen sulfide (H2S) as the first step in the presence of carbon dioxide. Ultimately they produce sugars as a chemical form of energy and release solid sulfur, instead of oxygen, as a waste product. Before the discovery of these ecosystems, we assumed that all life was dependent on the sun, but the complex of community of prokaryotes and animals in these areas demonstrates otherwise.
What’s so fascinating about this suggestion is that there are some who hypothesize that hydrothermal vents were the areas of life’s origin on Earth. In the late 1980s, Günter Wächtershäuser proposed the iron-sulfur world theory, suggesting that life might have originated at hydrothermal vents. Others added that the creation of amino acids, the building blocks of life, could be created in the deep Earth and then introduced to cooler waters where early protocells could have first formed.
If these ideas are correct, such that life, or proto-life, could form in areas around hydrothermal vents of methane-rich, liquid water, then future explorations to Titan could yield our first evidence of life on another planet. This dim, methane rich moon, may have what it takes to be the home for life, even today.