Titan - Key to Earth's Evolution?

By Emma Bakes
SETI Institute
posted: 06:25 am ET
17 October 2002

There are two Holy Grails in science today – the first is the pursuit of an answer to the question "How did the universe begin?’’ The second is "How did life begin, and is it a universal phenomenon?’’ My work is based around trying to find an answer to the second question. When I began my research, I found myself in the cold, dark reaches of the interstellar medium, a complex mixture of gas and dust that forms the cradle of new stars and planetary systems. With the advent of planet finding technology, scientists are finding these systems are scattered like precious jewels throughout our own galaxy. Likely, planetary systems and their promise of life stretch backwards into the infinite reaches of intergalactic space, so that life may be common to many galaxies.

Within the tenuous nebulosities of the interstellar medium may lay the building blocks of life – amino acids. My work has focused on this and, of course, on the universal presence of carbon, the basis of terrestrial life. Carbon forms the basis of terrestrial photopigments like chlorophyll, which helped to kick start the oxygenated atmosphere in the early Earth. It also forms the backbone of amino acids. If amino acids are present throughout our galaxy, then it is likely they are a universal phenomenon. This has profound ramifications for proving the potential universality of life based on these compounds. Indeed, it appears that tiny amounts of amino acids cocooned in the safe haven of icy interstellar dust grains can survive in the hostile regions between the stars.

In pursuit of further answers to the question of the origins of life, I steered my research inwards, to our own solar system. I focused on Titan, Saturn’s largest moon, well known as a prebiotic parallel to the atmosphere of early Earth. Could Titan hold the answer about the kind of chemistry that fuelled the evolution of life on the early Earth? It appears that Titan holds abundant and tantalizing clues, its dark organic haze holding the promise of life bearing chemistry. Titan is virtually waterless; however, adding water (i.e. simulating Earth-like conditions) to the macromolecular polymers within its haze yields amino acids. This gives us further evidence that the building blocks of life are ubiquitous and an inevitable result of a broad range of atmospheric chemistry.

Finally, I turned towards the Earth and have begun to focus my computation-based research on mechanisms with which to take the building blocks of life and form the DNA helix. This is the blueprint for life on Earth and I believe similar types of molecules form the basis of life on other terrestrial planets with aqueous environments. The helix is a naturally compact and symmetric structure, efficient for information storage, yet hardy and flexible enough to survive many hostile conditions on a newly formed planet. It has been a long journey home, and I find myself closer to helping our community find the answer to the question of the origins and universality of life. If we can use the signatures of helical molecules as a universal biomarker, then wherever there is life, its voice will be heard at these wavelengths, calling out to us. In future, with the development of highly sensitive biotechnology and detectors, SETI can search for these. Perhaps we will find that far from the Earth singing a quiet solo, the stars clamor with numerous voices in a cacophony that denotes the universality of life.