Amino acids could form in Titan's atmosphere

[Mayabird]

Life may have started sky high
Experiments suggest basic chemical ingredients formed in the upper atmosphere
By Ron Cowen
November 6th, 2010; Vol.178 #10 (p. 15)

A new experiment on Earth reveals that prebiological compounds may form in Titan’s upper atmosphere.

When it comes to determining exactly where in the solar system life began, things have never been so up in the air. Scientists over the past decade have suggested deep-sea hydrothermal vents, underground aquifers, partially frozen lakes and even comets as locations for the origin of life.

Now an experiment that simulates chemical reactions in the atmosphere of Titan, Saturn’s haze-shrouded moon, adds a new location to the list of unexpected places where life could have begun — in the sky.

The study used radio waves as an energy source, simulating the action of ultraviolet radiation from the sun that strikes the top of Titan’s thick atmosphere and breaks apart molecules such as methane and molecular nitrogen. The experiment is the first to produce amino acids and the nucleotide bases that make up DNA and RNA — the basic ingredients of life — without the need for liquid water, says Sarah Hörst of the University of Arizona in Tucson. She and her colleagues presented the findings in Pasadena, Calif., October 7 at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences.

The results suggest that Titan’s upper atmosphere, about 1,000 kilometers above the frigid moon’s surface, produces compounds capable of supporting life. And because planetary scientists believe that Titan represents a frozen snapshot of the early Earth, the study also indicates that terrestrial life might have formed within a primordial haze high above the planet rather than in a primordial soup on the surface, Hörst says.

Planetary scientist Jonathan Lunine of the University of Arizona, who was not part of the study, notes that the compounds found in the experiment “are relatively simple precursor molecules to life, and so there are a lot of additional steps between such molecules and life itself, most of which will likely require a liquid, such as water or methane.” However, he adds, everything that forms high in Titan’s atmosphere ends up in the moon’s lakes and seas of methane.

The study is provocative, Lunine says, because the Cassini spacecraft detected heavy ions in Titan’s atmosphere, but they were too massive for the craft’s instruments to identify. Amino acids were among the potential candidates for those heavy compounds, which were found in the terrestrial simulation.

To confirm that amino acids and nucleotide bases are actually produced in Titan’s atmosphere will require an orbiter that can carry instruments 100 to 200 kilometers deeper than Cassini does into Titan’s haze layer, Lunine says.

I just like reading about these sorts of things. This possibility hasn't been confirmed but we've found complex organic molecules in all sorts of places so far, like inside molecular clouds. The building blocks for life could very well be everywhere, which increases the chances that whatever step that comes next can happen.

Link

[Bottlestein]

^ Wouldn't the first step be trying to make RNA rather than DNA? It seems the delta-G for RNA should be much lower - and thus much more likely to be the first nucleic acid.

[Shinjai]

Wow. That's quite interesting. I wonder if they'll launch an orbiter with this sort of investigation in mind within my lifetime. Guess I'll just have to wait and see....

[Slacker]

There are actually two joint missions on the table between NASA, the EU, and JAX-one to Europa, and one to Titan. Currently, the Europa one has 'priority', in the sense they're funding and building it first, but in theory the Titan one could be up and on its way by 2020. The issue of course is that the whole thing assumes nobody cancels it between now and then.