Target: Titan & Silicon-based life

18 03 2010

Move over, Mars.  According to new imagery from the Cassini spacecraft and new research recently published in the Journal of Cosmology, Saturn’s moon Titan may be the hottest exploration ticket in the Solar System.

Titan in front of Saturn. Credit: CICLOPS

Up until only five years ago, the massive moon Titan was one of the last great mysteries in our neighborhood of planets.  Itself bigger than the planet Mercury,  Titan’s freezing (-290 degrees!) smoggy, opaque, nitrogen-and-methane atmosphere was so think that we had no idea what its surface looked like.  It was only after the Cassini spacecraft settled into orbit in 2004 with advanced instruments that we were able to punch through the fog to see what was going on.

Radar images of Titan - dark areas suggest lakes/oceans of methane. Credit: CICLOPS

What we found was staggering.  Coastlines.  Erosion.  The most Earth-like environment to date.  As predicted nearly three decades ago but unproven until recently, Titan is the only other place in the solar system home to a hydrologic cycle of sorts.  I’m talking about lakes, streams, clouds, and rain.  But on Titan it isn’t water raining from the sky and running down mountainsides.  It’s far too cold, and water there is always a solid mineral, like silicon is here on Earth.  Instead, Titan’s “water” is liquid methane.

Utah? Rendering of possible Karst terrain on Titan. Credit: NASA/Malaska

While this is terribly good news for geologists interested in the processes of erosion (geomorphology), it was apparently bad news for hopeful astrobiologists.  Without liquid water, life as we know it can’t exist.  But hold that thought – Researcher Pabulo Rampelotto of Brazil’s Space Research Institute’s Exobiology and Biosphere Laboratory has identified an alternate biological chemistry that might support life on Titan…

Silicon-based Life

Our current understanding of physics, chemistry, and their roles in biology suggest that an organism could survive using an entirely non-carbon-based metabolism.  Silicon is a likely first place to look for alternatives.  Like carbon, (the chemical backbone of life as we know it,) silicon can form four bonds, stable bonds with itself and other elements, and long chemical chains known as silanes, which are very similar to the hydrocarbons essential to life on Earth.  Silicon is more reactive than carbon, which could make it optimal for extremely cold environments.

However, silanes spontaneously burn in the presence of oxygen, so an oxygen atmosphere would be deadly to any silicon-based life, and water as a solvent would be equally deadly for the same reason.  So, any environment with the potential for silicon-based life would have to be very cold, devoid of oxygen and water, but with another compatible solvent, such as liquid methane.  Sound familiar?

Of all places in the Solar System, Titan seems to be the only place active enough for life to currently exist.  -And even though Titan is definitely an alien and hostile place, it looks like we’ve identified a way for life there, as Crichton’s Ian Malcom famously put it, to “find a way.”


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