Saturday, June 12, 2010

Methanogenic Life on Titan?

Saturn's moon Titan is one of my absolute favorite objects in our solar system. The above image, taken by the Casini spacecraft using infrared imaging to cut through Titans thick atmosphere, reveals the sun glinting off the surface of what are believed to be standing lakes or even an ocean of methane near Titans north pole. The largest of Saturn's moons, Titan is the only natural satellite known to have a dense atmosphere,1.19 times as massive as Earth's, and is the only object other than Earth for which clear evidence of stable bodies of surface liquid exists.

Titan's dense hazy atmosphere made it impossible for the first probes to pass near enough to image the moon to penetrate through to the surface, until The Cassini–Huygens spacecraft reached Saturn on July 1, 2004 and began the process of mapping it's surface by radar. On January 14, 2005,The Huygens Probe touched down on the surface of Titan after a three hour descent through the moons thick atmosphere, revealing that many of the moon's surface features seemed to have been formed by flowing liquid. Now, new evidence has arisen seeming to suggest there may be life on Titan, or so the headlines would have you believe. But as with the recent hype surrounding the creation of so called synthetic life, the evidence for life on Titan has been greatly exaggerated for the sake of a story.

The first thing you need to understand is that Titan is extremely cold, around minus 290 degrees Fahrenheit or minus 179 degrees Celsius, so water cannot exist on the surface of Titan in liquid form. That means any organism that did live on Titan would have evolved to use a substance which would remain liquid at those temperatures, methane being the most likely candidate. While there are liquid-water-based microbes on Earth that thrive on methane or produce it as a waste product, methane based life remains speculative.

All of this speculation is the result of two recently released papers based on the analysis of chemical data returned by the Casini spacecraft. The first paper by Darrell Strobel suggests that hydrogen molecules flowing down through Titan's atmosphere are disappearing on the surface. The second paper by Roger Clark maps hydrocarbons on Titan's surface and finds a surprising lack of acetylene. Both substances would be essential to methanogenic life which would use hydrogen as we do oxygen and could potentially consume acetylene as food, thus accounting for the seeming lack of each substance in Casini's data. Could all this be evidence that methane based life exists on Titan? Absolutely. But as always Occam's razor applies and it's far more likely that further analysis will reveal a less spectacular reason for the seeming anomalies.

Here on earth, the existence of creatures living hundreds of feet below the ice in the arctic, thriving in poisonous lakes in under ground caves or living in sulfur vents in the deep ocean make it clear that life can adapt to most anything, and I personally believe we will find life outside of Earth. Weather that life will be as simple as some alien cave slime or microbe or as exotic as silicone based lifeforms thriving in oceans of methane I certainly don't know. But as tantalizing as it may be, it's too soon to say that Casini's most recent findings represent proof of such life on Titan.

Links and Additional Content
First, check out the and Universe Today articles on this story, which were my primary sources for today's entry then, this video from the ESA which condenses the hours of data the Huygens probe collected down to 4 mins and 40 seconds.(The sounds added to this video get annoying you might want to consider muting it.)

Video posted by Youtube user:nequest
Image Credit:NASA

No comments:

Post a Comment