Life on Titan?

Life on Titan?

Titan might harbor life

Members of the Cassini-Huygens mission to Saturn’s moons have published the first of their findings from the second close flyby by the planetary probe of Saturn’s largest moon, Titan. They announced that they had found evidence that Titan might possess a liquid water ocean below several tens of kilometers of surface ice.1This discovery, combined with evidence that Titan possesses a panoply of “organics,” plus the possibility of volcanic activity, has spurred enthusiastic speculation that Titan might harbor life. The reasoning here is that all three of the fundamental requirements for life, namely liquid water, a supply of organic molecules, and an energy source, may all be present inside Titan.

The conclusion that Titan possesses a liquid water ocean is by no means certain. The Cassini-Huygens mission team drew their conclusion from their observations that Titan is not completely tidally locked to Saturn. Rather than Titan’s rotation period being identical to its period of revolution about Saturn, Titan spins 0.36 degrees faster than its revolutionary period. The team argued that this faster rotation could not exist if Titan’s crust were rigidly coupled to an internal solid core.

However, two other possible explanations for the faster spin exist: seasonal variations of wind directions near Titan’s surface and polar wobble, that is, periodic motion of Titan’s spin axis. The Cassini-Huygens team acknowledges these possibilities and recommends that the Cassini probe be returned for at least one more close flyby of Titan at a different seasonal epoch in Titan’s year to determine which of the three possibilities is correct.

Even if future measurements by the Cassini probe were to prove that Titan has a subterranean ocean, such a conclusion may not necessarily imply that life could possibly survive in that ocean. Just as deep ocean life on Earth requires the transport of oxidants from the surface to survive, so, too, any possible life inside Titan needs oxidants. Given how far Titan is from the Sun, oxidant production on its surface would be low, much lower than it is on Jupiter’s moon, Europa. An even more serious problem would be the implied thickness of Titan’s surface ice. At several tens of kilometers of thickness, Titan’s putative crust would not permit surface-produced oxidants to diffuse through the crust to the possible subterranean ocean–certainly not in the amounts required by life.

The proposed energy source for Titan’s possible life is not as viable as it may seem. While deep sea vents in Earth’s oceans do provide energy sources that help sustain the life that exists in their vicinities, their physical and chemical properties categorically rule out the possibility that life could ever originate there.2

Finally, the supply of organic molecules on Titan is not as helpful to life as some scientists suggest. While Titan’s upper atmosphere does reveal a diverse aggregate of hydrocarbon molecules, those hydrocarbons are temporary. During Titan’s seven-and-a-half year winter, no sunlight shines on its respective pole. The lack of sunlight means photolytic breakdown of hydrocarbons does not occur. Once sunlight reappears, the hydrocarbons disappear. Thus, the hydrocarbons produced in Titan’s upper atmosphere lack the locale, longevity, temperature, and abundance essential to foster the production of life molecules or even the simple building blocks of life molecules (amino acids, nucleotides, and five- and six-carbon sugars). Compounding the problem for Titan life enthusiasts is the fact that astronomers observe little or no oxygen, ammonia, or water either on Titan’s surface or in its atmosphere. Without high concentrations of these molecules, the hydrocarbons seen on Titan are irrelevant to both the origin or the sustenance of life.

Titan provides yet one more example of the notion that the more scientists learn about the solar system the more evidence they accumulate for the supernatural, super-intelligent design of Earth for the support of life. Research on Titan also strengthens the scientific case that life’s origin demands a supernatural explanation.

  1. Christophe Sotin and Gabriel Tobie, “Planetary Science: Titan’s Hidden Ocean,” Science 319 (March 21, 2008): 1629-30; Ralph D. Lorenz et al., “Titan’s Rotation Reveals an Internal Ocean and Changing Zonal Winds,” Science 319 (March 21, 2008): 1649-51.
  2. Fazale Rana and Hugh Ross, Origins of Life (Colorado Springs: NavPress, 2004): 102-03, 112-13, 149.