Alien life on Titan?

I think you already know that Titan is the second largest moon in the solar system orbiting Saturn.  Recently, scientists have discovered clues of some sort of an alien life on Titan.

Titan has a wonderful atmosphere other than any moon in the solar system. It is 1.19 times massive as Earth’s overall and because of that its surface pressure is 1.45 times that of Earth’s. Like Earth Titan’s atmosphere is mostly nitrogen, about 95 percent near the surface whereas the Earth’s is 78 percent. The rest is methane, about 4.9 percent near the surface. Titan is far away from the sun; therefore it is in a frigid temperature of minus 179 degrees Celsius, cool enough to condense methane into liquid form.  Therefore methane condense in the atmosphere and decreases into a percentage of 1.4 in the stratosphere. Here is a comparison of Titan’s and Earth’s atmospheres.

The liquid methane rains occasionally slowly as thick brown snow and cause strong erosions on the surface. The Cassini spacecraft has even detected lakes filled by liquid methane in the polar regions as large as Caspian Sea here on the Earth.

Formation of chemical compounds

If you have learnt organic chemistry you know that methane in atmosphere is converted into other hydrocarbons by photochemical reactions due to sunlight. Therefore as calculated by the scientists the methane in Titan’s atmosphere must be converted into other complex hydrocarbons within 50 million years. But it is still out there flourishing in the atmosphere. This means that the loss of methane must somehow be resupplied by Titan itself.  Also beginning the high content of methane is also a puzzle. If titan’s atmosphere was originated from solar nebula it should be predominantly hydrogen and neon. If the origin is from cometary impacts there must be more carbon monoxide than methane. Hence many scientists have suggested that a special type of volcanoes called cryovolcanoes on Titan released methane. But there haven’t been discovered sufficient amount of cryovolcanoes to emit methane. Only one indirect surface feature called Sotra Facula is believed to be a cryovolcano.

Then what is the cause?

In June 2010,through computer models of the Titan’s atmosphere by Darrell Strobel of  Johns Hopkins University discovered a hydrogen molecule flow, about 10²⁵ molecules per second, formed as a byproduct of breaking methane and acetylene in the upper atmosphere to the surface. But surprisingly, based on the Cassini data the hydrogen gas is lost at the surface. Also even scientists expected to have large amounts of acetylene, as a layer of on the surface after falling from the upper atmosphere formed by chemical reactions. But once again based on the Cassini data acetylene was found very low levels at the surface.

Many speculations have been introduced to explain this scenario. The most interesting explanation is that a methane-based life form on Titan uses hydrogen with hydrocarbons like acetylene and ethane to produce energy. This revolutionary idea mainly came from astrobiologist Chris McKay and Heather Smith.  They suggest that while life on earth produce energy by burning glucose with oxygen resulting carbon dioxide and water according to this equation,

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O + Energy

methane-based life forms on the Titan like water-based life forms on the Earth derive energy by this process using hydrogen and acetylene.

C₂H₂ + 3H₂ --> 2CH₄ + Energy

Acetylene has been used because it produces the most energy. This really is a good suggestion for the apparent loss of hydrogen and acetylene on the surface of Titan like the amount of carbon dioxide in the Earth’s atmosphere varies in spring and autumn due to flora and fauna. This is merely a recycling process of carbon just like bacteria here on the earth in the nitrogen cycle. Even though biology has yet not discovered a methane-based life form this is really hypothetical.  Chris McKay has further said that these results of hydrogen and acetylene can also be due to human error, to a meteorological process or to some mineral catalyst. But such an effective catalyst under such a frigid temperature would be a great discovery. You can get a detailed view in here.

But researchers have pointed out that in many senses, hydrocarbon solvents like methane are better than water for managing complex organic chemical reactivity. To greatly suggest life on Titan, In October 2010, Sarah Horst of the University of Arizona reported finding the five nucleotide bases which are the building blocks of DNA and RNA, among the many compounds produced when energy was applied to a combination of gases like those in Titan's atmosphere. Horst also found amino acids, the building blocks of protein. She said it was the first time nucleotide bases and amino acids had been found in such an experiment without liquid water being present.

Also recently, data from Cassini suggested that there could be liquid ammonia mixed Water Ocean under the ice surface of Titan. As this medium has been highly suggested to harbor life, there might be life in it.

There is a possibility of such life form because there is water-based microbes called methanogens, producing methane through this process.

CO₂ + 4H₂ --> CH₄ + 2H₂O + Energy

Methanogens have been found on the earth under extreme conditions on the Earth in places like kilometers under the ice. Therefore it can be anticipated that there might be such life under the ice covers of Titan.

Titan has come to the first place in the Planetary Habitability index, made by scientists in the solar system other than the Earth. Therefore one day we might discover at least microbial type of extra-terrestrial life on Titan. It would change our view of the universe about the life as we know it.