Chapter 5 - Titan Flashcards
What are two conditions that arise from the observed concentrations of different molecules in Titans atmosphere?
1 - Carbon containing molecules occur that would not be expected were the atmosphere in chemical equilibrium.
2 - the element nitrogen occurs on Titan mainly as a diatomic nitrogen molecule, whereas it occurs predominantly in the compound ammonia in the atmospheres of gas giants.
Equilibrium constant equation
For the equilibrium equation:
C + H2 = CH4
The equilibrium constant, k, can be calculated by the formula
K = [CH4] / [C] [H2]^2
Where the square brackets denote concentrations.
Why are there so many carbon chains in Titans atmosphere?
UV radiation from the sun causes CH bonds in methane to break, known as photodissososiation. This forms radicals which are highly reactive and will bond with other methane molecules or radicals to form hydrocarbons.
Typically methane will loose 2 H but 8% of the time it will lose 3 H the remaining CH radical is needed to create long carbon chains.
What is a radical?
A molecule which has no charge but has an unpaired electron so it can form chemical bonds readily.
How is atomic N formed in titans atmosphere?
It can be formed due to photodissasosiation from sunlight or by N2 colliding with elections from cosmic rays.
Why is atomic N important in titans atmosphere?
Atomic N is required to allow nitriles (CN) to be formed. Nitriles are a form of organic molecule.
Why is nitrogen found in molecular form as opposed to ammonia in titans atmosphere.
Ammonia is broken down by photodissasosiation. During photodissociation the hydrogen is lost to space due to titans low escape velocity.
Two NH3 molecules can then react to form molecular nitrogen and hydrogen.
If NH2 is formed, 2 NH2 can react to form hydrazine. If the hydrazine remains gaseous it can undergo a series of photodissociation reactions resulting in N2H2 which breaks down to N2 and H2. The hydrogen escapes to space leaving the nitrogen..
What causes the haze on Titan?
The haze consists of mainly hydrocarbons and nitriles which are referred to as tholin. These particles formed of C, H and N are thought to have formed by a process similar to that of the hydrocarbons.
These particles are homogenous actors all altitudes.
Does Titan have a stratosphere?
Titan does contain a stratosphere which is where the temperature increases altitude. The active molecule in Titan atmosphere is methane as opposed to the ozone molecules we have on earth.
Does titan contain liquid on its surface?
Titan does contain liquid at surface which was discovered using radar from Cassini. The lakes and oceans are mainly situated towards the poles and consist of liquid methane and ethane.
What evidence does the landscape on titan provide for a liquid methane cycle?
Images on the surface of Titan show round pebbles and sound sized grains that appear to be flood deposits. When the lander impacted the surface it had a similar force to landing in damp sand. finally clear evidence of riverbeds have been found on the surface of Titan.
How is it believed that methane is replenished in the atmosphere on Titan?
It is now thought that methane is released from within Titan by outgassing.
The presence of Ar40 in the atmosphere proves that outgassing occurs and is thought to occur due to effusive cryovolcanism.
How could methane have been incorporated pirated into Titan?
If the conditions at the time of formation were very cold the methane could have been trapped in ice as clathrate.
If the conditions were warmer a reaction that occurs between water and rock (known as serpentinization) can produce methane.
What is the composition of Titans interior?
Indirect measurements of Titan interior structure suggests that, below the ice, the interior is largely undifferentiated, similar to Jupiter‘s moon Callisto.
What is the structure of Titan?
The outer shell of Titan is believed to be decoupled from its interior by a liquid layer, allowing it to rotate slightly faster than the interior as a result of frictional wind drag.
The liquid layer is thought to be water that is highly concentrated with salt and ammonia which lower the freezing point allowing it to stay liquid.
The core is thought to be undifferentiated rock and ice.
