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Titan is Saturn’s Biggest Moon


Titan is the second biggest moon in the Solar System, second only to Jupiter’s moon Ganymede. The diameter of Titan is about 5,150 Kilometres.  This compares with the Planet Mercury with a diameter of around 4,880 Kilometres, but while Mercury has a lot of high density materials like Iron, Titan has more of the low density elements and compounds, and has a lower mass than Mercury.


The temperature at the surface of Titan averages about -180 degrees C (-291 degrees F.)  The coldest temperature ever recorded on Earth was -89.2 degrees C (-129 degrees F) at Vostok in the Australian Antarctic Territory; so Titan is cooler than the Earth.

Because of the low temperature, water is generally in the form of ice.  In fact, ice is an important type of rock, and sand there may well be made up of small pieces of ice.


Like the Earth’s Moon, Titan is tidally locked.  Only one face is visible from Saturn.


Titan has volcanoes. While on Earth, volcanoes can send out molten rock from the hot interior of the planet, on Saturn’s biggest moon, they can send out molten ice (water) together with many things dissolved in it, particularly Ammonia.


Titan and the Earth are the only known astronomical bodies in the Solar system with open bodies of liquid.  On Saturn’s big moon these are liquid Methane and possibly other hydrocarbons.


Titan has weather, including rain.  On the Earth the rain is liquid water while on Titan it is liquid Methane.  Some places on Earth have snow and on Titan hydrocarbon snow seems likely at the North Pole.


Both the Earth and Titan have an atmosphere with the main gas being Nitrogen.  On Earth, there is a lot of water vapour in the atmosphere while on Titan, the temperature is too cold for water vapour, but its place is largely taken by Methane.

Other gasses in Titan’s atmosphere include Carbon Dioxide, Ammonia and Hydrogen Cyanide. The pressure at Titan’s surface is about one and a half times that of the Earth at sea level.

Clouds and the Greenhouse Effect

Both Titan and the Earth have clouds which reflect some of the Sun’s rays and cool the surface, but both bodies have a significant greenhouse effect.  Many of the gasses causing this are the same although the most important one on the Earth is water vapour which is absent on Titan.  The most important one on Titan is Methane.

Titan and the Earth

There are many things in common between these two astronomical bodies.  One obvious difference is that Titan is colder; another one is that on Earth, life plays an important part.  But, is this different? Could there be life on Titan, playing a significant part in maintaining the conditions?

Life on Titan

There are many similarities between the Planet Earth and Saturn’s giant moon Titan, but on the Earth, life plays a major part in the various cycles.  Without life on Earth, specifically photosynthetic life, we would not have much Oxygen in our atmosphere.  On Earth, life also plays an important part in the hydrological cycle.

There may be thriving life on Titan, maintaining things like the balance between Methane and the other hydrocarbons and the amount of Nitrogen in the atmosphere.


The atmosphere of Titan has more Methane than appears likely from the amount of liquid Methane on the surface.  The most widely accepted explanation of this is that the Methane is being constantly replenished by cold volcanoes.  This is not the only possibility.


Both the Earth and Titan have a lot of Nitrogen in their atmospheres.  On the Earth, there is an important Nitrogen cycle involving life. Could this be the same on Titan?


Titan has little or no Oxygen in its atmosphere.  If any did form, it would tend to react with many of the other components of the atmosphere. Also, Titan gets only about one hundredth of the concentration of sunlight that the Earth gets.  It seems likely that any life on Titan is not photosynthetic.

Photosynthetic Life

On the Earth, Photosynthesis is at the base of the food chain.  Plants produce energy containing compounds; animals depend on plants, or on other animals that depend on plants,sometimes in a very complicated food chain.

Chemotrophic Life

However, in the last 100 years, it has come to be realised that not all life on Earth gets its energy from the Sun or from plants as we think of them.  There are many thriving ecosystems with the initial energy being provided by chemical sources.  These sources include Methane and other hydrocarbons. 

We know these are present on Titan.  The idea that life in some form exists on the surface of Titan is not impossible.

Underground Life

On the Earth, there is an enormous variety of life that lives underground.  This includes some bacteria that live very deep down and tolerates extreme conditions of heat.

There is evidence that Titan has underground reservoirs of liquid water with Ammonia and other compounds dissolved in it.  The conditions in these bodies of water are conducive to life similar to the life on Earth.

Does Titan Have Life?

We do not know; most scientists think it is too cold on the surface but we are constantly finding life in more extreme habitats than we had suspected a few years ago. Certainly NASA and other space agencies are hoping to find out.

How could it have got there?

There are several ways that life could have got to Titan.  The conditions on Titan are similar to those postulated for life to evolve from non-living chemicals, so it could have arisen independently of life on Earth.  Another way is for it to have got there from the Earth.

If you do not like the idea of life arising from non-living chemicals, the answer is much simpler.  If God created life on Earth suitable for our conditions, the Omnipotent Being could have created life on Titan suitable for its conditions.

All the elements necessary for life as we know it are present on Titan.  What we do not know is if life exists there.

Proving Life Does Not Exist

If life is found on a moon or planet, then we know there is life, but even if you spent a hundred years looking and failed to find any life, you still cannot be sure that no life exists there.  Finding life is proof it is there, but not finding it is not complete proof.

Although most scientists would guess that no life exists on the surface of Titan, perhaps we are looking at it too much from our own point of view.  We only know about one type of life; that on Earth. 

Consider an astronomer of Titan looking at the Earth and deciding if there is life on Earth, with only the life native to Titan as a guide.  Perhaps this astronomer might write:

Is There Life on Earth? (The view of an Astronomer of Titan)

Although the Planet Earth has all the elements necessary for life, I think that no conceivable life could exist in the atmosphere which contains the deadly poisonous gas Oxygen in large quantities, quite apart from the extremely high temperature, equal to the temperature of our molten lava. 

Exploration of Titan


Humans cannot see Saturn’s largest moon from the Earth without a telescope or binoculars, but with these, it is reasonably easy to see.  One problem is that it looks so close to Saturn.

Spaceships and Probes

Pioneer 11

Pioneer 11 was launched by an atlas rocket in 1973.  It passed within 43,000 Kilometres of Jupiter, receiving heavy radiation bombardment from the giant planet’s radiation belts.  The probe was saved by its extreme speed, and the Gravity slingshot effect increased its speed and it was on course for Saturn.

Pioneer 11 made some important discoveries about Saturn and took the first close-up pictures of Titan.  These were of low quality, but the probe was able to find the temperature of Titan.


Voyager 1 and Voyager two both went close enough to Titan to make some observations, but their instruments did not give all the information their designers had hoped. However, the information they sent back helped to design more suitable instruments.


The Cassini–Huygens probe is the most ambitious exploration of the Saturn system and Titan so far.

The Cassini orbiter was designed by NASA.  It has already returned important information about Saturn and its moons including Titan.

The Huygens Lander was designed by the European Space agency.  It was detached from Cassini and soft landed on the surface of Titan on January the 14th 2004.

Huygens sent back important information about the atmosphere and came to rest on what appears to be a currently dry flood plane.  It survived for several hours on the surface and sent back are the first close up pictures of any celestial body of the outer Solar System.

Living on Titan

Could Humans live on Saturn’s largest Moon,Titan?  Of course we could not survive without protection, but this applies to some places on the Earth where people live.


A single breath of Titan’s atmosphere would kill you.  There is no Oxygen, but there are some undesirable gases from the Human point of view including Ammonia and Hydrogen Cyanide.  However, these would not kill you.  The cold would.  With a temperature averaging below the lowest temperature ever recorded on the Earth, Titan is too cold for us. 
It is actually worse than outer space because the atmosphere would conduct heat away from our bodies, so we could not even survive in a normal space suit.  A Titan survival suit could be designed, but we should be looking at artificial habitats. 

Artificial Habitats

An artificial Human habitat on Titan might be constructed underground.  There seems to be some rock as we know it, but quite possibly we would use ice and line a cavern under the ice with some sort of plastic material made from the abundant hydrocarbons of this moon.  Everything we need could be made from readily available sources on Titan.


The Gravity of Titan is less than that of the Earth so people born there might have trouble adapting to the Earth’s gravity although they would be able to visit the Human colonies on Mars, Mercury and the other settled moons of the Solar System.

Air Pressure

The atmospheric pressure of Titan is higher than that of the Earth, so probably we would set the air pressure of our habitat at about one and three quarters times that of the Earth. There might be a little adjustment in the proportions of the different gasses needed, but the higher air pressure would help to guard against the poisonous air of Titan getting in.


With gravity only about a tenth of that of the Earth and a higher air pressure, a person could strap on wings and fly just using the strength of their arms.  Of course to do this you would have to have a large open space in your habitat.

Titan in Fiction

Titan is a very interesting place so there is nothing surprising about it being used by several authors in their stories.

Imperial Earth

Despite its title, much of the action in this most entertaining book by Arthur C. Clarke takes place on Titan. 

The book was published in 1975 so it is based on the knowledge of Titan at the time, but Mr. Clarke makes some quite shrewd guesses about conditions on Titan.  Some things he got wrong, including the temperature, but these things do not seriously affect the story.


Most of the author’s ideas about the habitats built by Humans are still relevant to the conditions as we know them.

Black Hole

Apart from the increased knowledge of Titan, science had made progress in other ways.  One noticeable thing is that at the time of writing, it was believed that stable mini black holes could exist.  Since then, the theoretical work done by Stephen Hawkins and others has shown that a black hole would need to be about the mass of the Earth to be reasonably stable.  The small black hole used in the drive of one of the space ships in the story would spontaneously explode in less than a second releasing all it energy.

Imperial Earth is a very good book, still well worth reading.


Titan also plays an important part in Ben Bova’s book, Saturn.  In this book, Titan has been discovered to have life.  Part of the story involves efforts to prevent the contamination of Titan by Earth organisms.

Half Life

Another good book involving Titan is Hal Clements’s Book, Half Life.

Titan Multispectural Overlay.  From the Cassini Probe.

Picture by NASA
Surface of Titan
Picture taken by Huygens lander.
Radar Image of Titan's Surface
Picture from NASA using data from the Cassini probe, at a distance of about 1200 miles.
Size of Titan next to the Earth
By Urhixidur via Wikimedia Commons. 
data from NASA
Representation of Methane Molecule by the  King of Hearts
An example of plants on the Earth.
Methane Ice Worm
This worm lives in the Gulf of Mexico, eating organisms that get their energy from Methane hydrates rather than from light.
Titan IVB/Centaur carrying the Cassini orbiter
with the Huygens probe.
The cassini probe with the Huygens lander was launched on October the 15th 1997.
Picture from NASA.
Pioneer 11
Picture from NASA