Titan

Huygens was a Dutch physicist and astronomer who first described the nature of Saturn's rings and discovered its moon Titan in 1655.

Huygens was a great figure in the fields of research when it came to mathematical physics, astronomy and optics, and among the founders of mechanics and optical physics. The telescope was invented by him that allowed one to tell apart the rings of Saturn, to make astrological observations about the planets, of the nebula of Orion and of the Moon. Huygens also preserved reports of the connection within the exact area of Tuscany; such reports were constituted by an attempt to define the character of the rings that surrounds Saturn.

It was long thought that Titan was the largest satellite in the solar system, but recent observations have shown that Titan's atmosphere is so thick that its solid surface is slightly smaller than Ganymede's. Titan is, however, bigger in size than Mercury and heavier than Pluto.

There is a thick atmosphere that surrounds Titan and the surface cannot be seen at all in light. Titan is quite similar in mass properties to Ganymede, Callisto, Triton (Neptuneís moon) and to some extent Pluto. We still donít know whether Titan has any internal structure like Ganymede or is identical like Callisto.

T itan is about half water ice and half rocky material. It is probably separated into several layers with a 3400 km rocky centre surrounded by several layers composed of different crystal forms of ice. Astrologists think that its centre may still be hot. Though similar in structure to Rhea and the rest of Saturn's moons, it is much denser. The reason for this is because of Titan being so large that its gravity compresses its interior ďpartsĒ.

Unique of all the satellites in the solar system, Titan has a large atmosphere. At the surface, its pressure is 50% higher than Earthsí and is mostly composed of molecular nitrogen, as is Earth, with 6% argon and a little amount methane. Astrologists say that there also have been traces of other compounds such as ethane, hydrogen cyanide, carbon dioxide and water. Titan's upper atmosphere is formed by methane and later is destroyed by sunlight. We can relate these results to the smog that we find over large cities, but here much thicker. There are many other similarities of Titan to the conditions that were on Earth when life was first getting started.

Titan has no magnetic field and sometimes orbits outside Saturn's magnetosphere. It is therefore directly exposed to the solar wind. This probably detaches and carries away some molecules from the top of the atmosphere.

Titan's temperature, at the surface, is about 94 K. Water and ice does not sublimate at this temperature although a lot of reactions going on the moon has resulted to a very thick fog.

In addition to the deep fog t here are scattered uneven clouds in Titan's atmosphere. These clouds are probably made out of methane, ethane or other simple organics compounds. Other more complex chemicals in small quantities must be responsible for the orange colour as seen from space.

Scientists also believe i tís likely that the ethane clouds would produce a rain of liquid ethane onto the surface, perhaps producing a large sea of ethane up to 1000 meters deep.

The Voyagers spacecrafts, a spacecraft that was sent in 1980 to discover Titan, were not able to penetrate the thick layers of clouds, but they did reveal that is one of the more interesting places in the solar system. What kind of landscape lies below the layers of clouds? What mysteries

Titan is one of the most interesting places to study extraterrestrial life and even the origin of life on Earth. Itís not likely that life could eventually grow on Titan because the lack of energy resources couldnít give interesting chemical reactions. This is interesting because you expect Titan to be rich in organic materials, possibly the richest in the whole solar system. Because of its similarities with Earth when it still was very young, we are hoping to find information about the time before life origins on Earth.

Scientists believe that sunbeam and particles from Saturnís own magnetosphere could start a chain reaction in Titanís atmosphere that produces complex organic compounds. Both Titan and young Earth consists with plenty of nitrogen and carbon based gases like methane and ethane, but none of them could produce oxygen. Actually free oxygen would have made the producing process of HCN difficult, a middle link at synthesis of adenine, one of four genetic codes that DNA is composed off.

The organic molecules in Titans atmosphere can sit together and make long chains, Polymers. They could then slowly, but surely, sink towards Titans surface. The layers of organic materials on Titans surface could supposably be several hundred meters thick. Despise the plenty of organic materials, Titan couldnít give birth to life. Unlike Earthís temperature, on Titan itís Ė180 degrees. Itís too cold for any life to occur there overall. Water, a terrific solvent, is frozen on Titan and therefore lack all possibilities to engage reactions of organic materials.

In very distance future, about 5 billion years from now, when the sun starts to blow up into a red giant, our Earth will probably burn up inside the sun. Maybe, then, the frozen water on Titan will melt and for a short time become a warm fruitful place to give birth to new life in our solar system. Titan will probably then get a reasonable temperature for us to live in.

Earth will become too hot for us and the conditions on Titan then might become like they are now, today.

So, should we all start planning to move from here? As we said before, this wonít occur until 5 billion years from now and who knows we might by then be living on other places such as Mars?

To get a better view of Titan and get better ideas about the evolution on the young Earth, we have sent a spacecraft called Cassini Huygen, 1997, towards Titan. On its way out in the space the spacecraft will use the gravity of Earth, Venus and Jupiter to finally reach Saturn and then Titan in October 2004. This is one of the most motivated spacecraft ever launched into space. Itís loaded with 12 powerful instruments, onboard the mother ship, and 6 on Huygenís probe. Together they can perform 27 diverse science investigations. The instruments on Huygen that actually will land on the surface of Titan will measure and analyse atmospheric structure, surface materials and take picture during the descent. The spacecraft is also able of analysing the magnetic fields, mass, electrical charges and densities of atomic particles on Titan. It can also measure the quantity and composition of dust particles on Titan. The high solution camera allows the spacecraft to take massive detailed images of not only Titan and Saturn, but also of other interesting objects while it is passing Jupiter and its satellites. The analyse results from Huygen will be sent to Cassini from the surface and from there back to Earth by one high-gain or two low-gain antennas under emergency situation.

Right now, autumn 2002, the spacecraft has passed Jupiter and is somewhere between Jupiter and Saturn. The spacecraft will arrive at Titan about 2 years from now and then it will start its scientific mission that will last for at least four years.

Titan was first observed in the IR from space Voyager in 1980, the spectrometers covered 200-1500 cm Ė1 of Titan. In 1997 they went again with ISO that took a full scan of Titanís 7to 27 m m spectral region. This is how we got to know about the surface composition and temperature of Titan.

If you want to compare Titan to other moons the most similar one is Ganymede, one Jupiterís satellite.

Titan and Ganymede are similar in both size and composition, itís an obvious question to wonder why Titan has so thick atmosphere and Ganymede has so little.

One possibility is that cooler temperatures in the solar nebula at Saturnís greater distance from the sun allowed more methane and ammoniac ice to condense. These ices are unstable than the water ice that makes up Jupiterís satellites and therefore are more likely to sublime and form an atmosphere. Alternatively, atmospheric cratering may have uncovered Ganymedeís atmosphere, but not Titanís.

Atmospheric cratering was probably more important on Ganymede than on Titan because Jupiterís stronger gravity accelerates impactors to higher speeds.††

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This is a picture of Titan compared to another moon Miranda. You can see here that they are almost the same in size, but because of the shadow coming on Titan it looks smaller.

To conclude everything of what we know about Titan is;

Huygen discovered Titan in 1655. The recent observations showed that Titan is not the largest moon in our solar system. It is a bit smaller than Ganymede. Titan is the only moon in our solar system with a thick atmosphere. The atmosphere consists of 90% nitrogen and at the surface the atmospheric pressure is 50% more than Earthsí. Titans is bigger than Mercury and its diameter is half as large as Earth. Titan is expected to be rich in organic compounds. Lakes of liquid ethane may cover Titanís surface, but this we are not sure off.

See Explanation.  Clicking on the picture will download 
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A picture of Ganymedes compared with Titan

The question that we still havenít answered is why Titan is so interesting for us?

Titan is similar to Earth in many ways. Just like Earth the most atmospheric gas is nitrogen and the pressure (as we have mentioned earlier) is only 50% greater than Earthsí. Titan has the biggest organic material on its surface in the solar system. If it has a higher temperature, life may grow on Titan just like it did on Earth once. That is why we have sent Huygen-Cassini to Titan to find out more about atmospheric gases and organic materials on its surface and even take picture of its landscapes.

What we hope to find out about Titan in our nearest future is;

  • What is the nature of Titanís surface?
  • What will Titanís surface tell us about the history of his moon?
  • Are there lakes or oceans on the surface of Titan?
  • Does it rain on Titan?
  • Are there rivers or other signs of erosions on Titanís surface?
  • Are there mountains or valleys on Titanís surface?
  • What direction does the wind blow, near and well above Titanís surface?
  • How much sunlight reaches Titanís surface?
  • What gases are present in Titanís atmosphere that is unknown to us?
  • What are the relative abundances and altitude distributions of atmospheric gases?
  • How similar are Titanís surface and atmosphere to early pre-life conditions on Earth?
  • Could life ever exist on Titan?

Answers to these questions could probably be a step closer to finding out about chances of life to occur in the extraordinary moon, Titan. Hopefully one day we will and have had come a giant step closer to find out of not being alone in our solar system.†

Here we have som fantasy pictures of a satellite landing on Titan and a whole new world opening for us.

You can see Saturn from this picture as† a fantasy in what we in distant future will accomplish

Finally we all think it has been a wonderful experience to have studied at an object this close and hope that you will like the results. We werenít able to find much pictures of Titan as not so many have been taken yet.

 

 

Sources:

astro.estec.esa.nl/SA-general/Projects/ First/Publ/2001/coustenisa.pdf

http://seds.lpl.arizona.edu/nineplanets/nineplanets/titan.html

The Cosmic Perspective† by Jeffrey Bennet, Megan Donahue, Nicholas Schneidar and Mark Voit.

PŚ resa i universum de yttre planeterna, utgiven av Det Ny Lademann A/S 1991

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