In Greek Mythology, the gods that ruled the Earth and heavens before the age of man. Eventually overthrown by the more common Greek gods, the Olympians, led by Zeus.

The Titans represented the blind forces of nature worshipped by primitive man before the gods of the great civilisations were conceived. The Olympians had to chain them in the deepest level of the underworld to secure the world for civilisation.

Not all Titans were malign however, one Prometheus rebelled against the gods and stole fire from them, giving it to mankind as a gift he initiated civilisation. For this he was punished by Zeus by being chained to a rock while a vulture pecked at his liver. He remained there till rescued by Hercules.

In general the Titans were seen as evil rebels, and this led them to be cast as the primary forces of evil in the Orphic Mysteries. They rebeled against the Apollonian harmony of a primal 'Eden', brought conflict into Nature and dismembered the supreme spiritual being Dionysus. On being blasted to bits by Zeus the remains of the Titans along with divine fragments of Dionysus were formed into mankind.

Titans include:


One of Saturn's moons. See other writeup for technical facts.

Titan is the only planetary moon with a substantial atmosphere. It has been studied by several scientists, most notably the Dutch astronomer Gerard Peter Kuiper.

There are many similarities with the Earth's atmosphere. In both atmospheres molecular nitrogen is the main constituent and the surface pressure has an order of 1 bar. Several other trace gases like methane, hydrogen, carbon monoxide, and several molecules are detected. Due to the supposed similarity with the proto-atmosphere of the Earth, paleoclimatologists and exobiologists are interested in the special circumstances which allowed the evolution of the life on the Earth. Especially the complex chemistry of Titan's atmosphere could be the key for the understanding of the evolutional history.

In 1980 Titan has been observed closer by Voyager 1 which also sent the first colour pictures of Titan to the Earth. Voyager 1 identified that Titan carries the national colour of his Dutch discoverer Christiaan Huygens, namely orange. This colour is the result of the thick stratospheric organic haze layer. This thick haze layer covers the whole moon, making an observation of the surface in the visible spectrum impossible. Consequently, many speculations about the surface property arised, ranging from a global ethane ocean to a dry rock surface. This mystery has not been unveiled up to this day.

Titan does not have an own magnetic field, but due to the dense atmosphere a wide-spread ionosphere which interacts with the arriving plasma. Since Titan can be located outside the magnetosphere of Saturn, it is exposed alternately to the solar wind and Saturn's magnetospheric plasma. This large variation of plasma interaction makes Titan quite fascinating.

Titan is a science fiction novel by Stephen Baxter

2004: NASA'S CASSINI probe reaches Saturn, discovering evidence of life on the moon Titan and the amazing story of Titan begins ...

Thanks to one woman's will to succeed and the triumph of a dream over bureaucracy and fear, frail humans are hurled on a ten-year one-way trip to investigate evidence of life on Saturn's moon, Titan. Their ship is patched together from the remnants of fifty years of spaceflight, and they leave earth in the face of violent opposition from the military. Over the ten year journey the political situation worsens between China and America. As the crew near the edge of the solar system, news from earth brings them close to the edge of sanity ...

Titans is sometimes used to translate the Sanskrit word Asura. The Asuras were a race of beings almost as powerful as the Gods, but in constant war against them. Much like the Nordic giants.

Some people translate Asura as demon, but I think the Asuras were not would be thought of as Satanic, so that calling them demons is a bit of an exageration.

The following is a short paper entitled The Origin of Titan's Atmosphere I wrote for a planetary physics class I took several years ago (1996, I think). I found it in my notebook recently when looking for something else and reread it. The professor liked it, so I present it to you for posterity.

1: Introduction

Titan is a unique object in our solar system. It is not only the second-largest satellite among the planets, but it also has the second-densest atmosphere of all the terrestrial planets and satellites, barring only Venus. Titan's atmosphere is primarily molecular nitrogen and methane, with trace amounts of other compounds including hydrocarbons and "smog," like the hydrocarbons that give the Jovian planets their color. In addition, Titan's atmosphere is very cold (about 100 kelvins), which not only keeps the rate of thermal escape of the atmosphere very low, but also keeps many other atmospheric constituents (or possible constituents) frozen on the surface. The presence of a significant atmosphere on Titan was suspected as early as the turn of this century, and confirmed by Kuiper by 1944. While the atmosphere has been well-studied throughout the latter half of this century (especially by the Voyager 1 rendezvous), there is still debate about the origin of the dense, nitrogen-rich atmosphere. Currently there are several theories on the origin of Titan's atmosphere, none of which have been conclusively proven or dismissed. In this paper, I will summarize and discuss each of these theories. In addition, I will discuss the upcoming Cassini/Huygens mission to Saturn and Titan, which may offer more clues to the origin of Titan's atmosphere.

Section 2 of this paper will give a brief overview of the status of observations and experimentation on the atmosphere of Titan. Section 3 will discuss current theories on the formation of Titan's atmosphere and the pros and cons of each. Section 4 will discuss the Cassini/Huygens probe, and the contributions which it may make to the debate over Titan's atmosphere.

2: Observations of Titan's atmosphere

The pre-Voyager and Voyager observations are thoroughly discussed in Hunten (1984) and Owen (1982), and will be summarized here. Suggestions of an atmosphere were first made by Solà in 1908 and were found to be theoretically possible by Jeans in 1925, but the existence of an atmosphere was not proven until Kuiper observed methane red and near-IR absorption lines in 1944. This discovery was significant not only because it requires a dense atmosphere with a significant fraction of methane, but because it also requires that the atmosphere be chemically evolved, since methane requires hydrogen in the presence of carbon, and molecular and atomic hydrogen would have escaped from Titan's weak gravitational field since the formation of the solar system. Laboratory experiments assuming a pure methane atmosphere again predicted a dense atmosphere, but one much less dense than is now known.

Until the 1970's, few significant advances were made in the study of Titan, other than the possible detection of mid-infrared bands of more hydrocarbon compounds and the development of several atmospheric models. In the 1970's however, major refinements to the popular theories about the atmosphere were made. The detection of vibration-rotation spectral bands of hydrocarbons such as acetylene, ethane, and deuterated methane were confirmed by better high-resolution IR spectra, and wavelength-dependent continuum opacities suggested the presence of a rich hydrocarbon "smog" in the atmosphere. However, ammonia -- common in the giant planets -- was not detected. In addition, radio observations of Titan set its temperature at 87 K, cold enough for liquid methane and ethane on the surface. Before the Voyager encounter, we therefore knew that Titan had a cold, dense atmosphere, rich in methane and other hydrocarbon compounds. At this point, the presence of molecular nitrogen had not been confirmed, although it was strongly suspected to be the major atmospheric constituent.

Finally, the Voyager 1 and 2 encounters set firm limits on the temperature, structure and composition of Titan's atmosphere. UV observations of the upper atmosphere and radio occultation measurements of the mean molecular weight determined that molecular nitrogen is the primary constituent of the atmosphere with a surface pressure of about 1.5 bars. Infrared measurements set the surface temperature at 95 K. Radio occultation measurements also established the structure of the atmosphere, with a well defined stratospheric temperature minimum of about 75 K. In addition, Voyager also established that the partial pressure of methane was low in comparison to that of nitrogen, so the presence of significant condensed methane on the surface of Titan is unlikely. Finally, precise measurements of the mean molecular weight indicated that it is slightly higher than 28, indicating the presence of heavier gases, possibly argon.

While we now have a fairly complete picture of Titan's atmosphere, we do not know how and why it formed. As mentioned in the introduction, Titan has an atmosphere denser than all of the terrestrial planets and satellites other than Venus, so it is likely that its atmosphere formed under special conditions, probably at or near the beginning of the solar system. Currently, there are several theories on the origin of Titan's atmosphere, including accretion of gas from the solar nebula, and outgassing of atmospheric constituents from the interior. Currently, observations made to date cannot confirm or eliminate any of these theories. The following sections will discuss conditions during the formation of Titan and theories on the development of a Titanian atmosphere, along with constraints on the likelihood of these theories being correct.

3: The origin of Titan's atmosphere

3.1: Nebular composition and the origin of Titan

Before discussing theories on the origin of Titan's atmosphere, the conditions near Saturn and Titan at the time the planets and satellites formed should be discussed, as they are crucial to the formation of Titan itself as well as its atmosphere. As was discussed in lecture, the materials composing the nebular disk at the time the Sun and planets formed had a composition gradient of solids and of molecular species dependent upon the temperature in the disk. This also implies a radial dependence upon distance from the Sun. At the distance of Saturn, the composition of Saturn's primordial accretion disk was a combination of rocky materials and volatile species. The temperature of the nebula due to the Sun would have been roughly

Tambient = (500 K/AU)/RSaturn's orbit) ~ 50 K,

which implies that in the absence of an accreting Saturn, the local nebula would have been cold enough to form ices, hydrates, and clathrates of volatile species in addition to dust grains and rocky materials.

IR radiation from the accreting proto-Saturn and proto-Titan could substantially increase this temperature, but there would still be volatile species out of which to create the atmosphere. Prinn and Fegley (1981) derived the chemical equilibrium conditions for both hot and cold accreting nebulae. They found that under the conditions expected around the accreting Jovian planets and their satellites, the levels of volatile gases and hydrocarbons is actually enhanced in some cases. The result is that the nebula out of which Titan (and possibly its atmosphere) formed would be rich in methane and ammonia, and depleted in simpler species like CO, hydrogen, and nitrogen. In this case, the rocky material and water ice out of which Titan likely formed would be very rich in both methane and ammonia. This is crucial to all of the theories of the formation of Titan's atmosphere, with the only difference being in where the majority of the atmosphere came from - either from direct accretion, by outgassing and cryogenic volcanism, or by impactors releasing hydrocarbons from the surface clathrate/hydrate ices.

3.2: Formation of Titan's atmosphere

Currently, there are three possible explanations (with some variations) to account for Titan's dense atmosphere: that it formed via accretion of nebular gas onto the developing proto-Titan, that it formed via cryogenic volcanism and outgassing of warm materials from Titan's core, or that it formed via melting and outgassing caused by impactors or accretion energy. In all of the theories for the formation of the atmosphere, it formed during or soon after Titan itself grew out of the nebula forming Saturn, and in most cases, the theories most consistent with observations involve some combination of accretion and outgassing. The key points in determining whether the theories are valid are that they not only match what we know from previous observations and the Voyager flybys, but that they are physically possible. Each theory and variations will be discussed along these lines in the following sections.

3.2.1: Accretion of the Atmosphere
This theory states that Titan's atmosphere was primarily accreted from the proto-Saturn and proto-Titan nebulae. In the case of accretion, the nebula composed of either molecular nitrogen and methane or ammonia and methane is accreted directly onto the surface forming a dense atmosphere. In the case of the latter, the ammonia could be photodissociated via solar radiation over a long period of time (~ 0.1 - 1 Gigayear), generating the current nitrogen-rich atmosphere, with some methane. (The resulting molecular hydrogen from photodissociation of ammonia would escape via Jeans escape.) This has two problems. First it would require that Titan accreted significantly more ammonia than methane, since the measured nitrogen column is much higher than the methane column. This is not likely since there would not be significantly more ammonia than methane in the nebula.
Second, and most importantly, the observed abundances of elements other than nitrogen in the atmosphere do not match the cosmic abundances expected from simple accretion from the nebula. One example mentioned by Owen (1982) is the abundance of neon. The mean molecular weight is very close to 28, the molecular weight of molecular nitrogen. However, neon has nearly the same cosmic abundance as nitrogen, but it cannot be a major constituent of Titan's atmosphere since the mean molecular weight would be much lower. It might be possible to combine several gases such as neon and argon to create a local mean molecular weight of 28, but this would be impossible to maintain over the entire height of the atmosphere. Therefore, an atmosphere created by simple accretion of the nebula is not likely.
3.2.2: Cryogenic volcanism and outgassing
The outgassing theory states that Titan's atmosphere arose primarily via outgassing of volatiles accreted onto the surface as clathrates or hydrates. In this scenario, volatiles are accreted onto the surface primarily as clathrates, or are incorporated into surface clathrates during the accretion phase and into clathrates making up the interior. The atmosphere could then be fully explained by outgassing of methane and ammonia. This scenario actually requires the presence of a small accreted atmosphere during the outgassing phase because a tenuous atmosphere created only by outgassing and melting of surface ice would likely take longer to grow (due to heat loss) and may not form at all.
Outgassing might have occurred in several ways. Hunten (1984) describes a scenario where accreted ammonia and methane clathrates are melted by the relatively high surface temperature due to accretion. The resulting ocean of water, ammonia and methane releases a significant amount of methane and ammonia into the atmosphere, and the ammonia is converted to nitrogen and hydrogen via photodissociation. As accretion stops, the surface temperature drops, and as the ocean freezes, it reincorporates the atmospheric methane into clathrate much faster than it reincorporates nitrogen. The result is a nitrogen-rich, cold atmosphere with some methane and other trace gases.
Another possibility is discussed by Lunine and Stevenson (1987) whereby a dense atmosphere does not form immediately, but instead comes from core material in a cryogenic volcanic process. Their scenario depends upon the fact that Titan's interior would (most probably) not have been stably stratified immediately after accretion, such that there may have been significant layers of dense rock on top of icy material in the core. Since this would be unstable, the core of Titan would "overturn" generating significant heating, and allowing methane and ammonia trapped in clathrates in the interior to percolate through the outer layers and be outgassed. Again, generation of nitrogen could occur via photodissociation, or as the authors suggested, via shock heating by impactors such as comets.
3.2.3: Formation of atmosphere by impactors
This theory has been suggested by several authors (Lunine and Stevenson (1987), Jones and Lewis (1987)); it suggests that the atmosphere could have been generated via shock-heating of the ice or liquid surface of Titan caused by infalling planetesimals or comets. As mentioned in the preceeding section, impactors would not only liberate volatile gases locked in surface clathrates but they would also be able to convert ammonia to nitrogen, and thus explain the current atmosphere. (McKay et al. 1988) This process probably would have been common during the accretion phase while there was still a significant amount of material in the Saturnian and Titanian accretion disks, so it is possible that the atmosphere may have been generated in this way. However, Hunten claims the process is less likely to generate a dense atmosphere than it is to eject mass from Titan. Massive impactors moving at high velocity relative to Titan (e.g. comets) would likely have enough energy to eject a significant portion of Titan's mass and atmosphere.

4: Future Prospects - the Cassini/Huygens probe

Of the three theories for the formation of Titan's atmosphere, it seems that the outgassing/volcanism theory is most likely to be correct. However, there is still significant debate whether the formation of the present atmosphere was driven by vaporization of methane and ammonia from a primordial atmosphere, by outgassing from Titan's interior, or some combination of the two. One way that this might be resolved is with the Huygens probe on the Cassini mission to Saturn, due to drop into Titan's atmosphere in 2004. The Huygens probe has several instruments designed to study the atmosphere and surface in great detail; one of these, the Gas Chromatograph and Mass Spectrometer (GCMS) has the potential to help determine which model for the formation of the atmosphere is correct.

One of the most-discussed methods for distinguishing between formation models is the abundance of argon and its isotopes in the Titanian atmosphere. We know that the mean molecular weight in the atmosphere is slightly higher than that of pure nitrogen, so there must be material heavier than nitrogen in the atmosphere; currently, argon is a strong candidate for this component. However its origin is ambiguous since it may have either been accreted with the clathrates out of which the atmosphere was formed, or it might have been outgassed from Titan's core as a radioactive decay product of potassium. Therefore the abundance of argon, and more specifically of each of its isotopes, is linked to the formation process that generated Titan's atmosphere. The GCMS experiment on Huygens may be able to distinguish between the two possibilities by measuring the ratios of the more abundant isotope argon-36, and the potassium-40 decay product argon-40. If argon-36 is the primary argon isotope observed on Titan, then it is more likely that the argon was accreted (since argon-36 is the most cosmically abundant isotope of argon). If argon-40 is the most abundant, then it is probable that it arose from outgassing of potassium by volcanic silicates from the core regions, where some of the potassium would have been radioactive potassium-40. (Engel and Lunine 1994)

There are several other instruments on board Huygens which may also help. Engel and Lunine also mention mention the possibility of obtaining images of the surface with the Descent Imager and Spectral Radiometer (DISR). It is possible that volcanic outflows may be visible on the surface, which would be a strong indicator that outflows may have played a role in the formation of the atmosphere. The DISR would be capable of imaging these regions, assuming they would be located in the region where the Huygens probe will land. In addition, the Surface Science Package (SSP) may be able to make compositional measurements of the surface ices. This could determine whether the surface ice, presumably in nearly the same state as it was when the primordial oceans froze, is significantly enhanced in methane relative to ammonia. This could determine whether the global ocean played a significant role in the formation of the atmosphere.

5: Conclusions

Titan and its atmosphere have been well studied, especially since the early 1970's and the Voyager missions. Since Voyager, there has been significant progress in the understanding of Titan's atmosphere, and there have been several possible explanations for its formation. Currently, the most favored hypothesis on the origin of Titan's atmosphere is the outgassing and volcanism theory, where the atmosphere formed from clathrates either on the surface or in the core of Titan, during or immediately after the accretion phase when Titan was still warm. However, it will not be possible to distinguish between these two theories until we can make measure the composition of the atmosphere and surface. The Huygens probe may be able to make this measurement, and answer the question of how Titan's atmosphere originated.


S. Engel and J.I. Lunine, 1994, "Silicate interactions with ammonia-water fluids on early Titan," Journal of Geophysical Research, vol. 99, no. E2, 3745
D.M. Hunten et al., 1984, "Titan," in Saturn, University of Arizona Press, 671
T.D. Jones and J.S. Lewis, 1987, "Estimated impact shock production of N2 and organic compounds on early Titan," Icarus, 72, 381
G.P. Kuiper, 1944, "Titan: a Satellite with an Atmosphere," Astrophysical Journal, 100, 378
J.I. Lunine and D.J. Stevenson, 1987, "Clathrate and ammonia hydrates at high pressure - Application to the origin of methane on Titan," Icarus, 70, 61L
C.P. McKay et al., 1988, "High-temperature shock formation of N2 and organics on primordial Titan," Nature, 332, 520
T. Owen, 1982 "The composition and origin of Titan's atmosphere," Planetary and Space Science, 30, 833
R.G. Prinn and B. Fegley Jr., 1981, "Kinetic inhibition of CO and N2 reduction in circumplanetary nebulae - Implications for satellite composition," Astrophysical Journal, 249, 308

(There are two figures which I obviously can't include, and both are just pie slices showing the radial structure of Titan at the time of accretion - undifferentiated rock and ice in the core, a rocky mantle, and a clathrate crust possibly with an ocean beneath the icy surface layer. The (possible) oceans and volcanism have long since frozen.)

In the Warhammer 40k universe, Titans are monstrous humanoid war machines, each standing over 100 feet tall. They originally appeared in games workshop's Adeptus Titanicus wargame, released in the late 1980's, and have been a major feature of the various incarnations of the epic game ever since. They are one of the things which show the scale and depth of the warhammer 40k universe; they are a minor feature relative to, for example, the space marines, but still show a great deal of thought, imagination and originality. They are unique in style, and vary massively between races, some hinting at the military functionality of battlemechs, while others are closer to the futuristic technology of the typical japanese mecha, or even have a steampunk feel.

Each Titan is an awesome war machine; easily capable of levelling buildings with a single blast of its fearsome weapons, or crushing the most powerful tanks underfoot like insects. They are protected by powerful and exotic energy fields, some have advanced holographic camouflage, and all have metres of heavy armour, making them impervious to all but the heaviest fire. All of the major forces in the 40k universe have Titans of some sort, which vary widely in design philosophy and capability, from the heavy machinery of Imperial Titans to the deadly grace of the Eldar (i.e. Elf) equivalents.

See also:

Compiled overview of the 100 ton Titan 'Mech, from various BattleTech novels and game sourcebooks:

Vining Engineering and Salvage Team designed and developed the Titan (or Grand Titan in the Federated Commonwealth). Building on the success of their much lighter Jackal design, VEST sought to diversify by creating the Titan as their entry to the assault 'Mech class. During the initial trial runs of the prototype, the Titan challenged an Atlas as a test of firepower and endurance . The battle lasted ten minutes, and the Atlas was left a charred hulk. The memorable scene of the Titan stomping on the skull-like head of its felled opponent is still used as a sales promotion tool for the Titan.

Assault 'Mechs are not known for speed, but the Titan moves fast enough to get into and out of trouble spots and still carries sufficient fire power to damage or eliminate the opposition. The key to this remarkable speed is the modified LTV 400 XL fusion reactor. This power plant suffered design problems in the early stages of development, but with those problems now resolved, the LTV 400 XL series has proven very reliable.

The Titan's defensive capabilities begin at the core, The 'Mech's skeleton is Corean Model 101BLP Endo Steel. More than 18 tons of Durallex Heavy Armor protect the internal mechanisms, enough in most areas to withstand even the deadly firepower of the Clan's OmniMechs. The VEST engineers incorporated the McArthur anti-missile system, giving the Titan additional defense against long-range missile attacks and double heat sinks permit the Titan to stay in action longer than its predecessors.

The Titan's offensive capabilities strike fear into the heart of even the most experienced MechWarrior. Each side of the 'Mech's right arm mounts a Diverse Optics Type 20 large pulse laser, supported by a standard Holly long range missile battery of 15 launch tubes equipped with an Artemis IV fire-control system.

The Titan is equally menacing at short ranges. Using the Artemis IV FCS, the Titan carries a Holly short-range missile six-pack in both the right and left torsos. Two Diverse Optics medium pulse lasers increase the medium and short-range fighting capability.

As a last-resort weapon, the Titan also mounts two Holly Streak SRM packs, one-shot firing tubes mounted on the upper shoulders of the Titan near the "neck". Pilots often use these tubes for point blank firing. The lead VEST engineer on the Titan project, David Courtney Vining, also mounted rear-fire capabilities in response to the new threat of Elementals on the battlefield. Two aft-firing Diverse Optics Small Pulse Lasers on the rear left and right torsos discourage close assaults.

The market was ripe for the Titan, and all the major Houses purchased the new 'Mech from Earthwerks. House Marik's Free Worlds League bought the majority of the supply.

Note: Information used here was the domain of FASA before they split the rights between Wizkids LLC and Microsoft (table-top gaming and video games respectively). Copyright of the fluff text is in limbo, but names of persons, places, & things are without any doubt the property of Wizkids LLC. Use of any terms here related to the BattleTech trademark are not meant as a challenge to Wizkids LLC's rights.

Author: John Varley
ISBN: 0441813046
Paperback: 320 pages
Publisher: Ace Books
Genre: Science Fiction

Spoiler-Safe Story Synopsis

Of Saturn, there can be said many things. For example, it's very far away from Earth, it has funny rings going around it, and it has an amazing amount of satellites spinning around it. One of them grabs the attention of the crew of the Ringmaster, a ship under the command of one Cirocco Jones (she likes her friends to call her "Rocky") -- a new moon, one never seen before.

Of course, on the onset it doesn't appear to be much at all. A couple kilometers across, looks a bit like a captured asteroid, but it's proximity to the equatorial plane makes it highly likely to be a new moon. A new moon with an agenda. After all, how many planetary bodies in the Solar System are actually alive?

Titan is the first of the three books in the Gaean Trilogy by John Varley, and serves many purposes, all done with remarkable skill. First, it introduces the characters that the reader will be interacting with throughout the length of the series (after reading the first, it's expected that you'll be so very into it that you want to read the next two). You meet Cirocco "Rocky" Jones; her on-again, off-again lesbian lover Gaby Plauget; the bizarre test-tube twins, April & August Polo (Cirocco knew for a fact that "what the Polo sisters did behind the closed doors of their adjoining rooms was still illegal in Alabama"); Calvin Greene, the black doctor who constantly reminds everyone of those two attributes; Bill (last name is never given), Rocky's ever trustworthy engineer-cum-lover; and Eugene "Gene" Springfield (last name actually not given until Demon, book three) who slowly goes insane.

Right, now, you've met the humans. Of course, on Titan, later called Gaea, there are other species. And the crew of the DSV Ringmaster figure this out when, for reasons unknown at the time, the "moon" attacks the ship and consumes it. The crew is belched up through sphincter-like holes in the ground, their space suits and uniforms reduced to only the metal parts, such as neck rings, radios, and wrist guards. On this lush, green planet (actually shaped like a wheel, with six spokes) with 1/6th the gravity of Earth, the crew finds themselves separated, hungry, disoriented, and ... changed somehow. They each felt different in unique ways. Cirocco suddenly concerned with leadership. Gaby her sidekick. Bill the dutiful man. Gene, the arch nemesis. Calvin the intellectual. The Polo sisters the mysterious aliens. It sounds remarkably like a cut-and-paste science fiction plot, yes? Well, sorta...

Heck, Cirocco and Calvin both wake up able to speak the language of two different species. Cirocco learns to sing the language of the half-horse, half-people mythical creatures roaming in Hyperion (one of the many zones of Gaea), and Calvin learns to whistle to the blimps, Brobdingnagian creatures who float in the sky throughout the world.

The planet is teaming with life. Titanides, a wonderful centaur-like race, obsessed with the works of Sousa, great sand worms in the desert ala Dune, and myriad other strange beasts. It seems like the planet itself has been manufacturing things heard on radio transmissions up to a hundred years old. Turns out that's precisely what she's done, for the planet is quite alive, and she's quite bored -- and a bored god is an insane god. She'd love to meet a few good heroes.

The writing style of Titan is very easy to comprehend, each new technical aspect described in calm detail. It would be easy to get bogged down in the aspects of describing a brand new world, but Varley handles it well, describing each new aspect as it comes up in terms the reader can understand. Occasionally, he becomes a bit long winded -- for example, the Titanides have a strange way of reproducing requiring at least one and as many as four parents. Varley dwells on this a great deal throughout this and the next two books, even so much as providing a diagram at the back of the book explaining all of the possible Titanide reproductive ensembles.

But no one can attack his creativity, particularly when it comes to the half-horse, single- and dual-gendered Titanides and their culture, as well as the individual cultures of the other species met in the book. He goes into amazing detail on each one. Out of four broken-then-taped-in-the-middle-glasses, I give it Π. Excellent introduction to a splendid series (which gets 3.8 out of 4, but that's a different node.

The Gaean Trilogy
Titan | Wizard | Demon

Written for The Bookworm Turns: An Everything Literary Quest.

Titan's thick atmosphere has long kept it a mystery to scientists, who could only guess at the nature of its planetary surface. The sixth moon of Saturn is the second largest moon in the Solar System, 50% larger than Earth's Moon1, but little was known about it until the Cassini mission entered Saturn's orbit in 2004. The Huygens probe (also known as Cassini-Huygens) finally landed on the moon's surface on 14 January, 2005. This node will look at Cassini's mission to explore Titan in some detail, and will then look at our current state of knowledge following its initial findings.

The Cassini Orbiter

Cassini-Huygens is a joint NASA/ESA/ASI (Italian Space Agency) mission. The 5.6 tonne spacecraft used the gravity of Venus, Earth, and Jupiter in a series of fly-bys following its launch in 15th October 1997, at Cape Canaveral. Cassini's objectives2 are to examine Saturn's rings, atmosphere, magnetosphere, and satellites, with particular emphasis on Iapetus and Titan. It therefore carries a barrage of scientific instruments, as well as the Huygens probe. One of the highlights of the mission, of course, was the successful launch and touchdown of the Huygens probe to the surface of Titan.

The Huygens Probe

The probe was named after Christiaan Huygens, Titan's discoverer, and left the orbiter on 25 December 2004, before descending to Titan's surface by parachute, and landing on 14 January 2005. During its descent, Huygens took many spectacular photographs, showing panoramic views of the moon as it descended. It also transmitted data continuously to Cassini by radio, which was in turn transmitted to Earth.

The Huygens photographs showed pale hills, probably of water ice, and dark "rivers" which appeared to flow to a dark plain. The probe landed on the plain which was covered in small rocks and pebbles made of water ice3.

The Surface of Titan

Cassini's first observations of Titan's surface showed a fairly smooth surface, with patches of bright and dark terrain3. Only three impact craters have been found, the largest being the 440-km wide Menrva impact basin. Other circular features appear to be filled in, perhaps by windblown sediment, raining hydrocarbons, or volcanoes. Volcanoes are also responsible for spewing water and ammonia into Titan's atmosphere.3.It has long been speculated that Titan might have seas or lakes of hydrocarbons such as ethane or methane, although some areas of dark terrain have now been found to be sand dunes4,5. We will now look at the evidence for mountains and seas or lakes on Titan.

Seas on Titan?

Cassini's radar has shown several areas of smooth reflections, thought to be lakes and seas of liquid ethane and/or methane. Evaporation from these lakes would help explain the high levels of methane in Titan's atmosphere. One sea covers an area of over 100,000 square kilometres (larger than Lake Superior). More examination is necessary to confirm the liquid nature of these lakes and seas.


Cassini's radar has also shown the presence of mountains and mountain ranges, some ranges as long as 150 km, and up to 1500 km high6. Some mountains seem to have been formed by tectonic forces such as compression of Titan's brittle lithosphere. Others may have been ejected by meteorite impacts or volcanoes7, and still others may have been formed by tectonic plates pulling apart, allowing material to well up from below.


Titan's thick atmosphere is the only developed atmosphere on any known moon in the Solar System, and is denser than that of the Earth. Its surface pressure is more than 1.5 times that of the Earth. The thick cloud layer prevents direct observation of the surface from Earth, and helps lower the moon's temperature by reflecting sunlight3.

Titan's atmosphere is 98.4% nitrogen, not unlike the Earth (78%), the remainder being mainly methane and other gases, including hydrocarbons.


The chemical make-up of Titan's atmosphere, and the possibility of liquid seas, make it a possible habitat for life, either now or in the future. It has been aruged that conditions on Titan are similar to conditions on early Earth, and that chemical evolution on Titan might yet lead to life on the moon. The possibility of liquid water or ammonia would increase the chances for life. It is also possible that microbial life might have travelled to Titan following asteroid and comet impacts on Earth. Titan is therefore seen as one of two possible harbours for life in the Solar System, along with Europa.



Ti"tan (?), a.


The Titan physical difficulties of his enterprise. I. Taylor.


© Webster 1913.

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