Titan, Saturn's largest moon
Titan is the largest moon of Saturn, the second largest in the Solar System (after Ganymede of Jupiter). It was discovered by Christiaan Huygens in 1655.
Titan's rotation period of about 16 days is synchronous to Saturn (meaning the same side always faces Saturn). It is the only moon in the Solar System known to have clouds and a thick, planet-like atmosphere.
Distance from Saturn
1 221 870 km
Distance from Sun
1 427 000 000 km (9.54 AU)
Diameter (atmosphere)
5550 km
Diameter (surface)
5150 km
Mass
1/45 that of Earth
Average density
1.881 times liquid water
Surface temperature
94K (-180 degrees C)
Atmospheric pressure at surface
1500 mbar (1.5 times Earth's)
Atmospheric composition
Nitrogen, methane, traces of ammonia, argon, ethane
Orbital period (Titanic day)
15.95 Earth days
Titan’s atmosphere
NASA's Voyager 1 provided the first detailed images of Titan in 1980. They showed only an opaque, orange atmosphere, apparently homogeneous.
It was so thick that you could not see the surface. However, other data revealed exciting things. Similarly to Earth, Titan's atmosphere is mostly nitrogen but there is also methane and many other organic compounds.
Before the arrival of the ESA Huygens probe, planned for January 2005, astronomers will observe Titan using the most powerful ground-based telescopes.
Titan's murky atmosphere with the Huygens probe descending on the left
Images from the WM Keck Observatory reveal methane-containing clouds near Titan's south pole. This could mean that Titan has the equivalent of a weather cycle similar to ours on Earth.
This is a major discovery which means that the atmosphere is much more dynamic than previously thought.
The NASA Cassini orbiter will clearly see these clouds, carrying out precise observations before, during and after releasing the Huygens probe.
First view of Titan from Cassini-Huygens
Titan’s surface
Over the years, scientists have dramatically changed their minds about Titan's surface. In the 1990s, the NASA/ESA Hubble Space Telescope spied an area on Titan that was brighter than the rest.
More recent observations show the same feature better. What are these bright and dark patches? Some scientists believe the bright area could be a continent and the rest oceans, but no one knows for sure, yet.
The recently discovered large continent-sized feature (red) is called Xanadu. It is unclear whether Xanadu is a mountain range, a giant basin, a smooth plain or a combination of all three. It may be dotted with hydrocarbon lakes but that is also unknown.
All that is presently known is that in Earth-based images, it is the brightest region on Titan. There is no doubt, though, that the surface appears very diverse, not uniform. There are a lot of surprises waiting for us there.
Where will Huygens land? ESA scientists predict the probe will land close to the bright patch, but not on it. This could be a landing in an ocean - which would be the first splashdown landing in an ocean off the Earth!
To land on an ocean would probably mean better data from Huygens. Even if the probe lasted only a few minutes before sinking, it would at least stay in an upright position. Being the right way up is essential for sending the data back to the Cassini orbiter and to the scientists on Earth.
Moreover, some of Huygens's instruments are better prepared to analyse liquids. If Huygens lands on a solid surface instead, there is a higher risk of falling in the wrong direction and not being able to easily communicate with Cassini.
Life on Titan
Will Huygens land or splashdown on Titan?
Titan, Saturn's largest moon, is a mysterious place. Its thick atmosphere is rich in organic compounds. Some of them would be signs of life if they were on our planet.
How do they form on Titan? Will they help us to discover how life began on Earth?
Titan's atmosphere is mostly nitrogen but there are also methane and many other organic compounds. Organic compounds form when sunlight destroys methane. If sunlight is continuously destroying methane, how is methane getting into the atmosphere?
On Earth today, it is life itself that refreshes the methane supply. Methane is a by-product of the metabolism of many organisms. On Earth, the simplest biological sources, such as those associated with peat bogs, rice fields and ruminant animals, continuously supply fresh gas to replace that destroyed by oxidation. Could this mean there is life on Titan?
Titan is not a pleasant place for life. It is far too cold for liquid water to exist, and all known forms of life need liquid water. Titan's surface is -180°C. According to one exotic theory, long ago, the impact of a meteorite, for example, might have provided enough heat to liquify water for perhaps a few hundred or thousand years.
However, it is unlikely that Titan is a site for life today. But scientists are still currently puzzled by the amount of methane that persists in Titan's atmosphere. Could there be oceans of methane on or under the surface?
http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens/Facts_about_Titan
Titan: Overview
Titan is Saturn's largest moon. It is surrounded by a thick, golden haze, and only certain kinds of telescopes and cameras can see through the haze to the surface. Titan is of great interest to scientists because it has flowing liquids on its surface and a dense, complex atmosphere.
10 Need-To-Know Things About Titan
- If the sun were as tall as a typical front door, Earth would be the size of a nickel and Titan would be the size of a pea.
- Titan is a moon that orbits the planet Saturn. Saturn is the sixth planet from the sun at a distance of about 1.4 billion km (886 million miles) or 9.5 AU.
- One day on Titan (the time it takes for Titan to rotate or spin once) takes about 16 Earth days. The length of Titan's day is the same as the amount of time it takes Titan to orbit Saturn. Saturn makes a complete orbit around the sun (one Saturn year) in about 29 Earth years (10,759 Earth days).
- Like many other moons (including Earth's moon), Titan is locked by gravity to its planet so that the same side always faces toward Saturn.
- Titan has been called the most earthlike world in the solar system because it has lakes, seas and flowing rivers on its surface, although the liquid is methane (CH4) and ethane (C2H6) instead of water.
- Like Earth, Titan's atmosphere is mostly nitrogen (N2). It also contains small amounts of methane and other complex hydrocarbons. Titan's atmosphere is slightly denser than Earth's.
- Titan does not have rings. Its gravity helps to shape ringlets, gaps and other structures in Saturn's rings.
- Titan has been visited by two spacecraft and one surface lander. Voyager 2 made the first flyby of Titan in 1980. The Cassini spacecraft has made scores of flybys of Titan since 2004. The Huygens probe, carried to Saturn by Cassini, parachuted to the surface in 2005.
- Scientists who study living things do not think life as we know it is likely on Titan's surface. Some scientists think Titan's subsurface ocean might contain a habitable environment.
- Seas on Titan are named for mythical sea monsters, while its mountains are named for mountains found in the works of author J.R.R. Tolkien.
Titan is the biggest of 53 confirmed moons orbiting Saturn (another 9 moons are being confirmed). Titan is a frigid world enveloped by a thick, hazy atmosphere that obscures its surface. Titan has been studied in great detail only in the past few years, with the arrival of the Cassini-Huygens mission at Saturn in 2004.
Titan is the second largest moon in our solar system, with an equatorial radius of 2,575 km (1,600 miles). It is bigger than Earth's moon, and even larger than the planet Mercury.
Only Jupiter's moon Ganymede is larger than Titan, with a diameter barely 112 km (62 miles) greater.
The temperature at Titan's surface is about -178 degrees Celsius (-289 degrees Fahrenheit). At this frigid temperature, water ice is as hard as rock - in fact, most of the rock on Titan's surface is water ice.
Titan orbits Saturn at a distance of about 1.2 million km (745,000 miles), taking almost 16 days to complete a full orbit.
Titan is of great interest to scientists because it is the only other place in the solar system known to have an earthlike cycle of liquids flowing across its surface. That Titan has seas of liquid methane was suspected before the first spacecraft flyby, but its opaque atmosphere prevented close inspection even then. In 1980, NASA's Voyager 1 spacecraft tried to take close up images of the natural features of Titan's landscape, but was unable to penetrate the thick clouds. Instead, the images showed only slight color and brightness variations in the atmosphere. Titan's atmospheric pressure is about 60 percent greater than Earth's -- roughly the same pressure found at the bottom of a swimming pool.
In 1994, NASA's Hubble Space Telescope recorded pictures of Titan, which suggested that a huge bright continent exists on the hemisphere that faces forward in orbit. These Hubble results didn't prove that liquid seas existed, however; only that Titan has large bright and dark regions on its surface.
NASA's Cassini spacecraft (currently orbiting Saturn) has finally revealed the mysterious moon's true nature. Cassini was specially designed to peer through Titan's haze with radar and in certain colors of light, called spectral windows, that allow a glimpse of what lies below. During dozens of flybys, the Cassini orbiter has mapped a large fraction of Titan's surface and made detailed studies of its atmosphere. Cassini also carried the European-built Huygens probe, which parachuted through Titan's atmosphere in 2005 to make the first landing on a body in the outer solar system.
From Cassini-Huygens, we now know that Titan has lakes and seas of liquid methane (natural gas) and ethane near its poles. These bodies of standing liquids appear to grow and shrink in a seasonal cycle as storms bring rain to one hemisphere, then the other. The mission has revealed drainage channels on the surface that were carved by flowing liquid.
Cassini's radar instrument revealed that large swaths of the surface near the equator are blanketed by dune fields, similar to the Namibian desert on Earth. The mission has also found that Titan has an internal ocean of liquid water.
Because of the extremely cold temperatures at Titan's distance from the sun, chemical processes take longer to unfold, leaving the chemistry of the moon's atmosphere in a state of deep freeze. This carbon-rich chemistry is of great interest to scientists because it could be similar to the atmosphere of early Earth, before life emerged on our planet.
Discovery:
Titan was discovered on 25 March 1655 by the Dutch astronomer Christiaan Huygens.
How Titan Got its Name:
The name Titan comes from a generic term for the children of Ouranos (Uranus) and Gaia in ancient Greek mythology. In the stories, the Titans were the ancestors of the human race. The Titans were known to have devoured the limbs of Dionysus, the son of Zeus. Enraged, Zeus struck the Titans with lightning. (Zeus had intended this child to have dominion over the world.) The lightning burned the Titans to ashes, and from the ashes, mankind was formed.
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Titan
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