 Titan is Saturn's largest moon. It is one of only two moons in our solar system with an atmosphere; its atmosphere is very thick. Conditions on Titan are thought to resemble those on earth in its early history. Titan's diameter is just over 5000 kilometres, making it larger than Mercury, and larger and more massive than Pluto. Observations by the Hubble Space Telescope indicated that Titan's rotation is synchronous, just like our moon. In other words, its period of rotation is the same as its orbital period, so that the same side of Titan always faces Saturn. Because of its atmosphere, Titan is an interesting place ... the spacecraft Voyager 1 was directed to within 4000 km of its surface in order to find out more about this moon. But we still don't know much; its atmosphere is opaque, so we can't see the surface with visible light, although some details have been discerned using other frequencies. Scientists suspect that Titan is about half rock and half water ice. Its interior is probably hot, since the moon is so massive (gravitational compression causes warming). Its atmosphere is mostly nitrogen (as is Earth's), although the pressure at the surface is 50% higher. Trace amounts of organic compounds, such as carbon dioxide, methane, ethane, and hydrogen cyanide, have also been detected. There are scattered clouds in Titan's atmosphere, probably composed of methane, ethane or other simple organics. Other chemicals in small quantities must be responsible for the orange color of Titan. This mix of chemicals is similar to the conditions on Earth early in its history, when life was first getting started. This is the reason for the intense scientific interest in Titan. The Cassini spacecraft, which was launched in 1997, has already sent us spectacular pictures of Jupiter. This spacecraft also reached Saturn in early 2005. The Cassini spacecraft was one of the largest, heaviest, and most complex interplanetary spacecraft ever built. The orbiter alone weighed 2,150 kilograms. One of its major assignments was to map the surface of Titan with radar. We have some of those photos on our second page. 
It also dropped a probe into Titan's atmosphere. The probe, called Huygens after the discoverer of Titan, opened a parachute, allowing it to float to the surface. The landing site was near an ocean of liquid methane, as identified by the Hubble telescope.The painting shown here is an artist's interpretaion of how Saturn might look from the surface of Titan, after the Huygens probe had landed. For more information, go on to page two to see some results from the Huygens probe, and some actual photos, as well as more recent photos by Cassini of the surface of Titan. |