In this section: Mars | Europa | TITAN Titan is the largest moon of Saturn, and the only moon in the Solar System with a dense atmosphere The atmosphere on Titan could be identical to that of the early Earth when life began The orange haze surrounding the globe could conceal carbon-rich lakes, oceans and storms of chemical rain. Could it also house life?

The Huygens Probe Artist's impression of the first probe on Titan In January 2005, the Huygens probe landed on Titan. It sent data for over two hours, including more than 300 images and a sound recording of the atmosphere. The data will keep scientists busy for years as they learn more about this fascinating place. See the first images from Titan on bbc.co.uk/news

Titan is a world very different to our home planet. It's cloaked in a thick orange haze, so the only way to discover what lies beneath the clouds is to pay a visit.

In January 2005, the Huygens probe landed on this mysterious moon. It sent back images of what looked like drainage channels leading into a dark lake or sea. Titan may be the only place, other than the Earth, that has liquid running across its surface. But instead of water, Titan's lakes would be made of liquid methane or ethane.

Black ethane rain may fall out of Titan's smoggy skies. These showers could trickle down to streams, rivers and oceans, with rolling waves larger and slower than on our own planet.

Harbouring all these carbon-rich molecules, Titan could be a very fertile place.

Discover the essential ingredients for life.

Was Titan like the early Earth?

Titan's atmosphere, like Earth's, is full of nitrogen. But it also has methane and traces of other organic molecules. So the recipe for Titan's atmosphere is very similar to the Earth's at the time when life began.

Learn more about how life began on Earth

But unlike the Earth, Titan is a cold world. At 1,200 million km (800 million miles) away from the Sun, the surface is a chilly -180ºC. Any water would be frozen solid. And chemical reactions would happen at a sluggish pace.

So the chances of life evolving on Titan today are very slim indeed. But this may not always have been the case...

Did Titan spawn life long ago?

Once upon a time, Titan may have been a lot warmer than today. Liquid water oceans may have flowed across its surface, breeding microscopic life. As the world began to freeze over, these life-forms could have survived beneath the surface.

However, any creatures living there now couldn't rely on the distant Sun for their energy supply. They'd have to feed entirely from the chemicals in Titan's ocean.

Artist's impression of a probe landing on the surface of Titan

Life may return in the future

Titan may be too cold for life now. But in several billion years time, our Sun will become a red giant, swelling to fifty times its current size. Then the temperature on Titan's surface will rise to a more hospitable -100ºC.

This should be warm enough to melt the frozen surface mixture of water and ammonia. So as the Earth becomes too hot to inhabit, Titan may start a whole new lease of life.

Learn more about the surface features on Titan