The scene met by the Huygens Probe on Titan (left), and polished rocks from a river bed on Earth. Image credit Nasa
18th May 2010
Imagine looking up at our Moon with a telescope and not seeing the barren, dusty place pummeled by craters we all know so well…but a moon with an atmosphere, rivers, vast lakes, rain, wind, clouds, and even tides…dream on!! We don’t have that but Saturn does, in the shape of it’s incredible moon Titan. Titan even has a huge continent about the size of Australia, called Xanadu which appears very bright and reflective. Titan has erosion just like on Earth, but the materials used are different than Earth. Titan has the methane cycle instead of the water cycle, and an ice landscape of hills, valleys and plateaus, equivalent to the rocky landscapes of Earth.
The image above (left) shows the scene met by the European Space Agency’s Huygens probe when it landed on Titan in January 2005. The image on the right (credit: amateur photographer Sandra M. Matheson) shows rocks on a dry river bed on Earth, ground smooth by the action of water. The Titan image could also be a scene from Earth because both images show the same thing…a river bed. Although in the Titan image the “rocks” are round cobbles of water ice at around -180 degrees Celsius, ground smooth by the action of liquid methane and the friction of them grinding together.
But new data from Nasa’s Cassini Spacecraft has suggested what appears to be river channels on lowland areas of Xanadu, strewn with thousands of balls of ice from flash floods. The polished ice “rocks” range from a few centimetres up to a few metres in diameter, and have been transported at around 2 miles per hour, hundreds of miles downstream to end up tightly packed together. To the Cassini Spacecraft’s radar this scene is the brightest ever imaged on Titan, due to the reflective quality of the ice balls.
A 280 mile wide area on the edge of Xanadu showing a wide river channel. Image credit Nasa
The image above shows an area 280 miles across at Xanadu’s edge. It shows Xanadu at the top of the image as the brighter higher terrain, and a darker region south of it. A thick bright channel is flowing southwards out of Xanadu, and at some points measuring 3 miles wide. The ice balls probably originated as part of Xanadu’s bed rock, before they were polished smooth from flash floods caused by rain storms.
This is just one more example of just how Earth like Titan is. The same erosion and weather processes operate, but the elements involved are very different.
