The outflow channels of Mars are huge! As the biggest of the Martian water-eroded channels, they stretch over several hundreds of kilometres, are ten to one-hundred kilometres wide, and are often at least a kilometre deep.
The Kasei Valles, one of the largest outflow channels on the planet, is itself about 1,580 kilometres long, and up to 480 kilometres wide. It may be two to three kilometres deep at certain locations. More than twenty outflow channels have been identified and named by scientists, and most of them are concentrated around major volcanic plains of Mars.
However, it is not their massive size alone that differentiates outflow channels from valley networks and gullies (the other Martian channel types) but also in their structure. The beds of these channels have streamlined islands, massive cataracts and terraces, and many other flow features typically associated with heavy flooding events.
Another speciality of outflow channels is that they are ancient formations! After studying the number of impact craters on their surface, scientists found that some of the oldest outflow channels on Mars may have formed as early as around 3.7 billion years ago. There are also certain other channels in the Elysium and Amazonis areas of Mars that are very old.
Picture Credit : Google
