Photo Credit: NASA

Drainage Channels on the Planet Mars

The interplay of air and sand in “Braided Stream” suggests features on terrestrial planets formed by the forces that draw and oppose flowing material as it seeks the paths of least resistance, creating ever-changing channels and drainage networks.  These forces are responsible for some of the most stunning geological formations on Earth, Mars, and Venus, as well as on our Moon and on Jupiter’s moon Io.  

Photo Credit: NASA

Lava Channels on the Olympus Mons Volcano, Mars

The channels created by the flowing material--whether air, water, ice, lava, or other substances--are constantly forming and reforming in response to many factors.  Flows merge or split, finding new paths.  Sometimes flows become temporarily blocked and create chambers or lakes.

Continuous flow erodes the walls of a channel, allowing it to enter previously uncarved territory. Sometimes the walls collapse suddenly, dramatically altering the flow.

Erosion also occurs when the flow changes speed in response to an obstruction or bend.  Slower flow sustains pressure against the channel wall, working to keep it intact.  Swifter flow, by reducing that pressure, intensifies the wall’s erosion.  The interaction of flow and pressure is described by a law of flow dynamics called the Bernoulli Principle, which states that as a moving fluid’s speed increases, its pressure decreases.