Pic of the Week: Martian Polygons

Image (Credit): (NASA/JPL-Caltech/University of Arizona)

This week’s image is from NASA’s Mars Reconnaissance Observer. The Martian surface looks magical as we see the effects of water and ice. We tend to see Mars in one way – the view from a lander or rover showing a plain desert-like horizon (shown below) – but from above we can see it is so much more.

NASA has this to say:

Both water and dry ice have a major role in sculpting Mars’ surface at high latitudes. Water ice frozen in the soil splits the ground into polygons. Erosion of the channels forming the boundaries of the polygons by dry ice sublimating in the spring adds plenty of twists and turns to them.

Spring activity is visible as the layer of translucent dry ice coating the surface develops vents that allow gas to escape. The gas carries along fine particles of material from the surface further eroding the channels. The particles drop to the surface in dark fan-shaped deposits. Sometimes the dark particles sink into the dry ice, leaving bright marks where the fans were originally deposited. Often the vent closes, then opens again, so we see two or more fans originating from the same spot but oriented in different directions as the wind changes.

Image (Credit): The view from NASA’s Mars Exploration Rover Opportunity showing a portion of the west rim of Endeavour crater. (NASA/JPL-Caltech/Cornell/ASU)