Rover missions allow us to explore Mars from close up, but we can also gather a great deal of information about the planet using orbiting spacecraft which can capture images of the planet as they move around it. The European Space Agency (ESA)’s Mars Express orbiter has been in orbit around the planet since 2003, collecting information using tools like high-definition cameras, radar sounding, and atmospheric analysis.
Now, the orbiter has captured an image of a part of the Martian surface with interesting geology, showing deep valleys and tall ridges formed by activity beneath the planet’s surface stretching and tearing the crust above it.
The orbiter captured this image of the Martian surface in the volcanic Tharsis province or Tharsis rise, close to the planet’s equator. It is part of the boundary region where the largely smooth and flat Northern hemisphere meets the mountainous and cratered Southern hemisphere.
The lines you can see across the image consist of two types of feature: Grabens and horsts, similar to ridges and valleys in that some areas protrude up above the surface and some sink down below. The structures are several kilometers wide and long, and are a few hundred meters deep.
You can also see that most of the structures run parallel to each other, but there are a few scratches running perpendicular to the others. These are caused by volcanic and tectonic activity in the Tharsis province, which hosts some of the largest volcanoes in the solar system. As the activity beneath the surface increased, it stretched the crust above it, creating the ridges. When the direction of the stress changed, it caused the perpendicular cracks to appear.
The ESA also produced this color-coded topographic view of the same region, with points of high altitude shown in red and yellow and points of low altitude shown in green and blue. You can see that on the top right of the image, it is considerably lower and flatter than the left side. This smoothness was caused by the flow of lava over the surface long ago, filling in depressions and leaving a smoother exterior.
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