This is a Mars Reconnaissance Orbiter view of hoodoos on Mars. The image is part of a larger image you can see here (links off-site)
I better let Candy Hansen (NASA/JPL/University of Arizona) explain: On Mars, we often see inverted river channels preserved perched above the surrounding terrain because the sediment inside the river channel was stronger than its surroundings. This is common in the American Southwest in places where lava flowed down river channels and the surrounding sandstone subsequently eroded away leaving ridges in places that started as valleys.
There’s another example of high-standing columns protected by a strong cap rock, called “hoodoos.” Looking closer at our image, we see what looks like a crater and its rays of ejecta, preserved and slightly higher than the surrounding terrain, possibly due to a similar process.
Image: NASA/JPL/University of Arizona