In this image from NASA's Mars Reconnaissance Orbiter, dark branching features can be seen on the floor of the Antoniadi crater. Their shape resembles that of giant ferns. The dark channels are filled with a rocky material which is harder than the surrounding sediment. As the softer sediment around the channels eroded away, the harder, rocky material was left behind to form the raised, fern-shaped features.
NASA / JPL-Caltech / University of Arizona
Solar System | Faces of Mars | Visions of Jupiter | Sights of Saturn
Best of Hubble #1 | Best of Hubble #2 | Spitzer Spectacles | Above the Earth