Notable features in the Sirenum Fossae region of Mars.

There are three notable features in this image of the Sirenum Fossae region of Mars. The image shows the region centred at about 28°S / 185°E. The largest impact crater in box 1 is around 50 km in diameter, and indicates that this region is ancient because such large craters rarely formed in more recent times. There is a large valley system in box two, and two parallel lines to the left-hand side of the box. These form a graben.

The central impact crater in box 3 has a diameter of about 28 km, and is relatively young because its centre remains jagged rather than having been smoothed by erosion. The youngest crater is the small 9 km-diameter crater. The crater at the bottom of the box is 34 km across, and the largest crater in the box, at 56 km diameter, is the oldest and most eroded.