Reull Vallis in Mars’ southern hemisphere is believed to have been carved by water in the distant past. This section of channel is 4.3 miles across and 985 feet deep. A small tributary channel merges back into the main channel (above center). Linear features are clearly seen on the valley floor in this view, evidence of ice and loose debris scraping away the floor in a glacial-like manner. Click for larger version. Credit: ESA/DLR/FU Berlin (G. Neukum)

Here’s a photo to relish. Granted, the perspective was computer-generated, but it’s based on hard data obtained from the High-Resolution Stereo Camera on the European Space Agency’s Mars Express. Spectacular, isn’t it? The spacecraft has been in orbit about the Red Planet since Christmas Day 2003, snapping photos of features down to about 6 feet or the size of your refrigerator.

Original photo of Reull Vallis. Its sides are sharp and steep. Credit: ESA/DLR/FU Berlin (G. Neukum)

Reull (Ree-ul) Vallis, named for the Gaelic word for ‘planet’, was likely carved by flowing water in Mars’ ancient past between 3.5 and 1.8 billion years ago. The Reull flowed from a highland region across some 930 miles or rocky terrain before emptying onto the floor of the vast Hellas Basin, the planet’s largest impact crater. To appreciate its 4.3-mile width, consider that the Mississippi River is only about 1 mile wide at its broadest. Think of all the sediment this river must have dumped into Hellas during its lifetime.

Mars volcanoes Ceraunius Tholus and Uranius Tholus photographed by Mars Express. Although not active now, they were in the distant past. Click for a large,  3-D version. Credit: ESA/DLR/FU Berlin (G. Neukum)

In both the overhead and perspective views, you can see lots of roughly parallel grooves. They’re scrape marks believed to have formed when rocky debris and ice carried by glacial flows passed through the channel during more recent Amazonian Epoch.This period of Martian history began roughly 1.8 billion years ago and continues to the present day. It’s been characterized by lava flows, active Martian volcanoes, landslides and a lack of impact craters.

Signs of glacial ice flows in the 582-mile-wide feature Deuteronilus Mensae (doo-ter-0h-NEE-lis MEN-see). NASA’s Mars Reconnaissance Orbiter has detected thick ice under the red Martian dust here. Click to enlarge. Credit: ESA/DLR/FU Berlin (G. Neukum)

Ages are estimated for the varied landscapes on Mars and nearly every other solar system body by counting craters. The more craters, the older the terrain. Way back 4 billion years ago, there were far more errant asteroids and comets flying around than today. They pummeled EVERYTHING. Planets like the Earth and moons like Io and Titan have erased most of these early scars through erosion and volcanism. Less active worlds like the moon still carry their record of ancient bombardment.

Wanna see more striking images from Mars Express? Click HERE.