ESA’s Mars Express space probe photographed a part of the region of Mars called Reull Vallis with its High Resolution Stereo Camera (HRSC). The photographed structure looks like a river and in fact it’s likely to have been formed when water flowed in the distant past.
This isn’t the first time that a spacecraft studies Reull Vallis: in 2009, NASA’s Mars Odyssey orbiter photographed it with its Thermal Emission Imaging System (THEMIS) camera and the Mars Reconnaissance Orbiter – another NASA’s space probe – photographed it with its High Resolution Imaging Science Experiment (HiRISE) camera. Even the Mars Express had already taken photos of the area in 2004, when it had just reached the red planet, and its HRSC allows to reveal details with up to 2 meters resolution.
This river has a length of about 1,500 km (about 932 miles) and can reach a width of about 7 km (about 4.3 miles) and a depth of about 300 meters (almost 1,000 feet). The Mars Express space probe’s HRSC has also revealed the existence of tributaries that added water to a river that in very ancient era had to be truly remarkable.
It’s estimated that tha one in Reull Vallis was a real river between 3.5 and 1.8 billion years ago. Later, the area was invaded by a glacier that dug the valley where there was the river pushing debris and ice creating the steep sides visible in the images taken by the Mars Express space probe.
Those are complex and diverse geological processes but they’re similar to those happened on Earth. Obviously, there’s a fundamental difference that on Mars at some point there was a huge climate change that turned it into what it looks like today.
According to scientists, the craters visible in the area close to the river were caused by relatively recent meteorite crashes. Those craters and other geological features of the area may contain a lot of ice water.
Those aren’t the first evidence that in the distant past Mars maybe was similar to the Earth and there was liquid water. However, places such as Reull Vallis are important to better understand the history of the red planet and improve our knowledge of geology and climatology. This is also important to better understand the great changes also occurred in the past on Earth and predict what will happen in the future.