The Mars Express orbiter studying the Red Planet has revealed signs of massive trenches and valleys on Mars, similar to those caused by running water on our home planet. The vehicle, designed and managed by the European Space Agency (ESA), has recorded images of a river valley on the Red Planet, hinting at an ancient, wetter past on this alien landscape.
Mars is an arid place in the modern age, but long ago, the atmosphere was thicker, able to hold liquid water on its surface. The new images show evidence for vast volumes of running water in the southern highlands of the Red Planet.
“The topography of this region suggests that water flowed downhill from the north (right) to the south (left), carving out valleys up to two kilometres across and 200 metres deep as it did so. We see these valleys as they stand today, having undergone significant and heavy erosion since they were formed,” the ESA reports.
Erosion is seen as broken, smooth valley rims, where the flow of water erased the harsh edges of rocks and craters.
The formations seen by Mars Express are known as dendritic morphology — from the Greek word dendron, meaning tree. These formations are likely the result of surface water runoff from a powerful river, fed by extensive rainfall.
“Valley networks that criss-cross the southern highlands were also probably formed by water. And many craters, especially at high latitudes, are surrounded by fluidised ejecta resembling the ring of splattered debris around a stone dropped in soft mud. This suggests that there was underground water or ice in early times, and possibly more recently,” the ESA explains on the Mars Express website.
For Mars to have developed these surface features, the atmosphere of the planet must have once been significantly denser than what exists on that world today. Geological features showing evidence for water on the Red Planet are more than 3.8 billion years old.
The Mars Express was designed with seven instruments to answer the question of why Mars lost its water, and where it may now be hidden. Current thinking suggests the water may have been escaped into space, trapped underground, or both. Analysis of data from the Mars Reconnaissance Orbiter (MRO) reveals vast quantities of water ice, as much as 100 meters (330 feet) in depth, sitting just a few feet beneath the ruddy surface of the Red Planet. Researchers from the ESA also hope to better understand what caused Mars to lose its atmosphere, which is currently just one percent as thick as that on our home planet.
One of the greatest mysteries of Mars is whether a wetter, warmer climate in the distant past may have led to the evolution of life on the Red Planet.
In 2020, the ESA, together with the Russian space agency, Roscosmos, will launch the ExoMars landers to the Red Planet. This mission will include a rover, recently named after biologist Rosalind Franklin, which will explore the Martian surface, drilling into its surface for the first time ever. Meanwhile, a second stationary science vehicle will carry out experiments exploring the geology and chemistry of Mars.