Mars Express has revealed the first geological evidence of a system of ancient interconnected lakes that once lay deep beneath the surface of the Red Planet.
The new study reveals the extent of groundwater on Mars that previously only predicted by models. "We tracked this water in our study, as its scale and role is a matter of debate, and we found the first geological evidence of a groundwater system on the entire planet on Mars," says Francesco Salese, of the University of Utrecht, Netherlands.
Five of the lakes found contained signs of minerals related to the emergence of life on Earth, as well as clays, carbonates and silicates. Salese, along with his colleagues, explored 24 deep craters closed in the northern part of Mars, with floors about 4000 meters below the so-called Martian sea level (On Mars this level of the sea refers to atmospheric pressure and elevation due to the absence of the sea, in addition to being aligned with coastal lines of a supposed ocean that existed between three and four billion years ago). They found features in the floors of these craters that could only have formed in the presence of water. "The early years of Mars were an aquatic world, but as the climate of the planet changed, the water retreated below the surface to form pools and 'groundwater' ".
The history of water on Mars is complex, and intrinsically linked to understanding whether life arose there or not, and, if so, where, when and how it did it. The characteristics of these craters indicate that they once had puddles and water flows. These include channels carved into crater walls, valleys dug by groundwater, dark deltas and curves that are thought to have formed as water levels rose and fell, terraces dotted within the crater walls formed and deposits of Fan-shaped sediments associated with water flow.
"Finds like this are very important; help us identify the regions of Mars that are the most promising to find signs of past lives ", says Dmitri Titov, scientist of ESA's Mars Express project. The next mission will be launched next year. On the other hand, the ExoMarts Trace Gas Orbiter continues studying Mars. "It is especially exciting that a mission that has been so fruitful in the Red Planet, Mars Express, is now an instrument to help future missions like ExoMars to explore the planet in a different way. It is a great example of missions that work together with great success, "added Titov.