What are the features of the crater?
The crater has a diameter of about 45 kilometres and its heavily eroded rim is penetrated in the west and east by an inflow and outflow channel respectively. Such lakes are called "open basin lakes", which means that water continuously flows in and out of them. They are also fed mainly by surface water.
The sediments transported by the western tributary created a river delta whose mineralogical composition attracted the attention of the scientists: It consists not only, as so often elsewhere on Mars, of clay minerals rich in aluminium and iron and magnesium, which were formed by the chemical weathering of the source rock in the presence of liquid water. It also contains carbonate minerals that are common on Earth in limestone or dolomite and could actually have been formed in the lake itself. The interesting thing about these carbonate minerals formed in the lake is that they are particularly capable of preserving macro- and microscopic biosignatures, i.e. organic molecules or even fossil microorganisms, over billions of years.
The NASA mission Mars 2020 will use intensive and complex chemical investigations and sampling to investigate whether life once originated in this crater lake. In addition, 43 rock and soil samples will be deposited in containers that are to be brought back to earth by the early 2030s for precise analysis.