Deep craters on the surface of Mars contain traces of clay that formed only in the presence of groundwater - this suggests that the red planet could have liquid water, and hence life, even after evaporation of its oceans, according to a paper published in the journal Nature Geoscience.

It is believed that on the surface of Mars in ancient times, in Noah's age (3.8 to 3.5 billion years ago), there were oceans and rivers of liquid water. Weight and dimensions of the red planet is too small to hold the large and dense atmosphere, causing the water gradually disappeared. Probe MRO (Mars Reconnaissance Orbiter) found in the second half of 2000-ies many deposits of clay, which is hidden inside a molecule of water. This discovery is considered evidence for the existence of water on ancient Mars, quoted an article RIA "Novosti".

A group of astrogeology under Joseph Michalski from the Institute of planetology in Tucson (Arizona) found evidence for the existence of water on Mars after the disappearance of surface waters by examining the properties of the deposits of clay some craters on the surface of the red planet.

In 2010 Michalski and his colleagues have found the first evidence for the existence of underground water reserves and the possible existence of life on ancient Mars, analyzing the data on the chemical composition of Martian rocks received by the probe MRO.

In the new work, the authors drew attention to the clay deposits are present at the bottom of a deep crater in the Martian McLaughlin "tropics" in the Northern hemisphere of Mars. Astrogeology noticed that these clays, according to the MRO, contained traces of salts of iron and magnesium. These substances can not be formed without the participation of the water molecules, which means "water" origin of the clays in the crater.

Michalsk? group suggested that the Martian clay could be due to the presence of large reserves of groundwater in surface and deep layers of the soil of the red planet. They tested this hypothesis using climate models, which describe the state of the soil of Mars in different geological era - during the relatively wet and warm Noah's age, and in the ensuing cold and dry Kaspereskey and Amazonicos ages.

The authors concluded that liquid water could exist on Mars, under certain conditions, at a depth of 2-5 km for a very long time, over billions of years, until the temperature of the planet's interior. According to Michalski and his colleagues, in the Martian soil conditions were quite favorable from the point of view of acidity, temperature and saturation of trace elements for the development of bacteria.

Following this idea, the researchers suggest the following to send the Rover into one of the deep craters where the asteroid impact could expose those parts of the soil, which once existed life. For example, the depth of the crater McLaughlin - 2 kilometers - can comfortably explore the traces of water and life, which can be hidden in deposits of clay at the bottom.