In the deep craters on the surface of Mars are signs of clay, the formation of which is due only to the presence of ground water - this is evidence of possible existence on Mars of liquid water, and therefore life, even after its oceans evaporated, according to a paper published in the edition of Nature Geoscience.
It is estimated that 3.8-3.5 billion years ago on Mars existed in the oceans and rivers, consisting of liquid water. In order to keep a large and dense atmosphere weight and dimensions of the Red Planet are very small, so the water gradually disappeared. In the second half of the 2000s, the probe MRO (Mars Reconnaissance Orbiter) found many clay deposits with hidden inside the water molecules. This discovery is regarded as evidence for the existence of water on ancient Mars.
Astrogeologov group led by Joseph Michalski of the Planetary Science Institute in Tucson (Arizona) have found evidence of water on Mars after the disappearance of surface water, having studied in detail the properties of clay deposits of clay in some of the craters of the Red Planet.
Michalski and his colleagues found back in 2010, the first evidence of the existence of groundwater and the possible existence of life on ancient Mars, following the analysis of the data obtained by the chemical composition of Martian rocks MRO probe.
The authors drew attention to the new work on the clay deposits that are at the bottom of a deep crater McLaughlin, located in Mars ’tropics’ in the northern hemisphere of the planet. Astrogeologi noticed that these clays contain traces of iron and magnesium salts, according to the MRO. The formation of these substances without the water molecules can not, indicating that the "water" origin clays crater.
By the assumption of Michalski, Martian clay could occur due to high volume of ground water in the surface and in the deep layers of the soil of the Red Planet. Researchers tested this hypothesis by applying climate model that described the condition of the soil of the planet during its different geological eras - a relatively wet and warm Noah’s age, as well as cold and dry, and Gesperiyskoy Amazoniyskoy eras that followed it.
The authors concluded that liquid water on Mars could be a very long time under certain conditions, at a depth of 2.5 kilometers, over several billion years, until cool subsurface of Mars. Conditions in the Martian soil, according to Michalski and his colleagues were quite favorable for the development of a variety of bacteria in terms of temperature, acidity and richness in trace elements.
Guided by this information, scientists are going to send another rover in one of the deep craters, which could open the asteroid impact of the soil, where once there was life. McLaughlin crater depth, for example, is two kilometers that allows to study traces of life and water, which may be hidden in the clay sediments, as well as its bottom.