The search for water on other planets is essential to classify them as potentially habitable, because where there is water there is also usually life (at least, as we know it).
During the last decade, several investigations, mainly from exploration instruments that collect information from the red planet, have suggested that not only was there water on Mars, but that it flowed in the form of rivers, and formed lakes. In 2015, NASA’s director of planetary science Jim Green announced at a press conference and in magazineNature Geosciencethe presence of salt water on Mars, and that this, in liquid form, was responsible for the linear grooves discovered on the slopes of craters during the hottest seasons of the red planet, thanks to data collected by the MRO probe (Mars Reconnaissance Orbiter) from NASA.
In 2020, other research, also published in the journal Nature Geoscience, showed that Mars likely received water from at least two very different sources in its earliest stage. Furthermore, in December 2019 we were informed that Mars had icy water just 2.5 cm from the surface.
Beyond the origin of the water on Mars, the fundamental thing is to know what state it is in today, and if it ever housed water in a liquid state. Now, new research comes to refute the belief that the red planet had liquid water on its surface. New evidence now suggests that valleys on the surface of Mars were carved by water melting under glacial ice. That isMars was once covered in ice, not liquid water; and that currently conserves part of that ice less than three centimeters from its surface, and at the poles.
As explained in the research, the geography of Mars was eroded by many processes, but liquid water does not appear to be one of them. The lead author of the research, Anna Grau Galofre, and her colleagues analyzed more than 10,000 morphological examples of Martian valleys in the form of algorithms. Their conclusions suggest that these morphologies were similar to those resulting from erosion of rivers or water in channels under ice sheets; but not by surface liquid water flows.
As cited in the study, these findings contradict previous interpretations of the geological record, which require precipitation and surface water runoff to form the valley networks. However, the new study indicates that ancient Mars was frozen, covered in ice, but not liquid water.
However, this does not mean that Mars did not host liquid water, but simply that this water did not flow on its surface.
Could it have been compatible with life?
An ice sheet covering a warm sea with liquid water can be conditions perfectly compatible with life. This is precisely the situation that the Earth went through in the remote past, some 250 million years ago, just before the Cambrian explosion of life.
In addition, other bodies in the solar system, such as the frozen moon Europa, is all of it a ball of ice under which it is estimated that there is an icy ocean, compatible with the existence of life forms.
