There is a vast reserve of liquid water trapped between the cracks in the rocks deep beneath the surface of Mars, between 11.5km and 20km beneath the surface of the red planet. The discovery comes from a recent analysis of data collected by the Landing Insight of NASA, responsible for studying the internal structure of Mars through the analysis of the propagation of seismic waves. However, this is a deposit that is practically inaccessible with current technology, but it is interesting from an astrobiological point of view because it could in principle host any microorganisms. Before this discovery, water on Mars had been detected in the form of ice, traces of water vapor in the atmosphere, and in liquid form under the planet’s south polar ice cap.
Where is the Liquid Water Discovered Deep on Mars?
The lander Insight NASA’s spacecraft landed on the red planet in 2018, collecting data for as long as 4 years until the end of its mission in 2022. The mass of data collected is still being analyzed, which is why the conclusions of this new study have comeonly after a couple of yearsThe researchers analyzed data from the seismograph on board of the probe, which during its mission recorded well 1319 Martian earthquakes.
The researchers discovered that, at least at the location where the probe landed, there is a large reservoir of liquid water in the Martian subsurface. This water is found in the intermediate crust Martian, at a depth that within the margins of measurement errors should be between 11.5 and 20 km beneath the surface.
In particular, the data are consistent with a model that assumes the presence of igneous rocks (formed following the solidification of magma) fractured and saturated with liquid water. A vast underground ocean therefore does not appear to be the best explanation for the probe’s data.
The Insight spacecraft has only been able to record seismic data from the crust directly beneath its mechanical feet, but researchers expect there to be more similar reservoirs across the planet. If this were the case, there would be enough liquid water on Mars to form a layer on the surface more than 800 meters deep.
What the presence of liquid water on the planet could mean
The presence of water in liquid form is a basic requirement for life as we understand it on Earth, consequently this discovery points towards all those hypotheses that predict that, if life forms were they to still exist on Mars, they would be found in the undergroundshielded from the inhospitable conditions of the Martian surface.
Although we often hear about water on Mars, this research represents the first reliable case of detection of liquid water on Mars. In fact, the presence of water in frozen form in the caps of Mars, or in vwater vapor in the atmospherebut never in liquid form.
This study also explains what happened to all the liquid water that we know flowed on the surface of Mars more than 3 billion years ago. Part of it evaporated and was dispersed into space due to the loss of atmosphere of Mars due to its low gravity and lack of magnetic field. But the remaining part seems to have been trapped undergroundwho knows, perhaps in the company of alien life forms.
How do we know that the water found underground on Mars is liquid?
The discovery of liquid water in the Martian subsurface was possible thanks to the analysis of data produced by seismographs on board of Insight, which during the operational life of the probe have recorded 1319 earthquakes. Seismic waves, in fact, move with different speeds depending on the physical characteristics of the vehicle in which they propagate.
By modeling the characteristics of the Martian subsurface in terms of density and composition, scientists have created various models with different values for example of the density of the material, its porosity or chemical composition. The measured data were then compared with these models, finding that the one that best explains the data is consistent with igneous rocks saturated with liquid water.
The technique of using seismographs to map the subsoil is not new, but it is also widely used on Earth, to search for water or to search for oil and gas. Consequently, it is a very reliable technique, although the uncertainty about the characteristics of the Martian subsoil is greater than that we have of the terrestrial subsoil, since we can actively excavate the latter.
