Cienciaes.com: Is life possible in the ocean of Ganymede? We spoke with Fernando Izquierdo

2020-12-07 20:32:32

Ganymede is an unusual satellite of Jupiter, not only is it the largest in the Solar System, even larger than Mercury, but it is believed that it has a molten core, rich in iron, capable of generating a field inside it. magnetic, as it is here on Earth. From the outside, it shows a surface where bright and dark terrain riddled with craters alternates, but the most fascinating thing about Ganymede lies below the surface, between the core and the outer crust, there, according to scientists, there is a huge submerged ocean that houses so much water as contained in all the oceans on Earth. And, it is already known, an environment in which there is liquid water, energy and nutrients, the existence of life is possible. The difficult thing is to discover it.

A key issue in finding life in such an inaccessible place, such as the interior of Ganymede, consists in knowing as well as possible the physical and chemical conditions of the environment. An army of planetary physicists, chemists, and geologists are striving to understand what conditions are like in Ganymede’s subterranean liquid ocean, and they do so by studying the problem from many angles. One of them consists of observing it up close and better known, that is, the terrestrial environments that could be similar in some way to what happens there. If we descend to the depths of the Earth’s oceans, we observe that the water is at a low temperature, barely 4ºC, and the pressure is tremendous. Given that every 10 meters that we submerge under water, the pressure increases by one atmosphere, it is easy to calculate that at a depth of 5 kilometers the pressure is close to 500 atmospheres and if we descend to the deepest oceanic abysses the pressure doubles.

What will the environment be like inside Ganymede?

Our guest on Talking to Scientists, Fernando Izquierdo Ruiz, explains it in detail. Calculations indicate that the underground ocean of Ganymede is deeper than that of the Earth, it is believed that it can reach up to 100 kilometers, as a consequence, although the gravity is lower, the pressure is much higher than that which exists in the bottoms terrestrial. There the water is found between two layers of ice, one closer to the surface, where the cold outside prevails, and another in the depths, covering the rocky bottom, due to the enormous existing pressure. Now, for the existence of some kind of living organism, something more than liquid water is needed, energy is needed. It is thought that the internal heat of the satellite and the tidal forces of Jupiter are the factors that supply that energy. Finally, nutrients are necessary. Here on Earth, the organisms that live at the bottom feed on the substances dissolved by the contact of the water with the rocky bottom, a bottom that in the case of Ganymede is not in contact with the liquid water because the layer of rock prevents it. ice deposited on it, how would the exchange be possible then?

A possible solution to the problem of nutrients is the one proposed, in an article published in ACS Earth and Space Chemistry, Fernando Izquierdo, Manuel Recio and Olga Prieto Ballesteros. The team has investigated the behavior of certain substances, called CO2 hydrates clathrates, these are substances that, under certain conditions of low temperature and high pressure, create a crystalline network of water molecules in which cavities are formed that can house small molecules of other substances. On Earth, on the ocean floor, there are large deposits of methane clathrates and perhaps something similar happens on the ocean floor of Ganymede. Laboratory tests and simulations using quantum mechanical calculations have allowed researchers to conclude that the conditions prevailing in the subterranean oceanic seas of satellites such as Ganymede or Europa are ideal for the existence of CO2-storing clathrate hydrates. The experiments reveal that, under high pressures, CO2 could not only be trapped in the clathrate but, once formed, channels would be produced that would allow the exchange of substances between the rocky bottom and the liquid water. Thus the nutrients would pass into the inner ocean and could support some kind of life, if any.

These experiments open avenues of research that will allow us to discover how clathrates or gas hydrates could store molecules and other essential elements for life in places located beyond Earth, even if they are far from the so-called “habitable zone”, characterized by the possibility of existence of liquid water on the surface.

I invite you to listen to Fernando Izquierdo Ruiz, currently a researcher at Chalmers University of Technology, in Gothenburg, Sweden, whose research was carried out in the Theoretical and Computational Chemistry of Materials group (QTCMAT) of the Malta Consolider Network of the University of Oviedo and by the Center for Astrobiology (CAB, CSIC–WHILE).

Reference:
Theoretical Characterization of the High Pressure Nonclathrate CO2 Hydrate by F. Izquierdo-Ruiz, J. Manuel Recio and O. Prieto-Ballesteros.