Science

Is something moving in Europe?

A world crisis like the pandemic or Afghanistan jumps, or, worse, an internal crisis like the attitude of some countries with respect to human rights, and the European Union resembles the committee of the “Popular Front of Judea” in The life of Brian , discussing about passing motions to discuss motions about a motion to help fix the problem. One wonders if Europe is moving, if there is life in the institutions of the EU or of the member countries. But it is not from that Europe or from that political life that we are going to talk about today, this is not an open letter from Josep Borrell or a column from Cué.

In what should have been a cold night of January 8 of the year 1610, an Italian from 44 years (as far as we are concerned, we will say that the 40 are the best age to do things as) first observed something in the sky that revolutionized the world. And it took him to jail, on the other hand. We were not the center of the universe, not even the Sun was the center of the universe, not everything revolved around one of those two stars, as the paradigm of the time established. Around a “wandering star”, Jupiter, Galileo discovered four new stars, to which he gave numerical names, Jupiter I-IV, but later they were left with names of four of the “lovers” of the Greek analogue, Zeus: Io, Europa, Ganymede and Callisto. These names were given to them by a German astronomer, Simon Marius, who claimed to have discovered Jupiter’s moons a month before Galileo, and was also accused of plagiarism by Galileo (we leave the surprising resolution of this dispute to the curiosity of our readers). One of those satellites, that Galilei and / or Marius saw in that year 1610 so fascinating and revolutionary, proving that they were not stars and showing that not everything revolves around our navel, it is Jupiter II for Galilei, baptized as Europa by Marius, which is as we know it today.

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Europa is one of the four so-called Galilean moons of Jupiter, the smallest of them, but even so, it is the sixth Largest satellite in the Solar System, slightly smaller than the Moon with about 3100 km in diameter, almost the size from North to South of our continent Europe. Until almost 50 years ago, the satellite was one of the Jupiter and the Solar System, but when we began to visit its surroundings with missions like Pioneer 10 and 11, and especially with the Voyagers or the Galileo probe itself, this satellite gained interest for astrophysicists and for humanity in general. And it is that these missions revealed a world of smooth shapes, without mountains or remnants of meteorite impacts like those we see on the Moon, for example, which implied that its surface is relatively young. That surface must be a few tens or even a few 200 million years, that is, has renewed in the time that mammals have been on Earth.

Another very curious characteristic of Europa is that it reflects almost the 65% of the sunlight that reaches it, a value very similar to the amount of light reflected by the ice in the polar caps of the Land. Images of Voyager 2 (of 1979, a year that is closer to WWII, which seems so far away! , which today!) showed a surface full of plates and bands that seemed the result of fractures of a solid material, filled with a more fluid material, such as lava or water. Measurements of the moon’s magnetic field, provided by the Galileo probe, implied the existence of a material that conducts electricity within it. Apart from these observations, the global density of this moon also suggests that Europa is made up of a core of rocks, similar to those found on a planet like Earth, but surrounded by a large amount of water, perhaps more than twice as large. that our planet has, and with dissolved salts, a great subglacial ocean. That water would be in solid form on the surface, where temperatures are freezing, less than 200 ºC below zero, forming a layer of about 20 kilometers , and liquid underneath, with a great ocean up to 150 kilometers deep.

More recent observations of the satellite, made for example by Hubble only a few years ago, supported this model through the discovery of plumes of water in a gaseous state that would be expelled by what are called cryovolcanoes . Cryovolcanoes are like geysers we have on Earth, but they can form volcanic cones, that is, mountains. They are like our volcanoes, so dramatic this week, but not rock / lava but ice / water. Not only that, Hubble also found indications, yet to be confirmed, of the presence of a thin atmosphere in Europa, composed mainly of oxygen, which perhaps comes from the destruction of water molecules on the surface, continuously bombarded by photons and charged particles. and redirected to Europa by the intense magnetic field of Jupiter.

An ocean interacting with a rocky bottom with geological activity has already been identified on Earth as one of the possible cradles of life. This could be the case in Europe as well. Taking into account that the planet Jupiter has been key in the evolution of the Solar System, it is possible that satellites such as Europa are much more important than we could conceive to know the origins of life on Earth. Being much more imaginative, and remembering the monolith in 2001: Odyssey in space or the theme of the latest films in the Alien saga, such as Covenant, perhaps the cradle of life must be sought beyond our planet. In any case, Europe is fascinating, you have to go there! And in this they are already very advanced projects such as Europa Clipper or JUICE, and others that could happen in 15 – 20 years, like Europa Lander.

Pablo G. Pérez González is a researcher at the Center of Astrobiology, dependent on the Higher Council for Scientific Research and the National Institute of Aerospace Technology (CAB / CSIC-INTA)

Cosmic Void It is a section in which our knowledge about the universe is presented in a qualitative and quantitative way. It is intended to explain the importance of understanding the cosmos not only from a scientific point of view but also from a philosophical, social and economic point of view. The name “cosmic vacuum” refers to the fact that the universe is and is, for the most part, empty, with less than 1 atom per cubic meter, despite the fact that in our environment, paradoxically, there are quintillion atoms per meter cubic, which invites us to reflect on our existence and the presence of life in the universe. The section is made up of Pablo G. Pérez González , researcher at the Center for Astrobiology; Patricia Sánchez Blázquez , tenured professor at the Complutense University of Madrid (UCM); and Eva Villaver , researcher at the Center for Astrobiology

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