When, in 1979, the American probes Voyager-1 and 2 flew over Jupiter and its procession of moons, the images they sent of one of them, Europa, were surprising: this satellite, a little smaller than our Moon, does not seem like it. at all. There are no large volcanic eruptions or craters, but an intriguing bluish and smooth surface, crossed by fracture lines of a color that tends to reddish brown.
Europa is a ball of ice whose crust is cracking under the tidal effect imposed by the mass of the giant planet. Scientists quickly become convinced that ice covers a global ocean. But, also, that it rises to the surface through rectilinear cracks and that the reddish deposits are witnesses of this. The oceanic promise is then combined with a tantalizing scenario: what if life were possible there? To explore this hypothesis, NASA is launching an ambitious mission called “Europa Clipper,” which left Earth on Monday, October 14, aboard a SpaceX Falcon Heavy rocket.
Europa Clipper departs a year and a half after Juice, a European Space Agency (ESA) mission whose main objective is another Jupiter satellite, Ganymede, also equipped with a buried ocean. This madness for these icy moons and this hope for extraterrestrial life may be surprising if we take into account that the Jovian environment is not the most welcoming, full of radiation and, above all, far from the Sun: there we receive the background of our star twenty . -five times less energy than on Earth.
Nothing serious really. The discovery of black smokers at the bottom of the Earth’s oceans, where total darkness reigns, caused “a paradigm shift in the question of habitability: we had life and an entire ecosystem without the slightest light, explains Arnaud Boutonnet, Juice mission analyst at ESA. Life requires liquid water, contact with rocky soil for nutrients and a source of energy. » In the absence of the Sun, the tidal effects experienced by Jupiter’s moons provide them with this energy.
Possible lakes
As Gina DiBraccio, director of NASA’s planetary science division, assures, “Scientists believe that Europa is one of the most promising places for the search for life beyond Earth. But let’s be clear: Clipper will not search for life itself but will characterize the habitability of Europe. »
The probe will not land, drill through ice, or dive into the ocean. Once in orbit around Jupiter, in 2030, it will simply fly regularly over the satellite and analyze it from all angles using its nine instruments, including a radar whose mission will be to describe the structure of the crust and search for the presence of possible lakes. inside him. Another main task assigned to the probe: understanding the composition of Europa and the reddish-brown materials seen there, determining the depth of the ocean, its salinity and its interactions with the surface.
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