one of the great scientific aspirations for the next few decades is the discovery of extraterrestrial life. Very soon, the resolution of the new space telescope James Webb It will allow us to know the composition of the atmospheres of planets light years from Earth and then begin to look for signs of biological activity. The initial temptation, given that our planet is the only living thing in the known universe, is to trace these signals back into systems like the Sun, with stars of similar luminosity, and into planets like the Earth, rocky and with a certain amount of water. , but not too much. However, what we do know of the more than 4,000 identified extrasolar planets is that the home of the first extraterrestrial being will likely have very different conditions from ours.
First of all, we know that three out of four stars of the Milky Way are red dwarfs, much darker than the Sun and also more unstable, but of an abundance which multiplies the chances that life, although with different traits from that which we know, is around they. In addition, the characteristics of these planetary systems, with several planets crammed into orbits closer to the star than that of Mercury, and a sun that does not blind telescopes studying its companions, facilitate observation.
In a study that more precisely classifies the field of research of these habitable planets, two Spanish researchers, Rafael Luque, of the Institute of Astrophysics of Andalusia, and Enric Pallé, of the Institute of Astrophysics of the Canary Islands, have just concluded, based on the analysis of 43 exoplanets, that there is an abundant third group of worlds alongside rocky worlds, like Earth, or gas giants, like Jupiter. Watery planets, with up to 50% of their mass made up of water, are probably as abundant as rocky ones and offer exciting possibilities for supporting life.
In his book published today in the review Science, The researchers studied the density of these 43 worlds in detail and discovered that many of them were too light to be made of only rock. “We saw that planet density, not radius as previously thought, was what separated dry planets from wet ones,” says Luque. This data suggests that half of some of these planets must be water or something lighter.
“Although the Earth is covered in oceans, it is a very dry planet, with only 0.02% water”, explains the researcher from the University of Chicago. “These aquatic worlds have, perhaps, half the water, but as far as we know it cannot be on the surface, distributed as on Earth, around a rocky core, because, being so close to the star, the water would evaporate.” There, the water would end up in the inland oceans, covered by the crust, or trapped in the magma,” continues Luque. These worlds so close to their star, as is the case with the Moon or Mercury, are blocked by tidal forces which force them to always show the same side to the star. This means that one side of the planet is always frozen and the other is a real hell, although there are theoretical models that open the possibility that inside the planet the temperature distribution is more homogeneous.
Guillem Anglada Escudé, researcher of Institute of Space Sciences from CSIC, which was not involved in the work, calls the results “important” because they help clarify the different populations of planets that orbit these stars. “Plus,” he adds, “it helps put the Earth in the context of all possible planetary systems.” In our solar system, the distribution of planets is relatively infrequent, if we take into account the known exoplanets, with a clear spatial distribution, with the exterior of the system for the gas giants and the interior for the rockies. Here too there are aquatic worlds, with immense underground oceans under an icy crust, like Ganymede and Europa, the moons of Jupiter, or Titan and Enceladus, the satellites of Saturn. On the worlds studied, it is likely that the oceanic planets formed by accumulating ice far from their star and then migrating through the planetary system, to orbits very close to their star. In the case of the solar system, the rapid formation of giants such as Jupiter or Saturn created a gravitational barrier which prevented a possible approach of Uranus or Neptune in the vicinity of the Sun.
With a star like ours, in an orbit smaller than that of Mercury, the temperature would be scorching, but with red dwarfs, like our neighbor Proxima Centauri or the trappist system-1 “There would be a hot temperature,” recalls Anglada Escudé. “Allí, en un par de años, vamos a poder empezar a detectar moléculas básicas, como el agua o el carbono, y después, podremos ver, por ejemplo, si en un planeta hay un excess de CO₂ respecto a lo que se ve en others. With this comparison, we can ask ourselves if this difference has its origin in a certain type of biological activity”, he concludes.
In 1961, long before the first detection of a planet outside the solar system, the Polish writer Stanislaw Lem published the story of Solaris, a world covered almost entirely by the ocean which was at the same time a form of life intelligent with the that humans, despite a century of effort, could not communicate. Three decades later, a compatriot of Lem, Aleksander Wolszczan, detected the first two extrasolar planets, two ghostly worlds, with three times the mass of the Earth, revolving around a pulsar, a neutron star which after exhausting its fuel had collapsed under its own gravitational pull. As well as exciting the imagination, the painstaking real-world work that does exist, such as that published today by Luque and Pallé, may hold surprises in the years to come that rival literary speculation.
you can follow MATERIAL in Facebook, Twitter e instagramthe apuntarte here to receive our weekly newsletter.