Ever since modern science discovered that our place in the universe is quite discrete, humans have wondered if there could be other civilizations like ours somewhere in the cosmos. This possibility ceased to belong to the field of philosophy and became science in the mid-1990s. Specifically, on October 6, 1995, the date on which Michel Mayor and Didier Queloz announced the discovery of the first planet orbiting a solar-type star, 51 Pegasi B.
Since its discovery 24 years ago, more than 4,000 new exoplanets have been found , constituting one of the most promising lines of research of the 21st century and making both researchers worth half of the Nobel Prize in Physics in 2019.
Despite the hopeful number of exoplanets found so far, astrophysicists have explored only a brief fraction of the cosmos. Although the technology in large stellar telescopes has evolved a lot in the last 20 years, the limitations of the human being in terms of space exploration are still considerable. This is reaffirmed by a new simulation model from the University of Chicago and NASA: it suggests that there could be much more life out there than we can detect.
In the search for life on other planets, it is common for scientists to try to locate candidates on planets similar to Earth. Examples of this are some rocky planets located in the Trappist system: they are rock planets (the gaseous ones are discarded), of a size similar to that of the Earth, at a distance from their star within the habitable strip (neither too close nor too away) with liquid water, and with an atmosphere. We seek, like Goldilocks, a planet adjusted to life as we know it.
But we forget that life, as it exists on Earth, can survive in very extreme hot and cold conditions, in volcanoes, in radioactive environments … This means that we cannot rule out environments that can be instinctively hostile as candidates for life, even for life forms with a non-carbon base.
Furthermore, by looking at other solar systems we may miss what is going on in our own neighborhood : places like Europa (Jupiter’s largest moon), which probably houses a liquid sea under a thick layer of ice; o Titan (one of Saturn’s moons), which has continents and seas of methane, could host life forms.
Requirement: a nutritious broth of life
Taking as a reference life on Earth, which is the only thing we know, we know the primitive soup of life was created in the oceans . Therefore, we can agree that water is the elemental requirement in the search for life on other planets. But it all depends on how this water is presented, as explained in this Nobbot article. For geochemist Stephanie Olson, from the University of Chicago: “Not all oceans are equally hospitable. Some oceans are better places to live than others because of their global circulation patterns, ”that is, nutrient circulation systems.
Using a NASA ROCKE-3D computer modeling tool, Olson’s team was able to simulate the atmospheric and oceanic circulation patterns of a multitude of planets, in order to identify the extraterrestrial oceans with the greatest capacity to host abundant and active life.
In the case of Earth, life depends on upward currents of nutrients, from the abyssal depths to the upper areas , where there is sunlight. These streams are called outcrops. “More outcrops imply more replenishment of nutrients and, therefore, more biological activity.”
These are the conditions that we must look for in exoplanets: not only that they have water, but that in these waters there is a good recycling of nutrients , which ensures a good breeding ground for life.
Another of the conclusions of the study was that for these outcrops to occur, certain conditions are more favorable than others ; in particular, the high atmospheric density, slow rotation and the presence of surface continents. This means that perhaps there is some rocky planet even more suitable for life than Earth itself.
Searching for life exactly as we know it is limiting, like searching for a needle in a cosmic haystack. Therefore, we may be leaving out of the equation other equally favorable conditions for life. We just have to open our mind, and the lens of our space telescope.
